[Editor's note: Items disussed in the Subchassis topic include the subchassis, armboard and suspension. There are generally two schools of thought being expressed in the dialogs to date: (a) a subchassis that sits in a sandbox which rests on an air bladder and (b) A more conventional high mass design like the Scheu or Verdier ] ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Thursday, December 16, 1999 11:42 PM Subject: Scheu-Subchassis Bearing - accomodate a removable bearing? We'll need to watch the bearing design unfold. Armboard: A removable armboard made out of either acrylic, or perhaps a sandwich of acrylic & lead sheet seem to allow great flexibility. We're thinking that with enough bolts holding it down & it being of the same material as the subchassis that this gets us close to George Merrill's ideal of a one piece subchassis/armboard with the increased flexibility in the event of needing to re-drill for another tonearm. If we have a machinist drill our subchassis (armboard mounting holes) and corresponding armboards (perhaps aspare for each of us), we can have interchangable arms (more or less). I could bring my Audiocraft arm to Chris & he could evaluate it in his systemrelatively easily. How to route the tonearm cable: I know Igor is thinking of hard wiring the tonearm cable to his phono stage. Additionally, all of our visions of our subchassis' is bound to differ a bit, if only for aesthetic reasons. For example, I'm toying with the idea of having the subchassis forming the top plate of a sandbox like the BrightStar. This would make routing the tonearm cable out the bottom a bit of a challenge. Alternately, I've thought of having the subchassis sit on top of a Bright-Star type of sandbox with tip toes screwed into the subchassis. An arm cable could easily be routed out the bottom of the table in conventional fashion this way. Another thought I had was to (perish the thought) build RCA jacks into the back of the armboard somehow (hardwired to the DIN plug) & use conventional interconnects to the phono stage. I suppose that you "lose" the extra plug connection on the turntable side by hard wiring the interconnect into the phono stage if this put a burr under your saddle. I'm guessing that the armboard will be either 3/4" or 1.0" acrylic in order to get the arm at the correct height for VTA adjustment. Accomodate an Outboard Motor Pod: This seems to be a feature of many of the "extreme" turntables like the Verdier and VPI TNT & I believe that the Scheu is one of these. If space is a consideration, Well Tempered's idea of a cutout in the plinth/subchassis would work quite nicely. The motor pod would look like a block that was cut out of the subchassis. This is certainly an area left to everyone's individual space requirements and sense of aesthetics. ----- Original Message ----- From: Schei, Kenneth [mailto:SCHEIKE@asa.org] Sent: Friday, December 17, 1999 8:40 AM Subject: Re: Scheu-Subchassis Igor: I've added "trilobial" to my vocabulary. I, too, have been thinking about a multi-level acrylic base after seeing one. Perhaps with brass spacers or an exotic suspension fabricated out of dumpster (or garage-sale) components. I'm not sure whom you're referring to as second-best, the Clearaudio Reference System or ours. Ken ----- Original Message ----- From: Igor Kuznetsoff Sent: Sunday, December 19, 1999 12:04 AM Subject: RE: Scheu Turntable Project --- ken schei wrote: > Igor: The best way to find out what's best is to > run a turntable both with > and without idlers and let our ears decide. > > Ken > Makes sense, but it does mean building at least one with idlers so that it can be played with & without. Attached is something I wrote earlier, before seeing the mail, and it contains my latest thoughts on the matter, and some ways that could be used to implement the possibilities, including some possibilities for building the idlers cheaply. See what you think. I ----- Original Message ----- From: Steve Zettel To: Chris Brady Sent: Monday, December 27, 1999 5:42 PM Subject: Re: Scheu Info Just a random musing about a few thoughts that came to me when I was thinking about the design of the turntable. I think it would be neat to have provisions for mounting two tonearms, perhaps 180 degrees apart for balance considerations. I have seen pictures once or twice of ultra-high end tables with two arms. Some advantages would be in the comparison of cartridges, allowing two different carts to be mounted and aligned and ready for A/B'ing without a lengthy lag time between each. Another possible use might be to have a less expensive cartridge ready at hand to play any suspect used LPs before sending the more expen$ive stylus/cantilever down an obstacle course. Or given two identical cartridges (Ha!), it would allow comparing different arms. . . Since most of my so-called LP "collection" is used, the second use would probably be the most common for me, and wouldn't even require two identical tone arms. Another area I have been thinking about has been suspension or lack of one. Until recently I had always considered a sophisticated suspension to be a necessary part of a turntable. Probably because the only "serious" turntable I have used is my present Oracle Delphi, which makes quite a big deal about their suspension system. For those not familiar with the Delphi, the