Subject: Re: [teres] Motor/pulley/controller/supply "kit" Date: Sat, 19 Feb 2000 00:56:18 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: Thom Mackris (h) ----- Original Message ----- From: steve brooks To: Sent: Friday, February 18, 2000 10:53 PM Subject: Re: [teres] Motor/pulley/controller/supply "kit" Chris, Count me in for the motor kit also. There are a couple of things I would like to put up for discussion. Number 1, Is there any benefit to buying the more expensive Maxon motor that was written about in SP 10? I realize it is quite a bit more expensive but I don't want to go this far and regret not spending the extra $175 or so. I remember Manfred mentioning it, but I don't know a thing about motors, so I'm not clear on the differences. And number 2, in that same SP article all the Platine folks were using recording tape instead of a rubber belt...the thinking is that the motor is so still that you don't need the isolation that the rubber belt provides and also the tape gives you maximum contact with the pulley. Steve PS Joe Roberts, while giving me permission to post the photos from said article, also offered to us for experimenting, the three East German motors that the author tested. Of course he dumped them all for the Maxon. > David, > > So far 22 have expressed an interest in the motor/controller kit. This is > enough to keep the cost of the motors and circuit boards down and make the > kits feasible. Based on the level of interest I intend to make the kits > available. > > Chris Subject: Re: [teres] Motor/pulley/controller/supply "kit" Date: Sat, 19 Feb 2000 01:01:53 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: Thom Mackris (h) ----- Original Message ----- From: steve brooks To: Sent: Friday, February 18, 2000 10:53 PM Subject: Re: [teres] Motor/pulley/controller/supply "kit" Chris, Count me in for the motor kit also. There are a couple of things I would like to put up for discussion. Number 1, Is there any benefit to buying the more expensive Maxon motor that was written about in SP 10? I realize it is quite a bit more expensive but I don't want to go this far and regret not spending the extra $175 or so. I remember Manfred mentioning it, but I don't know a thing about motors, so I'm not clear on the differences. And number 2, in that same SP article all the Platine folks were using recording tape instead of a rubber belt...the thinking is that the motor is so still that you don't need the isolation that the rubber belt provides and also the tape gives you maximum contact with the pulley. Steve PS Joe Roberts, while giving me permission to post the photos from said article, also offered to us for experimenting, the three East German motors that the author tested. Of course he dumped them all for the Maxon. > David, > > So far 22 have expressed an interest in the motor/controller kit. This is > enough to keep the cost of the motors and circuit boards down and make the > kits feasible. Based on the level of interest I intend to make the kits > available. > > Chris Subject: Re: [teres] Motor/pulley/controller/supply "kit" Date: Sat, 19 Feb 2000 03:49:04 -0700 From: Manfred Huber, Manfred Huber To: teres@aiko.com Steve, >Is there any benefit to buying the more expensive Maxon motor that was >written about in SP 10? I have already posted my view on this here on the list. To sum it up: There are pros and cons to each of the motors. From the published technical data I can see no reason why the more expensive S-motor should perform better. Yet I did not verify this in practice. >I realize it is quite a bit more expensive but I don't want to go this far >and regret not spending the extra $175 or so. I don't know where the very high price given in the SP article is coming from. When I asked Maxon here in Germany for prices the S-Motor was about $20 more expensive than the A-Max. >And number 2, in that same SP article all the Platine folks were using recording tape >instead of a rubber belt...the thinking is that the motor is so still that >you don't need the isolation that the rubber belt provides and also the tape >gives you maximum contact with the pulley. I also use 1/4" magnetic tape and like it better when compared to a thin string. The differences are subtle and I guess it is a matter of taste what one likes better. Try different materials and see what you like best. For those wanting to try the mag. tape: I did much experimentation on how to join the ends of the tape to form a loop. The best method I found is to use a type of cyanacrylate glue that stays flexible after it has dried. Using this stuff you only need 2mm of overlap and the joint does not stiffen. Someone once told me that you can use acetone to remove the magnetic particles and get a clear film but I did not try this yet. Regards Manfred. ------------------ Manfred Huber MHuber@t-online.de ------------------ Subject: Re: [teres] Motor/pulley/controller/supply "kit" Date: Sat, 19 Feb 2000 11:01:19 -0700 From: Chris Brady, Chris Brady To: teres@aiko.com I received the Maxxon catalogue yesterday and have been researching other motor possibilities. Using the criteria from the SP "Turn Your Table" article I came up with 7 candidates. I called for a price for each of the motors, but have not heard back yet. Here's a list of the motors and their specs. Pgm Part# MI STG rpm/V RadF Watts ===================================================================== RE-Stk 118690 1.15 414 304 1.5 3.2 RE-Std 118691 1.10 432 217 1.5 3.2 RE-Stk 118746 10.3 37.5 218 16.0 10.0 S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 AX-Stk 110189 11.8 103 180 5.5 7.0 AX-Stk 110212 11.8 103 180 5.5 4.5 Legend: Pgm This is a motor series. RE is the top of the line and uses Neodymium magnets. The S series is next to the top and uses Alnico magnets. AX is for the A-Max series and is the same as the S series in a more economical package. MI Moment of inertia. Less is better and the SP article suggested values less than 10. STG Speed/torque gradient. This is an indication of the motors power. It is a measure of the motors ability to maintain constant speed with load variations. Less is better and the SP article suggested values of less than 1000 and implied that less than 500 is needed for heavier platters. rpm/V RPM per volt. Values of 150 to 300 work well. RadF Allowable radial force. Part number 110189 is what Manfred suggested. It's moment of intertial is on the high side, but it is quite powerful. The 110212 has the same specs but a lower power rating and may be less expensive. Part number 2326-942-12-111-050 is the motor recommended in the SP article. It has a different intertia/power balance that may be better for our moderately heavy platter. The RE 118746 is really impressive. Lower inertia than the 110189 and 3 times as powerful! This is probably very pricy. The RE 118690 and 118691 motors are a little weak but the moment of inertia is remarkably low. The RE series motors are clearly the best, but the prices may be prohibitive. I don't know which of the two would offer the best inertia/power compromise. I'll send out the pricing info when I get it. Chris steve brooks wrote: > > Chris, > Count me in for the motor kit also. There are a couple of things I would > like to put up for discussion. Number 1, Is there any benefit to buying the > more expensive Maxon motor that was written about in SP 10? I realize it is > quite a bit more expensive but I don't want to go this far and regret not > spending the extra $175 or so. I remember Manfred mentioning it, but I don't > know a thing about motors, so I'm not clear on the differences. And number > 2, in that same SP article all the Platine folks were using recording tape > instead of a rubber belt...the thinking is that the motor is so still that > you don't need the isolation that the rubber belt provides and also the tape > gives you maximum contact with the pulley. > Steve > > PS Joe Roberts, while giving me permission to post the photos from said > article, also offered to us for experimenting, the three East German motors > that the author tested. Of course he dumped them all for the Maxon. > > > David, > > > > So far 22 have expressed an interest in the motor/controller kit. This is > > enough to keep the cost of the motors and circuit boards down and make the > > kits feasible. Based on the level of interest I intend to make the kits > > available. > > > > Chris Subject: Re: [teres] Motor/pulley/controller/supply "kit" Date: Sat, 19 Feb 2000 13:01:29 -0700 From: Manfred Huber, Manfred Huber To: teres@aiko.com Chris, I also had a look at these motors. here is my view: >RE-Stk 118690 1.15 414 304 1.5 3.2 >RE-Std 118691 1.10 432 217 1.5 3.2 nice performers. I decided not to use them because of the low allowable radial force of only 1.5 Newton. I consider this too low especially when it with magnetic tape. >RE-Stk 118746 10.3 37.5 218 16.0 10.0 This is a killer motor! Unfortunately according to my catalogue it is only available with ball bearings. >S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 No doubt this is a good candidate. I prefer the other S-Motor for its higher allowable bearing forces and because IMHO the other motors are more 'agile' (see below) >S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 >AX-Stk 110189 11.8 103 180 5.5 7.0 This is the one I chose. >AX-Stk 110212 11.8 103 180 5.5 4.5 This motor is very much the same as the one I use. Main difference is that is has a long shaft comes out of the housing on both sides. I considered this inconvenient as I had no use for a shaft on the opposite side of the pulley and it makes the motor bigger. > MI Moment of inertia. Less is better and the SP article > suggested values less than 10. Here I have a different opinion. It is not the inertia alone that counts. The inertia has to be set in relation to the power of the motor. The best measure for this is the mechanical time constant of the motor. (ie. the time the motor needs to come up to 68% of it's nominal speed. If you look at the data in the Maxon catalogue you will see that the S-Motor suggested by the SP article and the A-Max I use perform pretty much the same in this regard. >Part number 2326-942-12-111-050 is the motor recommended in the SP article. >It has a different intertia/power balance that may be better for our >moderately heavy platter. This also depends on the size of pulley you want to use. The A-Motor is more powerful than the S-Motor but I use it with a pulley that has more diameter than what is recommended in the SP article. This way I get lower rpm and lower mechanical noise and better friction. >The RE 118690 and 118691 motors are a little weak but the moment of >inertia is remarkably low. Yes, and with a time constant of only 5ms the are very agile! I think these may be the best choice if you can get away with the low allowable bearing forces. Regards Manfred ------------------ Manfred Huber MHuber@t-online.de ------------------ Subject: Re: [teres] Motor/pulley/controller/supply "kit" Date: Sat, 19 Feb 2000 13:58:54 -0700 From: Igor Kuznetsoff, Igor Kuznetsoff To: teres@aiko.com Thorough analysis, Manfred, thank you. Igor --- Manfred Huber wrote: > Chris, > > I also had a look at these motors. here is my view: > > >RE-Stk 118690 1.15 414 304 > 1.5 3.2 > >RE-Std 118691 1.10 432 217 > 1.5 3.2 > > nice performers. I decided not to use them because > of the low allowable > radial force of only 1.5 Newton. I consider this too > low especially when > it with magnetic tape. > > >RE-Stk 118746 10.3 37.5 218 > 16.0 10.0 > > This is a killer motor! Unfortunately according to > my catalogue it is only > available with ball bearings. > > >S-Std 2522-941-12-112-000 3.47 495 199 > 2.8 3.8 > > No doubt this is a good candidate. I prefer the > other S-Motor for > its higher allowable bearing forces and because IMHO > the other motors > are more 'agile' (see below) > > >S-Stk 2326-942-12-111-050 7.77 206 203 > 4.3 4.0 > > >AX-Stk 110189 11.8 103 180 > 5.5 7.0 > > This is the one I chose. > > >AX-Stk 110212 11.8 103 180 > 5.5 4.5 > > This motor is very much the same as the one I use. > Main difference is > that is has a long shaft comes out of the housing on > both sides. > I considered this inconvenient as I had no use for a > shaft on the > opposite side of the pulley and it makes the motor > bigger. > > > > MI Moment of inertia. Less is better and the SP > article > > suggested values less than 10. > > Here I have a different opinion. It is not the > inertia alone that counts. > The inertia has to be set in relation to the power > of the motor. The best > measure for this is the mechanical time constant of > the motor. (ie. the time > the motor needs to come up to 68% of it's nominal > speed. If you look at the data > in the Maxon catalogue you will see that the S-Motor > suggested by the SP article > and the A-Max I use perform pretty much the same in > this regard. > > >Part number 2326-942-12-111-050 is the motor > recommended in the SP article. > >It has a different intertia/power balance that may > be better for our > >moderately heavy platter. > > This also depends on the size of pulley you want to > use. The A-Motor > is more powerful than the S-Motor but I use it with > a pulley that has more > diameter than what is recommended in the SP article. > This way I get lower > rpm and lower mechanical noise and better friction. > > >The RE 118690 and 118691 motors are a little weak > but the moment of > >inertia is remarkably low. > > Yes, and with a time constant of only 5ms the are > very agile! > I think these may be the best choice if you can get > away with the low > allowable bearing forces. > > Regards > Manfred > > > ------------------ > Manfred Huber > MHuber@t-online.de > ------------------ > > > __________________________________________________ Do You Yahoo!? Talk to your friends online with Yahoo! Messenger. http://im.yahoo.com Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sat, 19 Feb 2000 21:34:42 -0700 From: Sellek, Grant (TSA), Sellek, Grant (TSA) To: 'teres@aiko.com' I suppose I missed a huge discussion of motors, although I have seen some threads (I recall mention of "cogging" issues, for example). And I don't know much about motors, so I cannot develop what I write below into a real argument. But I must ask: Why are you using the criteria from Wilimzig's article in SP#10? When I saw Verdier's reply in SP#11, I decided that Wilimzig fell for a trap described in Joenet this week as "an internally consistent argument that does not meet the conditions of reality". Verdier wrote that low inertia is "not that interesting of a quality for a turntable's motor". The fact that the Platine Verdier's motor is low-inertia is apparently not its main attribute. He also wrote that if Wilimzig's assumption were true, (that it is the motor's job to instantaneously correct platter speed variations caused by the action of the stylus in the groove), then no turntable could work well, because no motor is good enough. Verdier's solution to this issue has, it seems to me, nothing to do with the motor: he uses the rotational inertia of a massive platter, plus a constant-coupled brake system to ensure the variations in energy from the stylus into the platter is "swamped" by a high-energy system. I don't believe that these tiny motors will have any useful "instantaneous correction" effect in a high-energy system, such as the Teres platter and bearing with viscous oil. You would have to greatly lower the energy of the system to let the motor try its luck. I will be taking my Teres along the path suggested by Verdier in this particular regard. That means the criteria become low-noise bearings and brushes, along with high linearity and sufficient power for a high-energy environment (by turntable standards). OK, shred me. I honestly don't know much about electric motors. Grant Grant Sellek Adelaide, Australia grant.sellek@transport.sa.gov.au -----Original Message----- From: Chris Brady [mailto:cbrady@sgi.com] Sent: Sunday, 20 February 2000 3:30 AM To: teres@aiko.com Subject: Re: [teres] Motor/pulley/controller/supply "kit" I received the Maxxon catalogue yesterday and have been researching other motor possibilities. Using the criteria from the SP "Turn Your Table" article I came up with 7 candidates. I called for a price for each of the motors, but have not heard back yet. Here's a list of the motors and their specs. Pgm Part# MI STG rpm/V RadF Watts ===================================================================== RE-Stk 118690 1.15 414 304 1.5 3.2 RE-Std 118691 1.10 432 217 1.5 3.2 RE-Stk 118746 10.3 37.5 218 16.0 10.0 S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 AX-Stk 110189 11.8 103 180 5.5 7.0 AX-Stk 110212 11.8 103 180 5.5 4.5 Legend: Pgm This is a motor series. RE is the top of the line and uses Neodymium magnets. The S series is next to the top and uses Alnico magnets. AX is for the A-Max series and is the same as the S series in a more economical package. MI Moment of inertia. Less is better and the SP article suggested values less than 10. STG Speed/torque gradient. This is an indication of the motors power. It is a measure of the motors ability to maintain constant speed with load variations. Less is better and the SP article suggested values of less than 1000 and implied that less than 500 is needed for heavier platters. rpm/V RPM per volt. Values of 150 to 300 work well. RadF Allowable radial force. Part number 110189 is what Manfred suggested. It's moment of intertial is on the high side, but it is quite powerful. The 110212 has the same specs but a lower power rating and may be less expensive. Part number 2326-942-12-111-050 is the motor recommended in the SP article. It has a different intertia/power balance that may be better for our moderately heavy platter. The RE 118746 is really impressive. Lower inertia than the 110189 and 3 times as powerful! This is probably very pricy. The RE 118690 and 118691 motors are a little weak but the moment of inertia is remarkably low. The RE series motors are clearly the best, but the prices may be prohibitive. I don't know which of the two would offer the best inertia/power compromise. I'll send out the pricing info when I get it. Chris Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sat, 19 Feb 2000 21:53:29 -0700 From: phclark, phclark To: teres@aiko.com Thanks, Grant, for articulating a concern I had when I read the Verdier comments a couple of years ago. Of course, at that time I did not anticipate owning a hot rod table in my lifetime, and figured that anybody who could market an 8k 'table could pretty much say anything he damn well pleased, sensible or not. Verdier's comments struck me at the time to be counterintuitive if not outright incorrect. Having examined the development of the Teres table from Chris' website, my cocktail napkin figgerin' agreed conceptually, and I decided I'd let smarter people than me do the heavy lifting. Same with the motor/controller assembly. Grant's question has certain moment, and if it's not too akin to handholding, I'd appreciate some commentary about his concerns as well. More Anxious in Scottsdale, Peter C ----- Original Message ----- From: "Sellek, Grant (TSA)" To: Sent: Saturday, February 19, 2000 8:32 PM Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? > I suppose I missed a huge discussion of motors, although I have seen some > threads (I recall mention of "cogging" issues, for example). And I don't > know much about motors, so I cannot develop what I write below into a real > argument. But I must ask: > > Why are you using the criteria from Wilimzig's article in SP#10? When I saw > Verdier's reply in SP#11, I decided that Wilimzig fell for a trap described > in Joenet this week as "an internally consistent argument that does not meet > the conditions of reality". > > Verdier wrote that low inertia is "not that interesting of a quality for a > turntable's motor". The fact that the Platine Verdier's motor is low-inertia > is apparently not its main attribute. He also wrote that if Wilimzig's > assumption were true, (that it is the motor's job to instantaneously correct > platter speed variations caused by the action of the stylus in the groove), > then no turntable could work well, because no motor is good enough. > > Verdier's solution to this issue has, it seems to me, nothing to do with the > motor: he uses the rotational inertia of a massive platter, plus a > constant-coupled brake system to ensure the variations in energy from the > stylus into the platter is "swamped" by a high-energy system. > > I don't believe that these tiny motors will have any useful "instantaneous > correction" effect in a high-energy system, such as the Teres platter and > bearing with viscous oil. You would have to greatly lower the energy of the > system to let the motor try its luck. I will be taking my Teres along the > path suggested by Verdier in this particular regard. That means the criteria > become low-noise bearings and brushes, along with high linearity and > sufficient power for a high-energy environment (by turntable standards). > > OK, shred me. I honestly don't know much about electric motors. > Grant > > > Grant Sellek > Adelaide, Australia > grant.sellek@transport.sa.gov.au > > > -----Original Message----- > From: Chris Brady [mailto:cbrady@sgi.com] > Sent: Sunday, 20 February 2000 3:30 AM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" > > > I received the Maxxon catalogue yesterday and have been researching other > motor possibilities. Using the criteria from the SP "Turn Your Table" > article I came up with 7 candidates. I called for a price for each of > the motors, but have not heard back yet. Here's a list of the motors > and their specs. > > Pgm Part# MI STG rpm/V RadF Watts > ===================================================================== > RE-Stk 118690 1.15 414 304 1.5 3.2 > RE-Std 118691 1.10 432 217 1.5 3.2 > RE-Stk 118746 10.3 37.5 218 16.0 10.0 > > S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 > S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 > > AX-Stk 110189 11.8 103 180 5.5 7.0 > AX-Stk 110212 11.8 103 180 5.5 4.5 > > Legend: > Pgm This is a motor series. RE is the top of the line and > uses Neodymium magnets. The S series is next to the > top and uses Alnico magnets. AX is for the A-Max series > and is the same as the S series in a more economical > package. > > MI Moment of inertia. Less is better and the SP article > suggested values less than 10. > > STG Speed/torque gradient. This is an indication of the motors > power. It is a measure of the motors ability to maintain > constant speed with load variations. Less is better and the > SP article suggested values of less than 1000 and implied > that less than 500 is needed for heavier platters. > > rpm/V RPM per volt. Values of 150 to 300 work well. > > RadF Allowable radial force. > > Part number 110189 is what Manfred suggested. It's moment of intertial is > on the high side, but it is quite powerful. The 110212 has the same specs > but a lower power rating and may be less expensive. > > Part number 2326-942-12-111-050 is the motor recommended in the SP article. > It has a different intertia/power balance that may be better for our > moderately heavy platter. > > The RE 118746 is really impressive. Lower inertia than the 110189 and 3 > times as powerful! This is probably very pricy. > > The RE 118690 and 118691 motors are a little weak but the moment of > inertia is remarkably low. > > The RE series motors are clearly the best, but the prices may be > prohibitive. > I don't know which of the two would offer the best inertia/power compromise. > > I'll send out the pricing info when I get it. > > Chris > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sat, 19 Feb 2000 22:24:51 -0700 From: Sellek, Grant (TSA), Sellek, Grant (TSA) To: 'phclark@uswest.net' CC: 'Teres List' Peter, I am slightly confused by your comment. I think the confusion is because there are TWO articles under discussion: one by Wilimzig in SP#10 about his Platine Verdier, that I disagree with, and a reply by Verdier in SP#11, that I agree with. Since I agree with Verdier, I am confused when you say you agree with me but disagree with Verdier! I *suspect* that you agree (tentatively) with me and therefore with Verdier, and disagree with the Wilimzig article in SP#10 that is the basis of much of this low-inertia emphasis. But don't let me put words in your mouth. Grant Grant Sellek Adelaide, Australia grant.sellek@transport.sa.gov.au -----Original Message----- From: phclark [mailto:phclark@uswest.net] Sent: Sunday, 20 February 2000 2:09 PM To: teres@aiko.com Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Thanks, Grant, for articulating a concern I had when I read the Verdier comments a couple of years