platter bearing well is bolted to a subchassis shaped sort of like an angular amobea, with three extensions coming out to rest around and on top of the suspension towers, and a fourth extension for the armboard. The bottoms of the suspension towers are fastened solidly to the rectangular, unsprung lucite base. The motor is also fastened to the base, with a slightly resilient neoprene shock-mount. A rubber drive belt forms the connection between motor pulley and platter. The subchassis actually "hangs" from dampened springs in tension, inside the towers, rather than resting on top of springs in compression. Since the assembly is not symetrical, and one's selection of arms can vary dramatically in mass, sets of springs of various strength are provided to allow balancing, leveling, and frequency tuning of the suspension. It seems very effective, if somewhat tweeky to get it just right. However, I see and read about other highly regarded tables that have no, or very rudimentary suspension, perhaps more accurately just vibration dampening. I'd like to learn more about these and others' thoughts about them. I have to admit at first glance, something seems intrinsically wrong to me about touting a suspensionless design, and in the same breath noting that it is resting on special stands, $$$$ of dollars of isolation devices, or active air-suspension tables designed for electron microscopes! Since I have several sets of Oracle suspension springs, collars and dampers, including the heavy ones for more massive arms, I had planned on fabricating my own delrin towers and simple brass lead-screw adjusters, a la Delphi. But I am more than willing to be convinced to spare myself the extra work, if there is a compelling argument to be made for suspensionless turntables. Thanks for your input. Steve Z ----- Original Message ----- From: Igor Kuznetsoff Sent: Tuesday, December 28, 1999 12:19 AM Subject: Re: Scheu Info Guys, Judging by the lack of reaction to my suggestions about inner tubes,it looks like you just don't believe that something as cheap as the $3 (K-Mart / Target / WalMart, or $5-6 in any bike shop) inner tube can work as well as I've claimed, but I'm not all that surprised. Don't be fooled by how cheap & oversimple it seems. Something *doesn't* have to be complicatedly hi-tech, written up in a magazine, or seen on TV to be "official" enough to work, and work well. I'm not all that surprised by the non-reaction to my previous suggestion about the tubes, I've seen this before. During the '80's I talked myself blue in the face trying to get people to do something about the acoustics of their rooms, but, at best, I got a little bit of polite "lip service" for the concepts. Now there is a roaring business in acoustic products. Now that acoustics *officially* is recognized, and the subject has become an *expensive* thing, it has become credible. Around '90, I tried to get people to use cheap ferrite cores on wires in RF noisy situations, before anyone had heard of doing that. That, too was difficult sledding until expensive versions of these things meant for "audiophile use" became big (enough) business to become "acceptable" (through parallel thinking, so far as I know, it was a natural solution with already existing materials). Now I am saying, again "try this, you'll love it", and it's *cheap* ! There is no need to spend ~$360 on a Seismic Sink (which has an air bladder in it, with an official-looking case around that, for eyewash & "value building"), or up to $5K (!) for the automatic version of the electron microscope stand. And there definitely *is* a need for a suspension *somewhere* in your vinyl playback system. A "suspensionless" table only works well if you then put it on an "external" suspension, and/or expensive stand ! A good suspension does not have to be complicated, expensively machined, or impressively techy to work well, unless cosmetic eyewash is more important than cost effectiveness. There is technical elegance in effective simplicity. Anything involving metal springs, no matter how damped, will be too resonant or too stiff to be terribly effective. Other solutions exist, but the best and most effective usually involve air, note the Walker Proscenium with its "automatic air suspension" (built in), for instance. The air then has to be held in something, and what could be better than what lossy speaker surrounds are often made of these days, butyl rubber. Guess what inner tubes are made of ? Inner tubes are easily adaptable to an amazing variety of situations, with only a modicum of ingenuity & handiness. Doesn't DIY involve handiness, ingenuity, money saving, and the flexibility to try novel, elegantly inexpensive, *novel* approaches ? Isn't there a certain satisfaction to accomplishing more for less, and going *beyond* imitation ? Tubes are good. Some glow and make good sounds, some don't and absorb sounds good. **Try** them, you'll like 'em. I ----- Original Message ----- From: Mackris, Thom G. Sent: Tuesday, December 28, 1999 9:32 AM Subject: RE: Scheu-Subchassis Steve, Igor speaks the truth about air suspension. I can vouch for his early efforts (which mostly went ignored) in acoustic treatment, ferrite RFI blockers & cheap bicycle tube bladders. Setting up an air suspension does take some tuning however. I've often wondered about how 'tables like