ago. Of course, at that time I did not anticipate owning a hot rod table in my lifetime, and figured that anybody who could market an 8k 'table could pretty much say anything he damn well pleased, sensible or not. Verdier's comments struck me at the time to be counterintuitive if not outright incorrect. Having examined the development of the Teres table from Chris' website, my cocktail napkin figgerin' agreed conceptually, and I decided I'd let smarter people than me do the heavy lifting. Same with the motor/controller assembly. Grant's question has certain moment, and if it's not too akin to handholding, I'd appreciate some commentary about his concerns as well. More Anxious in Scottsdale, Peter C ----- Original Message ----- From: "Sellek, Grant (TSA)" To: Sent: Saturday, February 19, 2000 8:32 PM Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? > I suppose I missed a huge discussion of motors, although I have seen some > threads (I recall mention of "cogging" issues, for example). And I don't > know much about motors, so I cannot develop what I write below into a real > argument. But I must ask: > > Why are you using the criteria from Wilimzig's article in SP#10? When I saw > Verdier's reply in SP#11, I decided that Wilimzig fell for a trap described > in Joenet this week as "an internally consistent argument that does not meet > the conditions of reality". > > Verdier wrote that low inertia is "not that interesting of a quality for a > turntable's motor". The fact that the Platine Verdier's motor is low-inertia > is apparently not its main attribute. He also wrote that if Wilimzig's > assumption were true, (that it is the motor's job to instantaneously correct > platter speed variations caused by the action of the stylus in the groove), > then no turntable could work well, because no motor is good enough. > > Verdier's solution to this issue has, it seems to me, nothing to do with the > motor: he uses the rotational inertia of a massive platter, plus a > constant-coupled brake system to ensure the variations in energy from the > stylus into the platter is "swamped" by a high-energy system. > > I don't believe that these tiny motors will have any useful "instantaneous > correction" effect in a high-energy system, such as the Teres platter and > bearing with viscous oil. You would have to greatly lower the energy of the > system to let the motor try its luck. I will be taking my Teres along the > path suggested by Verdier in this particular regard. That means the criteria > become low-noise bearings and brushes, along with high linearity and > sufficient power for a high-energy environment (by turntable standards). > > OK, shred me. I honestly don't know much about electric motors. > Grant > > > Grant Sellek > Adelaide, Australia > grant.sellek@transport.sa.gov.au > > > -----Original Message----- > From: Chris Brady [mailto:cbrady@sgi.com] > Sent: Sunday, 20 February 2000 3:30 AM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" > > > I received the Maxxon catalogue yesterday and have been researching other > motor possibilities. Using the criteria from the SP "Turn Your Table" > article I came up with 7 candidates. I called for a price for each of > the motors, but have not heard back yet. Here's a list of the motors > and their specs. > > Pgm Part# MI STG rpm/V RadF Watts > ===================================================================== > RE-Stk 118690 1.15 414 304 1.5 3.2 > RE-Std 118691 1.10 432 217 1.5 3.2 > RE-Stk 118746 10.3 37.5 218 16.0 10.0 > > S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 > S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 > > AX-Stk 110189 11.8 103 180 5.5 7.0 > AX-Stk 110212 11.8 103 180 5.5 4.5 > > Legend: > Pgm This is a motor series. RE is the top of the line and > uses Neodymium magnets. The S series is next to the > top and uses Alnico magnets. AX is for the A-Max series > and is the same as the S series in a more economical > package. > > MI Moment of inertia. Less is better and the SP article > suggested values less than 10. > > STG Speed/torque gradient. This is an indication of the motors > power. It is a measure of the motors ability to maintain > constant speed with load variations. Less is better and the > SP article suggested values of less than 1000 and implied > that less than 500 is needed for heavier platters. > > rpm/V RPM per volt. Values of 150 to 300 work well. > > RadF Allowable radial force. > > Part number 110189 is what Manfred suggested. It's moment of intertial is > on the high side, but it is quite powerful. The 110212 has the same specs > but a lower power rating and may be less expensive. > > Part number 2326-942-12-111-050 is the motor recommended in the SP article. > It has a different intertia/power balance that may be better for our > moderately heavy platter. > > The RE 118746 is really impressive. Lower inertia than the 110189 and 3 > times as powerful! This is probably very pricy. > > The RE 118690 and 118691 motors are a little weak but the moment of > inertia is remarkably low. > > The RE series motors are clearly the best, but the prices may be > prohibitive. > I don't know which of the two would offer the best inertia/power compromise. > > I'll send out the pricing info when I get it. > > Chris > Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sat, 19 Feb 2000 23:44:28 -0700 From: phclark, phclark To: teres@aiko.com I confess that I don't have either article in front of me, they're still packed from my not-too-recent move. ----- Original Message ----- From: "Sellek, Grant (TSA)" > > Since I agree with Verdier, I am confused when you say you agree with me but > disagree with Verdier! Not so. The "original" analysis which postulated a motor instantaneously regulating rotation of a "massive" platter to some putative audiophile standard > I *suspect* that you agree (tentatively) with me and therefore with Verdier, > and disagree with the Wilimzig article in SP#10 that is the basis of much of > this low-inertia emphasis. But don't let me put words in your mouth. > > Verdier wrote that low inertia is "not that interesting of a quality for a > > turntable's motor". Agreed, to a point. Low inertia would be valuable for reasons other than fast response. Overcontrolling a motor of low or high inertia would be very undesirable, as it would have a tendency to constantly "hunt" for its preset controller value. I'd far prefer a motor that ran consistently at 33 rpm, a correctable problem, than one that constantly fluctuated on both sides of 33 1/3. > The fact that the Platine Verdier's motor is > low-inertia > > is apparently not its main attribute. He also wrote that if Wilimzig's > > assumption were true, (that it is the motor's job to instantaneously > correct > > platter speed variations caused by the action of the stylus in the > groove), > > then no turntable could work well, because no motor is good enough. > > > > Verdier's solution to this issue has, it seems to me, nothing to do with > the > > motor: he uses the rotational inertia of a massive platter, plus a > > constant-coupled brake system to ensure the variations in energy from the > > stylus into the platter is "swamped" by a high-energy system. This is where Verdier's characterization seemed implausible for a precision instrument. I envisioned your Ferrari flat out in first gear with the brakes on to make sure it never went over 20 mph. > > I don't believe that these tiny motors will have any useful "instantaneous > > correction" effect in a high-energy system, such as the Teres platter and > > bearing with viscous oil. You would have to greatly lower the energy of > the > > system to let the motor try its luck. I will be taking my Teres along the > > path suggested by Verdier in this particular regard. That means the > criteria > > become low-noise bearings and brushes, along with high linearity and > > sufficient power for a high-energy environment (by turntable standards). > > There, that's what I agree with. Indeed, these tiny motors, some of which don't have the power to start the platter unassisted, cannot be expected, of themselves, to regulate rotational speed. It begs the question of using a massive platter as a flywheel. But maybe I'm all wet. Peter C Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 00:40:49 -0700 From: Roscoe Primrose, Roscoe Primrose To: teres@aiko.com "Sellek, Grant (TSA)" wrote: > > I suppose I missed a huge discussion of motors, although I have seen some > threads (I recall mention of "cogging" issues, for example). And I don't > know much about motors, so I cannot develop what I write below into a real > argument. But I must ask: > > Why are you using the criteria from Wilimzig's article in SP#10? When I saw > Verdier's reply in SP#11, I decided that Wilimzig fell for a trap described > in Joenet this week as "an internally consistent argument that does not meet > the conditions of reality". I too thought Wilimzig was wrong in some of his logic.. Since the motor's rotation and the platters rotation are locked together (ideally, and nearly so with something that doesn't stretch) having a motor with low intertia with a heavy platter is a lot like having a diet soda with a pound of butter, it doesn't make a rats ass of difference, it's the intertia of the whole rotating system that matters. > > Verdier wrote that low inertia is "not that interesting of a quality for a > turntable's motor". The fact that the Platine Verdier's motor is low-inertia > is apparently not its main attribute. He also wrote that if Wilimzig's > assumption were true, (that it is the motor's job to instantaneously correct > platter speed variations caused by the action of the stylus in the groove), > then no turntable could work well, because no motor is good enough. Indeed, unless the whole rotating system has inertia approaching zero... > OK, shred me. I honestly don't know much about electric motors. > Grant > Maybe not, but your physics doesn't seem lacking. Peace -- Roscoe Primrose -- mailto:roscoe@aiko.com -- http://www.aiko.com/roscoe -- "Once in a while you get shown the light In the strangest of places if you look at it right." Robert Hunter Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 01:23:35 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: teres@aiko.com Grant, I don't think you missed much on motors, and you have thought this issue out well. I personally don't have a strong enough grasp of the physics and so I find myself waffling on the issue of low inertia motors. With a non-compliant belt (recording tape), it seems as if the platter and the motor are intimately tied to each other and that the only inertia to be considered is the combined inertia of the system of motor & platter. What am I missing here? What really confuses me about this whole issue are the reports of differences between two competent drive systems (motor + controller) as well as between choices of belt material on a 'table like a Verdier. Intuitively, I would think that changes to these parts would not result in audible differences. I would expect that the mass of the platter on the Verdier along with the viscuous braking would control and regulate the speed of the platter. Reports are that mass and braking are not enough, and that the motor and controller must be designed to a very high standard. Are these reports merely those of proud designers who are emotionally wed to their improvements? All of us are vulnerable to this effect - "I struggled to make this change/tweek, it's different, therefor I made an improvement". I agree with Verdier's comments that a motor cannot react to instantaneous speed variations in the platter. The reaction would be much too late and would just smear the signal. I rather see that the only thing that a motor can do is to resist these variations in the first place through a stable power supply along with having enough torque to do the job and a non-compliant belt. As a footnote, early in the bearing dialog we spoke of viscuous damping and designed the well in the center of the bearing specifically for this purpose. Originally, we were just looking to reduce the bearing contact area (less noise) but as we got into it, we expanded this well as much as financially possible in order to effect damping. There was a limit to how big the well could get based on (a) not wanting to leave too thin a wall on the bearing and (b) the price of the next size of brass stock sending the project financially out of control. Confused in Denver (but confident in Manfred) ... Thom ----- Original Message ----- From: Sellek, Grant (TSA) To: Sent: Saturday, February 19, 2000 8:32 PM Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? I suppose I missed a huge discussion of motors, although I have seen some threads (I recall mention of "cogging" issues, for example). And I don't know much about motors, so I cannot develop what I write below into a real argument. But I must ask: Why are you using the criteria from Wilimzig's article in SP#10? When I saw Verdier's reply in SP#11, I decided that Wilimzig fell for a trap described in Joenet this week as "an internally consistent argument that does not meet the conditions of reality". Verdier wrote that low inertia is "not that interesting of a quality for a turntable's motor". The fact that the Platine Verdier's motor is low-inertia is apparently not its main attribute. He also wrote that if Wilimzig's assumption were true, (that it is the motor's job to instantaneously correct platter speed variations caused by the action of the stylus in the groove), then no turntable could work well, because no motor is good enough. Verdier's solution to this issue has, it seems to me, nothing to do with the motor: he uses the rotational inertia of a massive platter, plus a constant-coupled brake system to ensure the variations in energy from the stylus into the platter is "swamped" by a high-energy system. I don't believe that these tiny motors will have any useful "instantaneous correction" effect in a high-energy system, such as the Teres platter and bearing with viscous oil. You would have to greatly lower the energy of the system to let the motor try its luck. I will be taking my Teres along the path suggested by Verdier in this particular regard. That means the criteria become low-noise bearings and brushes, along with high linearity and sufficient power for a high-energy environment (by turntable standards). OK, shred me. I honestly don't know much about electric motors. Grant Grant Sellek Adelaide, Australia grant.sellek@transport.sa.gov.au -----Original Message----- From: Chris Brady [mailto:cbrady@sgi.com] Sent: Sunday, 20 February 2000 3:30 AM To: teres@aiko.com Subject: Re: [teres] Motor/pulley/controller/supply "kit" I received the Maxxon catalogue yesterday and have been researching other motor possibilities. Using the criteria from the SP "Turn Your Table" article I came up with 7 candidates. I called for a price for each of the motors, but have not heard back yet. Here's a list of the motors and their specs. Pgm Part# MI STG rpm/V RadF Watts ===================================================================== RE-Stk 118690 1.15 414 304 1.5 3.2 RE-Std 118691 1.10 432 217 1.5 3.2 RE-Stk 118746 10.3 37.5 218 16.0 10.0 S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 AX-Stk 110189 11.8 103 180 5.5 7.0 AX-Stk 110212 11.8 103 180 5.5 4.5 Legend: Pgm This is a motor series. RE is the top of the line and uses Neodymium magnets. The S series is next to the top and uses Alnico magnets. AX is for the A-Max series and is the same as the S series in a more economical package. MI Moment of inertia. Less is better and the SP article suggested values less than 10. STG Speed/torque gradient. This is an indication of the motors power. It is a measure of the motors ability to maintain constant speed with load variations. Less is better and the SP article suggested values of less than 1000 and implied that less than 500 is needed for heavier platters. rpm/V RPM per volt. Values of 150 to 300 work well. RadF Allowable radial force. Part number 110189 is what Manfred suggested. It's moment of intertial is on the high side, but it is quite powerful. The 110212 has the same specs but a lower power rating and may be less expensive. Part number 2326-942-12-111-050 is the motor recommended in the SP article. It has a different intertia/power balance that may be better for our moderately heavy platter. The RE 118746 is really impressive. Lower inertia than the 110189 and 3 times as powerful! This is probably very pricy. The RE 118690 and 118691 motors are a little weak but the moment of inertia is remarkably low. The RE series motors are clearly the best, but the prices may be prohibitive. I don't know which of the two would offer the best inertia/power compromise. I'll send out the pricing info when I get it. Chris Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 01:33:20 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: teres@aiko.com Peter, I don't think that the Ferrari analogy is applicable to this situation. The thinking behind viscuous braking is that any braking action that results from the stylus tracing through the record groove is small in proportion to the braking effect of the visuous oil. This would tend to keep the speed constant. As the motor fights the viscuous fluid and the resultant deccelarating forces on the platter in order to turn the platter at the correct speed, the braking effect of the stylus is a smaller proportion of the braking load than it would be without the viscuous fluid. Cheers, Thom ----- Original Message ----- From: phclark Sent: Saturday, February 19, 2000 10:29 PM Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? [ snip ] > > motor: he uses the rotational inertia of a massive platter, plus a > > constant-coupled brake system to ensure the variations in energy from the > > stylus into the platter is "swamped" by a high-energy system. This is where Verdier's characterization seemed implausible for a precision instrument. I envisioned your Ferrari flat out in first gear with the brakes on to make sure it never went over 20 mph. [ snip ] Peter C Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 10:28:36 -0700 From: Manfred Huber, Manfred Huber To: teres@aiko.com Sellek, Now you guys have me at exactly where I didn't want to be. The reason why I did not mention the SP article until now is that I also don't agree with much of it! There is way too much inertia and damping in a turntable for any motor to be able to react to varying forces resulting from stylus movement. No chance! And if there was such a motor then it would certainly be impossible to couple it to the platter by means of a piece of magnetic tape! There have to be other reasons for the sound differences between different kinds of motors. I'm no mechanical engineer but think about this: The turntable consists of two rotating masses (motor and platter) coupled by a string that adds compilance. There is no thing like a non-compliant link! What we do in using a heavy platter and an 'agile' motor is to separate the two time constants in this system as far as possible. This helps in reducing interaction. One might think that the inertia of the motor is already very much lower than that of the platter and that there is not much to be gained but it is not to be forgotten that the energy stored in a rotating mass rises with the rotational speed squared! Using a 1/2" pulley the rotational speed of the motor is about 24 times that of the platter. This means that you have to multiply the inertia of the motor by a factor of 24^2=576 before comparing it to the inertia of the platter. >I will be taking my Teres along the path suggested by Verdier in this particular regard. >That means the criteria become low-noise bearings and brushes, along with high linearity and >sufficient power for a high-energy environment (by turntable standards). IMHO this is a very reasonable approach and if you have a look at my motor selection you will notice that all these things where taken into consideration. Regards Manfred ------------------ Manfred Huber MHuber@t-online.de ------------------ Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 15:04:46 -0700 From: Anya & Fred Humphrey, Anya & Fred Humphrey To: teres@aiko.com ----- Original Message ----- From: "Manfred Huber" To: Sent: Sunday, February 20, 2000 11:26 AM Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Manfred and others, I can see that separating the motor and platter time constants widely might be a good thing. And for belt drive any connection will be fairly compliant. But in the case of rim drive and especially of direct drive, don't we approach a non-compliant situation? And if so, isn't there then the single time constant of the combined system? The claimed benefits are sharper transients and improved bass definition. The obvious drawback is that all motor imperfections-noise and speed variations-are directly coupled into the platter. Comments? Fred Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 15:05:47 -0700 From: Chris Brady, Chris Brady To: teres@aiko.com I can't resist weighing in on this discussion. Having done a lot of experimentation with a custom DAC I have first hand experience with the ill's of jitter in digital circuits. My initial bias was that it would be impossible to hear to effect of 10-50 picoseconds of jitter. Just too small to be significant. I was dead wrong. Jitter is a major issue in digital sound reproduction, implausible as it sounds. My first read of the SP motor article struck me the same as the discussion of digital jitter. The strength of a little motor is going to better regulate the rotational speed of a 35 pound platter? Nonsense! However, with further reading it dawned on me that minuscule speed variations of turntable rotational speed cause distortion that is probably similar to that caused by digital jitter. This kind of distortion is apparently far more audible than one might expect. So maybe the ridiculously small effect of the motor on rotational speed would actually be audible. It seems that using a high mass platter, viscous damping (drag) and motor selection / coupling are all methods for accomplishing the same objective, constant speed. I don't see any disagreement in what Verdier and Wilimzig are saying. They are just focusing on different methods for accomplishing the same thing. My take is that for a truly top notch table you have to effectively employ every available method to maintain constant speed. Intuitively it would seem that high mass alone would be sufficient. However, there seems to be ample evidence that this is not the case. Chris Manfred Huber wrote: > > Sellek, > > Now you guys have me at exactly where I didn't want to be. > The reason why I did not mention the SP article until now is > that I also don't agree with much of it! > > There is way too much inertia and damping in a turntable for any > motor to be able to react to varying forces resulting from stylus movement. > No chance! And if there was such a motor then it would certainly be impossible > to couple it to the platter by means of a piece of magnetic tape! > > There have to be other reasons for the sound differences between different kinds of motors. > I'm no mechanical engineer but think about this: The turntable consists of two rotating > masses (motor and platter) coupled by a string that adds compilance. There is > no thing like a non-compliant link! What we do in using a heavy platter and an 'agile' motor > is to separate the two time constants in this system as far as possible. This helps > in reducing interaction. One might think that the inertia of the motor is already very > much lower than that of the platter and that there is not much to be gained but it is not > to be forgotten that the energy stored in a rotating mass rises with the rotational > speed squared! Using a 1/2" pulley the rotational speed of the motor is about 24 times > that of the platter. This means that you have to multiply the inertia of the motor > by a factor of 24^2=576 before comparing it to the inertia of the platter. > > >I will be taking my Teres along the path suggested by Verdier in this particular regard. > >That means the criteria become low-noise bearings and brushes, along with high linearity and > >sufficient power for a high-energy environment (by turntable standards). > > IMHO this is a very reasonable approach and if you have a look at my motor selection you will > notice that all these things where taken into consideration. > > Regards > Manfred > > ------------------ > Manfred Huber > MHuber@t-online.de > ------------------ Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Sun, 20 Feb 2000 20:06:14 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: teres@aiko.com