the Immedia & Roxan could possibly be optimized without some form of isolation or suspension. I honestly haven't read much about them so I can't fully comment. Two weeks ago, Thomas Martin came over & I got out my trusty inner tube to experiment using air suspension with my Merrill. I've been using an inner tube underneath my CD player for several years now, but have not gotten around to playing with one under my turntable, due to height problems fitting one inside a custom dust cover that I built (too complex to describe at the moment). A bit of background is in order about my previous turntable stands & experimentations. The Merrill is a 3 point suspended subchassis with *very* soft springs compared to say a Linn or a Thorens. I've found that as far as stands are concerned, the Merrill prefers to sit on a Linn type of stand - light and rigid. This is most curious, considering that Merrill's Stable Table is quite massive. I'll comment more about this in a moment. The "best" of the two light 'n rigid stands that I've tried to date is the Archi Dee stand that John Atkinson used to tout for the Linn. I have not tried the Mana stand that most of the folks at The Listener magazine have been raving about. To visualize the Archi Dee stand, picture a rectangle made out of 3/4" square tubing perhaps 4' wide by 14" deep. Now fold the rectangle upwards in two places along the wide dimension so that when viewed from the front, you see a squared off "U", and when viewed from the side, you see an upside down "U" ... kind of Escher-like. Anyhow, the stand is spiked at the top and bottom, with a "Torlite" top plate. Torlite is some kind of MDF / honeycomb product which was developed by Russ Andrews 15-ish(?) years back. Russ used to make a sub-chassis for Linn LP-12's out of this stuff. My other stand was a stock Linn stand. I had at one time tried all 4 permutations with these two stands, mixing & matching the stands & their top plates, and the Archi Dee with the Torlite was the superior combination. Additionally, I had tried a 3/4" thick piece of MDF on the Archi Dee which did not do as well as the Torlite on the Archi Dee. When I had a Sota, I was inspired by Merrill's first stable table & built my own version of it, a 3 shelf affair with a sand box which formed the bottom shelf, a triple layer of MDF for a center shelf, and a triple layer, MDF top shelf which sat on up turned tip toes. When sand-filled, the whole affair must have weighed 200-250 lbs. There was a substantial improvement in the Sota's performance (over siting it on the Linn table) with this stand - reduced noise floor, improved dynamics, etc. When I sold the Sota and bought the Merrill, I expected the same relationship between my "stable table" and the Linn Sound Organisation stand (I expected better sound with my stable table than with the Linn table) to exist, especially since Merrill was marketing his stable table for use with his turntable. I found quite the opposite to be true. When sited on my "Stable Table", the Merrill's sound was muted, and dynamics were squashed. Perhaps George does something else with his version of his stand other than damping with mass. I really can't comment about this. The point of this diatribe is that if you have something adjustable like an air suspension, it will take some tweaking to set up just right. Thomas Martin & I played with an air suspension arrangement by siting the Merrill on top of my double wide MDF equipment stand (triple layer top & bottom shelves & two single layer center shelves). The arrangement was: Turntable ==> Torlite Plate ==> Air Bladder (inner tube) ==> Equipment Stand. Without belaboring the point too much, let me say that we approached the sound of the Archi Dee but did not quite get there with the air bladder. Had we pursued this further, I'm sure we could have gotten to the Archi Dee's sound. The problem we had was that we *only* tried 4 inflation pressures, since I did not have any means of extending the valve to make adding/removing air a simple task. Without a valve extension, each different inflation took several minutes to effect, as one person held the table & Torlite plate, while the other person either bled air out or pumped more air into the tube. The table then had to be re-leveled on this whole affair which took 2 or 3 minutes. A means of running the valve extender through an accessible hole is absolutely necessary in order to get the table set up just right. At that point, you'd be able to take a pressure reading with a tire guage & be able to get there again with a couple of pumps every month or so. Is all of this worth it?? For my Merrill, I just don't know how much better I can get things than my current setup & I'm therefor not all that motivated to mess around much, especially with 3 cats & the custom isolated dust cover affair which I built. Perhaps I'd be pleasantly surprised if I tried. When starting from scratch, however, it seems as if it would be a whole lot easier to change spring rates by bleeding out or pumping in a bit of air than playing with individual sets of springs. Well, there you have it ... a beginning at least. Cheers, Thom ----- Original Message ----- From: Mackris, Thom G. Sent: Tuesday, December 28, 1999 9:56 AM Subject: RE: Scheu-Subchassis Steve, I've often wondered what those two arm rigs were all about. I