Thank you, Manfred. Your comment makes things clearer to me. Yesterday, Grant quoted a sentence from Verdier's (SP #11) response to Wilimzig's (SP #10) article. I think that the subsequent sentence and the following paragraph (not quoted) is helpful to those who still have "problems" with accepting the importance of a low inertia motor. >From Verdier's response in Sound Practices #11 (the part Grant previously quoted): "I must say that I don't think that low inertia in itself is that interesting of a quality for a turntable's motor. The next sentence and the subsequent paragraph (not quoted in the previous post): "It can even be a deficiency for players with relatively light platters, as indicated in my discussion of the value of mechanical braking below." "Another quality of the low inertia motor is much more interesting and relevant to the issue at hand: its rotation speed depends directly on the DC voltage. A simple integrated circuit regulator such as an LM 338 is enough to obtain perfect stability of the speed." So it seems as if low inertia motors also happen to be more responsive to DC voltage value. This would seem to be a good thing to me, as long as you had a good controller which we will. Cheers, Thom ----- Original Message ----- From: Manfred Huber To: Sent: Sunday, February 20, 2000 9:26 AM Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Sellek, Now you guys have me at exactly where I didn't want to be. The reason why I did not mention the SP article until now is that I also don't agree with much of it! There is way too much inertia and damping in a turntable for any motor to be able to react to varying forces resulting from stylus movement. No chance! And if there was such a motor then it would certainly be impossible to couple it to the platter by means of a piece of magnetic tape! There have to be other reasons for the sound differences between different kinds of motors. I'm no mechanical engineer but think about this: The turntable consists of two rotating masses (motor and platter) coupled by a string that adds compilance. There is no thing like a non-compliant link! What we do in using a heavy platter and an 'agile' motor is to separate the two time constants in this system as far as possible. This helps in reducing interaction. One might think that the inertia of the motor is already very much lower than that of the platter and that there is not much to be gained but it is not to be forgotten that the energy stored in a rotating mass rises with the rotational speed squared! Using a 1/2" pulley the rotational speed of the motor is about 24 times that of the platter. This means that you have to multiply the inertia of the motor by a factor of 24^2=576 before comparing it to the inertia of the platter. >I will be taking my Teres along the path suggested by Verdier in this particular regard. >That means the criteria become low-noise bearings and brushes, along with high linearity and >sufficient power for a high-energy environment (by turntable standards). IMHO this is a very reasonable approach and if you have a look at my motor selection you will notice that all these things where taken into consideration. Regards Manfred ------------------ Manfred Huber MHuber@t-online.de ------------------ Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Mon, 21 Feb 2000 09:12:52 -0700 From: Schei, Kenneth, Schei, Kenneth To: 'teres@aiko.com' Grant: Along with you, I don't really believe that the motor will ever be able to provide "instantaneous correction" to speed variations due to changing stylus drag, but the motors that we've been looking at are good choices for other reasons as well. Since I don't believe in instantaneous correction, I haven't abandoned the idea of using an elastic belt and letting the large inertia of the platter and the bearing drag (adjustable by varying viscosity) resist instantaneous changes, ala Verdier, and letting Manfred's excellent controller maintain the macro speed accuracy. The choices of motor and controller don't preclude either philosophy. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 > -----Original Message----- > From: Sellek, Grant (TSA) [SMTP:Grant.Sellek@transport.sa.gov.au] > Sent: Saturday, February 19, 2000 8:32 PM > To: 'teres@aiko.com' > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low > inertia?? > > > I suppose I missed a huge discussion of motors, although I have seen some > threads (I recall mention of "cogging" issues, for example). And I don't > know much about motors, so I cannot develop what I write below into a real > argument. But I must ask: > > Why are you using the criteria from Wilimzig's article in SP#10? When I > saw > Verdier's reply in SP#11, I decided that Wilimzig fell for a trap > described > in Joenet this week as "an internally consistent argument that does not > meet > the conditions of reality". > > Verdier wrote that low inertia is "not that interesting of a quality for a > turntable's motor". The fact that the Platine Verdier's motor is > low-inertia > is apparently not its main attribute. He also wrote that if Wilimzig's > assumption were true, (that it is the motor's job to instantaneously > correct > platter speed variations caused by the action of the stylus in the > groove), > then no turntable could work well, because no motor is good enough. > > Verdier's solution to this issue has, it seems to me, nothing to do with > the > motor: he uses the rotational inertia of a massive platter, plus a > constant-coupled brake system to ensure the variations in energy from the > stylus into the platter is "swamped" by a high-energy system. > > I don't believe that these tiny motors will have any useful "instantaneous > correction" effect in a high-energy system, such as the Teres platter and > bearing with viscous oil. You would have to greatly lower the energy of > the > system to let the motor try its luck. I will be taking my Teres along the > path suggested by Verdier in this particular regard. That means the > criteria > become low-noise bearings and brushes, along with high linearity and > sufficient power for a high-energy environment (by turntable standards). > > OK, shred me. I honestly don't know much about electric motors. > Grant > > > Grant Sellek > Adelaide, Australia > grant.sellek@transport.sa.gov.au > > > -----Original Message----- > From: Chris Brady [mailto:cbrady@sgi.com] > Sent: Sunday, 20 February 2000 3:30 AM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" > > > I received the Maxxon catalogue yesterday and have been researching other > motor possibilities. Using the criteria from the SP "Turn Your Table" > article I came up with 7 candidates. I called for a price for each of > the motors, but have not heard back yet. Here's a list of the motors > and their specs. > > Pgm Part# MI STG rpm/V RadF Watts > ===================================================================== > RE-Stk 118690 1.15 414 304 1.5 3.2 > RE-Std 118691 1.10 432 217 1.5 3.2 > RE-Stk 118746 10.3 37.5 218 16.0 10.0 > > S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 > S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 > > AX-Stk 110189 11.8 103 180 5.5 7.0 > AX-Stk 110212 11.8 103 180 5.5 4.5 > > Legend: > Pgm This is a motor series. RE is the top of the line and > uses Neodymium magnets. The S series is next to the > top and uses Alnico magnets. AX is for the A-Max series > and is the same as the S series in a more economical > package. > > MI Moment of inertia. Less is better and the SP article > suggested values less than 10. > > STG Speed/torque gradient. This is an indication of the motors > power. It is a measure of the motors ability to maintain > constant speed with load variations. Less is better and the > SP article suggested values of less than 1000 and implied > that less than 500 is needed for heavier platters. > > rpm/V RPM per volt. Values of 150 to 300 work well. > > RadF Allowable radial force. > > Part number 110189 is what Manfred suggested. It's moment of intertial is > on the high side, but it is quite powerful. The 110212 has the same specs > but a lower power rating and may be less expensive. > > Part number 2326-942-12-111-050 is the motor recommended in the SP > article. > It has a different intertia/power balance that may be better for our > moderately heavy platter. > > The RE 118746 is really impressive. Lower inertia than the 110189 and 3 > times as powerful! This is probably very pricy. > > The RE 118690 and 118691 motors are a little weak but the moment of > inertia is remarkably low. > > The RE series motors are clearly the best, but the prices may be > prohibitive. > I don't know which of the two would offer the best inertia/power > compromise. > > I'll send out the pricing info when I get it. > > Chris Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Mon, 21 Feb 2000 09:14:32 -0700 From: Schei, Kenneth, Schei, Kenneth To: 'teres@aiko.com' Well said, Roscoe. Ken > -----Original Message----- > From: Roscoe Primrose [SMTP:roscoe@aiko.com] > Sent: Saturday, February 19, 2000 11:41 PM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low > inertia?? > > "Sellek, Grant (TSA)" wrote: > > > > I suppose I missed a huge discussion of motors, although I have seen > some > > threads (I recall mention of "cogging" issues, for example). And I don't > > know much about motors, so I cannot develop what I write below into a > real > > argument. But I must ask: > > > > Why are you using the criteria from Wilimzig's article in SP#10? When I > saw > > Verdier's reply in SP#11, I decided that Wilimzig fell for a trap > described > > in Joenet this week as "an internally consistent argument that does not > meet > > the conditions of reality". > > I too thought Wilimzig was wrong in some of his logic.. Since the > motor's rotation and the platters rotation are locked together (ideally, > and nearly so with something that doesn't stretch) having a motor with > low intertia with a heavy platter is a lot like having a diet soda with > a pound of butter, it doesn't make a rats ass of difference, it's the > intertia of the whole rotating system that matters. > > > > > Verdier wrote that low inertia is "not that interesting of a quality for > a > > turntable's motor". The fact that the Platine Verdier's motor is > low-inertia > > is apparently not its main attribute. He also wrote that if Wilimzig's > > assumption were true, (that it is the motor's job to instantaneously > correct > > platter speed variations caused by the action of the stylus in the > groove), > > then no turntable could work well, because no motor is good enough. > > Indeed, unless the whole rotating system has inertia approaching zero... > > > OK, shred me. I honestly don't know much about electric motors. > > Grant > > > > Maybe not, but your physics doesn't seem lacking. > > Peace > -- > Roscoe Primrose > -- mailto:roscoe@aiko.com -- http://www.aiko.com/roscoe -- > > "Once in a while you get shown the light > In the strangest of places if you look at it right." Robert Hunter Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Mon, 21 Feb 2000 09:17:23 -0700 From: Schei, Kenneth, Schei, Kenneth To: 'teres@aiko.com' Thom: You're not confused at all. I think you see the situation very clearly. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 > -----Original Message----- > From: Thom Mackris / Joan Panzella [SMTP:tmackris@earthlink.net] > Sent: Sunday, February 20, 2000 12:28 AM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low > inertia?? > > Grant, > > I don't think you missed much on motors, and you have thought this issue > out > well. I personally don't have a strong enough grasp of the physics and so > I > find myself waffling on the issue of low inertia motors. With a > non-compliant belt (recording tape), it seems as if the platter and the > motor are intimately tied to each other and that the only inertia to be > considered is the combined inertia of the system of motor & platter. What > am I missing here? > > What really confuses me about this whole issue are the reports of > differences between two competent drive systems (motor + controller) as > well > as between choices of belt material on a 'table like a Verdier. > Intuitively, I would think that changes to these parts would not result in > audible differences. I would expect that the mass of the platter on the > Verdier along with the viscuous braking would control and regulate the > speed > of the platter. Reports are that mass and braking are not enough, and > that > the motor and controller must be designed to a very high standard. Are > these reports merely those of proud designers who are emotionally wed to > their improvements? All of us are vulnerable to this effect - "I > struggled > to make this change/tweek, it's different, therefor I made an > improvement". > > I agree with Verdier's comments that a motor cannot react to instantaneous > speed variations in the platter. The reaction would be much too late and > would just smear the signal. I rather see that the only thing that a > motor > can do is to resist these variations in the first place through a stable > power supply along with having enough torque to do the job and a > non-compliant belt. > > As a footnote, early in the bearing dialog we spoke of viscuous damping > and > designed the well in the center of the bearing specifically for this > purpose. Originally, we were just looking to reduce the bearing contact > area (less noise) but as we got into it, we expanded this well as much as > financially possible in order to effect damping. There was a limit to how > big the well could get based on (a) not wanting to leave too thin a wall > on > the bearing and (b) the price of the next size of brass stock sending the > project financially out of control. > > Confused in Denver (but confident in Manfred) ... > Thom > > ----- Original Message ----- > From: Sellek, Grant (TSA) > To: > Sent: Saturday, February 19, 2000 8:32 PM > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? > > > I suppose I missed a huge discussion of motors, although I have seen some > threads (I recall mention of "cogging" issues, for example). And I don't > know much about motors, so I cannot develop what I write below into a real > argument. But I must ask: > > Why are you using the criteria from Wilimzig's article in SP#10? When I > saw > Verdier's reply in SP#11, I decided that Wilimzig fell for a trap > described > in Joenet this week as "an internally consistent argument that does not > meet > the conditions of reality". > > Verdier wrote that low inertia is "not that interesting of a quality for a > turntable's motor". The fact that the Platine Verdier's motor is > low-inertia > is apparently not its main attribute. He also wrote that if Wilimzig's > assumption were true, (that it is the motor's job to instantaneously > correct > platter speed variations caused by the action of the stylus in the > groove), > then no turntable could work well, because no motor is good enough. > > Verdier's solution to this issue has, it seems to me, nothing to do with > the > motor: he uses the rotational inertia of a massive platter, plus a > constant-coupled brake system to ensure the variations in energy from the > stylus into the platter is "swamped" by a high-energy system. > > I don't believe that these tiny motors will have any useful "instantaneous > correction" effect in a high-energy system, such as the Teres platter and > bearing with viscous oil. You would have to greatly lower the energy of > the > system to let the motor try its luck. I will be taking my Teres along the > path suggested by Verdier in this particular regard. That means the > criteria > become low-noise bearings and brushes, along with high linearity and > sufficient power for a high-energy environment (by turntable standards). > > OK, shred me. I honestly don't know much about electric motors. > Grant > > > Grant Sellek > Adelaide, Australia > grant.sellek@transport.sa.gov.au > > > -----Original Message----- > From: Chris Brady [mailto:cbrady@sgi.com] > Sent: Sunday, 20 February 2000 3:30 AM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" > > > I received the Maxxon catalogue yesterday and have been researching other > motor possibilities. Using the criteria from the SP "Turn Your Table" > article I came up with 7 candidates. I called for a price for each of > the motors, but have not heard back yet. Here's a list of the motors > and their specs. > > Pgm Part# MI STG rpm/V RadF Watts > ===================================================================== > RE-Stk 118690 1.15 414 304 1.5 3.2 > RE-Std 118691 1.10 432 217 1.5 3.2 > RE-Stk 118746 10.3 37.5 218 16.0 10.0 > > S-Std 2522-941-12-112-000 3.47 495 199 2.8 3.8 > S-Stk 2326-942-12-111-050 7.77 206 203 4.3 4.0 > > AX-Stk 110189 11.8 103 180 5.5 7.0 > AX-Stk 110212 11.8 103 180 5.5 4.5 > > Legend: > Pgm This is a motor series. RE is the top of the line and > uses Neodymium magnets. The S series is next to the > top and uses Alnico magnets. AX is for the A-Max series > and is the same as the S series in a more economical > package. > > MI Moment of inertia. Less is better and the SP article > suggested values less than 10. > > STG Speed/torque gradient. This is an indication of the motors > power. It is a measure of the motors ability to maintain > constant speed with load variations. Less is better and the > SP article suggested values of less than 1000 and implied > that less than 500 is needed for heavier platters. > > rpm/V RPM per volt. Values of 150 to 300 work well. > > RadF Allowable radial force. > > Part number 110189 is what Manfred suggested. It's moment of intertial is > on the high side, but it is quite powerful. The 110212 has the same specs > but a lower power rating and may be less expensive. > > Part number 2326-942-12-111-050 is the motor recommended in the SP > article. > It has a different intertia/power balance that may be better for our > moderately heavy platter. > > The RE 118746 is really impressive. Lower inertia than the 110189 and 3 > times as powerful! This is probably very pricy. > > The RE 118690 and 118691 motors are a little weak but the moment of > inertia is remarkably low. > > The RE series motors are clearly the best, but the prices may be > prohibitive. > I don't know which of the two would offer the best inertia/power > compromise. > > I'll send out the pricing info when I get it. > > Chris > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Mon, 21 Feb 2000 09:22:23 -0700 From: Schei, Kenneth, Schei, Kenneth To: 'teres@aiko.com' Manfred: Thanks for an excellent analysis. I heartily endorse your choices of motor and controller. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 > -----Original Message----- > From: MHuber@t-online.de [SMTP:MHuber@t-online.de] > Sent: Sunday, February 20, 2000 9:27 AM > To: teres@aiko.com > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low > inertia?? > > Sellek, > > Now you guys have me at exactly where I didn't want to be. > The reason why I did not mention the SP article until now is > that I also don't agree with much of it! > > There is way too much inertia and damping in a turntable for any > motor to be able to react to varying forces resulting from stylus > movement. > No chance! And if there was such a motor then it would certainly be > impossible > to couple it to the platter by means of a piece of magnetic tape! > > There have to be other reasons for the sound differences between different > kinds of motors. > I'm no mechanical engineer but think about this: The turntable consists of > two rotating > masses (motor and platter) coupled by a string that adds compilance. There > is > no thing like a non-compliant link! What we do in using a heavy platter > and an 'agile' motor > is to separate the two time constants in this system as far as possible. > This helps > in reducing interaction. One might think that the inertia of the motor is > already very > much lower than that of the platter and that there is not much to be > gained but it is not > to be forgotten that the energy stored in a rotating mass rises with the > rotational > speed squared! Using a 1/2" pulley the rotational speed of the motor is > about 24 times > that of the platter. This means that you have to multiply the inertia of > the motor > by a factor of 24^2=576 before comparing it to the inertia of the platter. > > >I will be taking my Teres along the path suggested by Verdier in this > particular regard. > >That means the criteria become low-noise bearings and brushes, along with > high linearity and > >sufficient power for a high-energy environment (by turntable standards). > > IMHO this is a very reasonable approach and if you have a look at my motor > selection you will > notice that all these things where taken into consideration. > > Regards > Manfred > > > > > > > > > ------------------ > Manfred Huber > MHuber@t-online.de > ------------------ > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Mon, 21 Feb 2000 20:42:32 -0700 From: Sellek, Grant (TSA), Sellek, Grant (TSA) To: 'teres@aiko.com' Chris, it is hard to argue when you say "employ every available method to maintain constant speed". Such a catch-all approach is sure to succeed, and is at the core of all the extreme audio fringe (core of the fringe?) stuff that Teres is part of. The question is always, "is there a tradeoff?". We could take the same approach (every available method) to every performance issue. You want low noise? Air bearings, then, because we never know what metal and oil will add to noise. And the deck had better be in an acoustically isolated chamber (along with all your valve amps, Chris) to avoid microphonic noise. Every available method, remember. The issue here is: are there any tradeoffs in focusing on low inertia motors, or is it a "freebie" that has no downside except a few extra dollars? If that's the case, I'm all for it. But I question it being a prime selection criterion for the motor; perhaps it could be a secondary criterion to differentiate between motors that equally meet the prime criteria. Then I am all in favour. So what are the prime criteria, that all the motors listed by Manfred meet equally, and presumably do better at than any other motor or motor type? I want to know the prime criteria. Are they power (minimum = ?), bearing noise, brush noise, and "cogging"? If so, why not eliminate brushes? Is there a tradeoff? etc etc. Grant -----Original Message----- From: Chris Brady [mailto:cbrady@sgi.com] Sent: Monday, 21 February 2000 7:35 am I can't resist weighing in on this discussion. Having done a lot of experimentation with a custom DAC I have first hand experience with the ill's of jitter in digital circuits. My initial bias was that it would be impossible to hear to effect of 10-50 picoseconds of jitter. Just too small to be significant. I was dead wrong. Jitter is a major issue in digital sound reproduction, implausible as it sounds. My first read of the SP motor article struck me the same as the discussion of digital jitter. The strength of a little motor is going to better regulate the rotational speed of a 35 pound platter? Nonsense! However, with further reading it dawned on me that minuscule speed variations of turntable rotational speed cause distortion that is probably similar to that caused by digital jitter. This kind of distortion is apparently far more audible than one might expect. So maybe the ridiculously small effect of the motor on rotational speed would actually be audible. It seems that using a high mass platter, viscous damping (drag) and motor selection / coupling are all methods for accomplishing the same objective, constant speed. I don't see any disagreement in what Verdier and Wilimzig are saying. They are just focusing on different methods for accomplishing the same thing. My take is that for a truly top notch table you have to effectively employ every available method to maintain constant speed. Intuitively it would seem that high mass alone would be sufficient. However, there seems to be ample evidence that this is not the case. Chris Manfred Huber wrote: > > Sellek, > > Now you guys have me at exactly where I didn't want to be. > The reason why I did not mention the SP article until now is > that I also don't agree with much of it! > > There is way too much inertia and damping in a turntable for any > motor to be able to react to varying forces resulting from stylus movement. > No chance! And if there was such a motor then it would certainly be impossible > to couple it to the platter by means of a piece of magnetic tape! > > There have to be other reasons for the sound differences between different kinds of motors. > I'm no mechanical engineer but think about this: The turntable consists of two rotating > masses (motor and platter) coupled by a string that adds compilance. There is > no thing like a non-compliant link! What we do in using a heavy platter and an 'agile' motor > is to separate the two time constants in this system as far as possible. This helps > in reducing interaction. One might think that the inertia of the motor is already very > much lower than that of the platter and that there is not much to be gained but it is not > to be forgotten that the energy stored in a rotating mass rises with the rotational > speed squared! Using a 1/2" pulley the rotational speed of the motor is about 24 times > that of the platter. This means that you have to multiply the inertia of the motor > by a factor of 24^2=576 before comparing it to the inertia of the platter. > > >I will be taking my Teres along the path suggested by Verdier in this particular regard. > >That means the criteria become low-noise bearings and brushes, along with high linearity and > >sufficient power for a high-energy environment (by turntable standards). > > IMHO this is a very reasonable approach and if you have a look at my motor selection you will > notice that all these things where taken into consideration. > > Regards > Manfred > > ------------------ > Manfred Huber > MHuber@t-online.de > ------------------ Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Mon, 21 Feb 2000 21:04:27 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: teres@aiko.com I'm really treading in an area where I know very little, Grant. When have I let this stop me :-) I think Manfred's point about separating the time constants of the platter and motor by as much as possible was an interesting one, especially the point about the moment of inertia being proportional to the square of the speed (the motor will be rotating 24 times faster than the platter if the pulley is .5" diameter). Verdier's comment about low inertia motors being more responsive to changes in DC voltage were also provocative. Audible difference? Worth the marginal price increase? Beats me, but we certainly have the advantage of Manfred having "broken trail" for us. Perhaps someone else is in a better position to comment than I am. Cheers, Thom ----- Original Message ----- From: Sellek, Grant (TSA) To: Sent: Monday, February 21, 2000 7:40 PM Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Chris, it is hard to argue when you say "employ every available method to maintain constant speed". Such a catch-all approach is sure to succeed, and is at the core of all the extreme audio fringe (core of the fringe?) stuff that Teres is part of. The question is always, "is there a tradeoff?". We could take the same approach (every available method) to every performance issue. You want low noise? Air bearings, then, because we never know what metal and oil will add to noise. And the deck had better be in an acoustically isolated chamber (along with all your valve amps, Chris) to avoid microphonic noise. Every available method, remember. The issue here is: are there any tradeoffs in focusing on low inertia motors, or is it a "freebie" that has no downside except a few extra dollars? If that's the case, I'm all for it. But I question it being a prime selection criterion for the motor; perhaps it could be a secondary criterion to differentiate between motors that equally meet the prime criteria. Then I am all in favour. So what are the prime criteria, that all the motors listed by Manfred meet equally, and presumably do better at than any other motor or motor type? I want to know the prime criteria. Are they power (minimum = ?), bearing noise, brush noise, and "cogging"? If so, why not eliminate brushes? Is there a tradeoff? etc etc. Grant -----Original Message----- From: Chris Brady [mailto:cbrady@sgi.com] Sent: Monday, 21 February 2000 7:35 am I can't resist weighing in on this discussion. Having done a lot of experimentation with a custom DAC I have first hand experience with the ill's of jitter in digital circuits. My initial bias was that it would be impossible to hear to effect of 10-50 picoseconds of jitter. Just too small to be significant. I was dead wrong. Jitter is a major issue in digital sound reproduction, implausible as it sounds. My first read of the SP motor article struck me the same as the discussion of digital jitter. The strength of a little motor is going to better regulate the rotational speed of a 35 pound platter? Nonsense! However, with further reading it dawned on me that minuscule speed variations of turntable rotational speed cause distortion that is probably similar to that caused by digital jitter. This kind of distortion is apparently far more audible than one might expect. So maybe the ridiculously small effect of the motor on rotational speed would actually be audible. It seems that using a high mass platter, viscous damping (drag) and motor selection / coupling are all methods for accomplishing the same objective, constant speed. I don't see any disagreement in what Verdier and Wilimzig are saying. They are just focusing on different methods for accomplishing the same thing. My take is that for a truly top notch table you have to effectively employ every available method to maintain constant speed. Intuitively it would seem that high mass alone would be sufficient. However, there seems to be ample evidence that this is not the case. Chris Manfred Huber wrote: > > Sellek, > > Now you guys have me at exactly where I didn't want to be. > The reason why I did not mention the SP article until now is > that I also don't agree with much of it! > > There is way too much inertia and damping in a turntable for any > motor to be able to react to varying forces resulting from stylus movement. > No chance! And if there was such a motor then it would certainly be impossible > to couple it to the platter by means of a piece of magnetic tape! > > There have to be other reasons for the sound differences between different kinds of motors. > I'm no mechanical engineer but think about this: The turntable consists of two rotating > masses (motor and platter) coupled by a string that adds compilance. There is > no thing like a non-compliant link! What we do in using a heavy platter and an 'agile' motor > is to separate the two time constants in this system as far as possible. This helps > in reducing interaction. One might think that the inertia of the motor is already very > much lower than that of the platter and that there is not much to be gained but it is not > to be forgotten that the energy stored in a rotating mass rises with the rotational > speed squared! Using a 1/2" pulley the rotational speed of the motor is about 24 times > that of the platter. This means that you have to multiply the inertia of the motor > by a factor of 24^2=576 before comparing it to the inertia of the platter. > > >I will be taking my Teres along the path suggested by Verdier in this particular regard. > >That means the criteria become low-noise bearings and brushes, along with high linearity and > >sufficient power for a high-energy environment (by turntable standards). > > IMHO this is a very reasonable approach and if you have a look at my motor selection you will > notice that all these things where taken into consideration. > > Regards > Manfred > > ------------------ > Manfred Huber > MHuber@t-online.de > ------------------ Subject: [teres] synchronous vs. asynchronous motors Date: Tue, 22 Feb 2000 06:26:40 -0700 From: Manfred Huber, Manfred Huber To: teres@aiko.com Hello Group, I have done some mathematical analysis of the mechanical system made up from a motor and a rotating mass and found some interesting (surprising to me) results: sync (ac) motor: ---------------- The system made up from a synchronous motor and the platter is able to oscillate! Wether oscillation occurs depends on the strength of the motor, the moving mass and the amount of frictional force (damping) The best you can achieve with a sync. motor is aperiodic damping. This is because in a sync motor the torque linearly depends on the angle in between the two magnetic fields in the motor. One field is generated by the applied electrical power. It is rotating at a fixed speed dictated by the frequency of the power supply. The rotor has permanent magnets that generate a static field. For the motor to work properly the rotor has to rotate at the same speed as the stator field. The whole thing behaves exactly like a PLL (phase locked loop) Imagine the platter is too slow and the rotor falls behind the stator field. Now the motor tries to get the angle in between the fields back to its static value. As the stator field move on at a fixed speed the rotor has to move at a speed higher than that of the stator field. This means that there has to be some speed overshot no matter how much damping we have in the system! The damping can be influenced by to amount of voltage that is applied to the motor. The best case is reached when the voltage is just sufficient to generate enough torque to keep the platter going. In this case we have aperiodic damping. In practice we need to apply a higher voltage in order to avoid the motor falling out of sync when the system is disturbed. This means that the speed will always ring when recovering from a disturbance. async (dc) motor: ----------------- The system made up from an async motor and platter is a first order system, it has no resonance i.e. there is no oscillation possible no matter how strong the motor, how heavy the platter and how much damping is involved! This is because the torque linearly depends on the angular velocity. Imagine the platter is too slow and the motor generates more torque in order to bring the speed up. As the speed of the platter rises the torque decreases thus lowering the angular acceleration. The speed will 'creep' asymptotically to it's end point. There is no possibility for oscillaton. Not even a single overshot. Note that I do not say that damping does not matter when using an async motor. I used a very simple model that did not include the following points: - interaction of platter and needle - elastic coupling of platter and motor - ripple of torque generated by commutation I hope I managed to describe what's going on. Any takers? Regards Manfred ------------------ Manfred Huber MHuber@t-online.de ------------------ Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? Date: Tue, 22 Feb 2000 08:34:29 -0700 From: Schei, Kenneth, Schei, Kenneth To: 'teres@aiko.com' I'm not sure why the fast response of a low-inertia motor is of importance to us when we are deliberately designing our motor controller to have a low response frequency to prevent audible "hunting." Am I missing something here? Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 > -----Original Message----- > From: Thom Mackris / Joan Panzella [SMTP:tmackris@earthlink.net] > Sent: Monday, February 21, 2000 8:10 PM > To: teres@aiko.com > Subject: Re: [teres] Motor/pulley/controller/supply "kit" - low > inertia?? > > I'm really treading in an area where I know very little, Grant. When have > I > let this stop me :-) > > I think Manfred's point about separating the time constants of the platter > and motor by as much as possible was an interesting one, especially the > point about the moment of inertia being proportional to the square of the > speed (the motor will be rotating 24 times faster than the platter if the > pulley is .5" diameter). > > Verdier's comment about low inertia motors being more responsive to > changes > in DC voltage were also provocative. > > Audible difference? Worth the marginal price increase? Beats me, but we > certainly have the advantage of Manfred having "broken trail" for us. > Perhaps someone else is in a better position to comment than I am. > > Cheers, > Thom > > ----- Original Message ----- > From: Sellek, Grant (TSA) > To: > Sent: Monday, February 21, 2000 7:40 PM > Subject: RE: [teres] Motor/pulley/controller/supply "kit" - low inertia?? > > > Chris, it is hard to argue when you say "employ every available method to > maintain constant speed". Such a catch-all approach is sure to succeed, > and > is at the core of all the extreme audio fringe (core of the fringe?) stuff > that Teres is part of. The question is always, "is there a tradeoff?". We > could take the same approach (every available method) to every performance > issue. > > You want low noise? Air bearings, then, because we never know what metal > and > oil will add to noise. And the deck had better be in an acoustically > isolated chamber (along with all your valve amps, Chris) to avoid > microphonic noise. Every available method, remember. > > The issue here is: are there any tradeoffs in focusing on low inertia > motors, or is it a "freebie" that has no downside except a few extra > dollars? If that's the case, I'm all for it. But I question it being a > prime > selection criterion for the motor; perhaps it could be a secondary > criterion > to differentiate between motors that equally meet the prime criteria. Then > I > am all in favour. > > So what are the prime criteria, that all the motors listed by Manfred meet > equally, and presumably do better at than any other motor or motor type? I > want to know the prime criteria. > > Are they power (minimum = ?), bearing noise, brush noise, and "cogging"? > If > so, why not eliminate brushes? Is there a tradeoff? etc etc. > > Grant > > -----Original Message----- > From: Chris Brady [mailto:cbrady@sgi.com] > Sent: Monday, 21 February 2000 7:35 am > > I can't resist weighing in on this discussion. Having done a lot of > experimentation with a custom DAC I have first hand experience with > the ill's of jitter in digital circuits. My initial bias was that it > would be impossible to hear to effect of 10-50 picoseconds of jitter. > Just too small to be significant. I was dead wrong. Jitter is a major > issue in digital sound reproduction, implausible as it sounds. > > My first read of the SP motor article struck me the same as the discussion > of digital jitter. The strength of a little motor is going to better > regulate the rotational speed of a 35 pound platter? Nonsense! > However, with further reading it dawned on me that minuscule speed > variations > of turntable rotational speed cause distortion that is probably similar to > that caused by digital jitter. This kind of distortion is apparently far > more audible than one might expect. So maybe the ridiculously small > effect of the motor on rotational speed would actually be audible. > > It seems that using a high mass platter, viscous damping (drag) and > motor selection / coupling are all methods for accomplishing the same > objective, constant speed. I don't see any disagreement in what Verdier > and Wilimzig are saying. They are just focusing on different methods > for accomplishing the same thing. My take is that for a truly top notch > table you have to effectively employ every available method to maintain > constant speed. Intuitively it would seem that high mass alone would be > sufficient. However, there seems to be ample evidence that this is not > the case. > > Chris > > Manfred Huber wrote: > > > > Sellek, > > > > Now you guys have me at exactly where I didn't want to be. > > The reason why I did not mention the SP article until now is > > that I also don't agree with much of it! > > > > There is way too much inertia and damping in a turntable for any > > motor to be able to react to varying forces resulting from stylus > movement. > > No chance! And if there was such a motor then it would certainly be > impossible > > to couple it to the platter by means of a piece of magnetic tape! > > > > There have to be other reasons for the sound differences between > different > kinds of motors. > > I'm no mechanical engineer but think about this: The turntable consists > of > two rotating > > masses (motor and platter) coupled by a string that adds compilance. > There > is > > no thing like a non-compliant link! What we do in using a heavy platter > and an 'agile' motor > > is to separate the two time constants in this system as far as possible. > This helps > > in reducing interaction. One might think that the inertia of the motor > is > already very > > much lower than that of the platter and that there is not much to be > gained but it is not > > to be forgotten that the energy stored in a rotating mass rises with the > rotational > > speed squared! Using a 1/2" pulley the rotational speed of the motor is > about 24 times > > that of the platter. This means that you have to multiply the inertia of > the motor > > by a factor of 24^2=576 before comparing it to the inertia of the > platter. > > > > >I will be taking my Teres along the path suggested by Verdier in this > particular regard. > > >That means the criteria become low-noise bearings and brushes, along > with > high linearity and > > >sufficient power for a high-energy environment (by turntable > standards). > > > > IMHO this is a very reasonable approach and if you have a look at my > motor > selection you will > > notice that all these things where taken into consideration. > > > > Regards > > Manfred > > > > ------------------ > > Manfred Huber > > MHuber@t-online.de > > ------------------ > Subject: Re: [teres] synchronous vs. asynchronous motors Date: Tue, 22 Feb 2000 14:47:30 -0700 From: Steve Zettel, Steve Zettel To: teres@aiko.com on 2/22/00 05:23, Manfred Huber at MHuber@t-online.de wrote: > Hello Group, > > I have done some mathematical analysis of the mechanical system made up from a > motor and a rotating mass and found some interesting (surprising to me) > results: > > sync (ac) motor: ---------------- > > The system made up from a synchronous motor and the platter is able to > oscillate! Wether oscillation occurs depends on the strength of the motor, the > moving mass and the amount of frictional force (damping) The best you can > achieve with a sync. motor is aperiodic damping. This is because in a sync > motor the torque linearly depends on the angle in between the two magnetic > fields in the motor. One field is generated by the applied electrical power. > It is rotating at a fixed speed dictated by the frequency of the power supply. > The rotor has permanent magnets that generate a static field. For the motor to > work properly the rotor has to rotate at the same speed as the stator field. > The whole thing behaves exactly like a PLL (phase locked loop) > > Imagine the platter is too slow and the rotor falls behind the stator field. > Now the motor tries to get the angle in between the fields back to its static > value. As the stator field move on at a fixed speed the rotor has to move at a > speed higher than that of the stator field. This means that there has to be > some speed overshot no matter how much damping we have in the system! > > The damping can be influenced by to amount of voltage that is applied to the > motor. The best case is reached when the voltage is just sufficient to > generate enough torque to keep the platter going. In this case we have > aperiodic damping. In practice we need to apply a higher voltage in order to > avoid the motor falling out of sync when the system is disturbed. This means > that the speed will always ring when recovering from a disturbance. > > async (dc) motor: ----------------- > > The system made up from an async motor and platter is a first order system, it > has no resonance i.e. there is no oscillation possible no matter how strong > the motor, how heavy the platter and how much damping is involved! > > This is because the torque linearly depends on the angular velocity. Imagine > the platter is too slow and the motor generates more torque in order to bring > the speed up. As the speed of the platter rises the torque decreases thus > lowering the angular acceleration. The speed will 'creep' asymptotically to > it's end point. There is no possibility for oscillaton. Not even a single > overshot. > > Note that I do not say that damping does not matter when using an async motor. > I used a very simple model that did not include the following points: > > - interaction of platter and needle - elastic coupling of platter and motor - > ripple of torque generated by commutation > > I hope I managed to describe what's going on. > > Any takers? > > Regards Manfred Interesting analysis, Manfred. I have never done the math, but I have had some pragmatic experience with sound (vibrational) analysis of both AC and DC motors in nuclear submarines and nuclear propulsion plants on surface ships, as well as a background teaching electrical theory and operations to Navy nuclear propulsion candidates. In both cases, the magnetic coupling between stator and rotor is a resilent link. As you so correctly point out, the synchronous AC motor is subject to overshoot and "ringing" or oscillation in response to speed or load variations, while the DC motor is relatively immune from these effects unless a load is instantaneously removed (unusual, and not applicable in our turntable application), In vibration or sound analysis, this "resonance" can often be seen with the AC synchronous motor at certain states of load and speed -- and of course, these are avoided at all costs for submarine uses! Interestingly, the AC induction motor shares many of the desirable qualities of the DC motor in terms of immunity from overshoot, and it's reliance on angular velocity or relative motion to generate the rotor's magnetic field. Under load an AC induction motor always runs slightly slower than the rotating magnetic field of the stator, represented as a certain percentage slip. Starting torque is is quite high (as is starting current) with this type of AC motor, and torque also increases as the rotor is loaded more and more (and speed droops towards eventual stall). Unfortunately, I am unaware of any small, precision AC induction motors on the scale needed for our project. I am quite comfortable with our choice of a DC motor for our turntable for these reasons, and others discussed before. It would be enlightening to determine which of the many parameters of DC motors are most critical for our turntable application. My gut feel is that while low inertia may not be the most important factor, it is still very important as Manfred has explained to keep it as low as possible to separate the motors moment of inertia from that of the platter. Best regards, Steve Z near Libby, MT USA Subject: Re: [teres] Motor & Controller Date: Tue, 22 Feb 2000 19:47:26 -0700 From: Thom Mackris / Joan Panzella, Thom Mackris / Joan Panzella To: teres@aiko.com Fritz, If I recall correctly, Manfred estimated the parts cost to be around $50.00. Add to this about $18.00 for the circuit board, perhaps a switch. We'll probably be building the case ourselves, but let's be generous and allocate $20.00 for parts. So, assuming $60.00 for the motor, $150-$160 seems like a safe guess ... for a superb power supply. Thom ----- Original Message ----- From: Fritz Moore To: Sent: Tuesday, February 22, 2000 1:10 PM Subject: RE: [teres] RB250 [tonearm talk snipped] Was there ever a ball park price put out on the motor controller? I remember the motor itself at about $60.00 US? Fritz Subject: belt material, was RE: [teres] synchronous vs. asynchronous motors; Date: Tue, 22 Feb 2000 21:59:15 -0700 From: Sellek, Grant (TSA), Sellek, Grant (TSA) To: 'teres@aiko.com' -----Original Message----- From: phclark [mailto:phclark@uswest.net] Subject: Re: [teres] synchronous vs. asynchronous motors 2. Elastic coupling is inevitable at some level. Non-compliant materials like magnetic tape would seem to be preferable to, say, string. =============================================================== Peter, I'm not entirely convinced about this, especially if we concede that the motor is not providing effective instantaneous speed correction. I would agree with the advantage of non-compliant materials if there were no tradeoffs, however I reckon the danger of a mag tape drive is that it will efficiently transmit any motor noise to the platter, either bearing-type or brush-type noise. We are trying to reduce that noise at its source with a good choice of motor, but that doesn't mean we can ignore the tranmission of noise through the drivetrain. Like Chris Brady said, take every possible measure. I don't want an elastic coupling either. Who wants the platter going boing boing on the end of a rubber band? I think this is what Peter and others who favour mag tape are trying to avoid. So I am in favour of a stiff but lossy drivetrain. Mag tape is stiff but not lossy. Rubber is slightly lossy but not stiff. The best candidate that comes to mind is string, or cotton thread! Does anyone have a better suggestion for a stiff, lossy material? What about leather? Grant Grant Sellek Adelaide, Australia grant.sellek@transport.sa.gov.au