didn't know if they were for cartridge/arm flexibility as you noted or perhaps for some other strange reason - perhaps running both arms at the same time for some kind of load balancing. Although I'm personally not as interested in adding more complexity to this design, certainly making the provision for accomodating a second arm as an option sounds like a simple thing to do. As the percentage of my record collection (~1300 LPs) approaches 50% used and will at some point, tip the balance with more used than newly purchased records, I share your concern for knowing where a record has been before playing it. I've found that my vacuum cleaning system is just fine, however & have no great concern about droping my stylus on "unknown" vinyl as long as I've cleaned it first (one of my rules that I follow about used vinyl). Perhaps if I had a multi-kilobuck cartridge, I'd feel more cautious, I don't know. My current record cleaner is essentially a VPI knock-off. My frien Bob (who introduced me to Merrills) in Arizona has a friend who designed a manual version of the VPI cleaner. He was never able to market it successfully and is subsequently not actively selling this unit, although I'll bet he has some stashed in his basement. The unit is a platter which sits inside of an oak box. The platter is turned manually via a glass center clamp which has a depression for your index finger. There's an "O" ring on the bottom of the clamp to keep the cleaning fluid from attacking the label. He supplies it with a modified edge cleaning tool which you use with your own vacuum cleaner. I picked up a small, rebuilt hand-held Hoover at a repair shop for $25.00 which works great. Being manual, you can rotate the record in both directions, just like the $700 VPI HW-17 !! The weak point of his system is (a) the fluid which I consider to be too noxious to be near vinyl and (b) the felt cleaning pad (which resembles the old diskwasher pads which were mounted in walnut handles. I use a VPI nylon brush to apply my home brew fluid & scrub the LP. The cleaning fluid recipe was taken from Laura Dearbon's book "Good Sound" - 25% lab grade Isopropyl, 75% distilled water & 10-12 drops of Triton-X wetting agent per gallon. Because home brew fluid is so cheap, I really saturate the record with no fear of leeching out the plasticizers in the vinyl. There seems to be a good enough track record with alchohol based record cleaning fluids. BTW, I have an infinite supply of the Triton wetting agent if anyone is interested - I had to buy a pint of it, and at 10-12 drops per gallon, you can guess that I have enough to offer some to anyone who's interested in brewing their own cleaning fluid. Let me know. Cheers, Thom ----- Original Message ----- From: Mackris, Thom G. Sent: Tuesday, December 28, 1999 12:19 PM Subject: RE: Scheu Info Thanks for pumping the German in the Scheu turntable site through Alta Vista / babelfish translator, Chris - As you noted to me by phone yesterday, it's amazing how many English words there are in the translation compared to how little of it gives any insight into Scheu's design. The engineering drawings which Alex forwarded to me along with the writup are certainly helpful to some extent (offer still stands to mail a copy to anyone who'se interested). I printed off the translated pages and found one item of note as I was dozing off on Sunday night. It had to do with a comment about the position of the motor "pod". I couldn't tell from the context whether they were merely talking about positioning the motor pod to optimize belt tension *or* whether this positioning was related to using belts of different lengths. If they were talking about the latter, then this plays out along the lines of Igor's analysis of incremental loading & unloading of belt tension and of the possible effect of changing distances between the various contact surfaces. Of course in Scheu's implementation there's only the motor pulley & the platter (no idler pulleys), but this still could be meaningful. Cheers, Thom ----- Original Message ----- From: Steve Zettel Sent: Tuesday, December 28, 1999 12:48 PM Subject: Re: Scheu Info I'll take Igor's reply as part suggestion for a simpler, more effective suspension, and part corroboration that indeed, *some* sort of suspension, or at least vibration isolation, is a necessity, even for suspensionless tables. FWIW, I have changed part of my current ttable set-up and am using a simple bicycle inner tube under a slab of Corian(tm) counter-top material. The Delphi is now sitting on this, rather than being suspended via surgical tubing from a massive shelf loaded with albums above. I am still evaluating which method I prefer, but the bicycle tube seems at least the equal of the suspended turntable for all except very heavy footfalls in the area of the turntable rack, or dancing up and down with wild abandon on the somewhat spring family room floor. A smaller tube and smaller slab under the Super IT have made positive improvements in vinyl playback, as well. Short of cleaning out the garage and turning it into a dedicated listening room (not in THIS lifetime, unless I get a kitchen and two bathrooms remodelled first!), I don't have a concret slab floor anywhere in the house. Steve Z ----- Original Message ----- From: Igor Kuznetsoff Sent: Tuesday, December 28, 1999 2:58 PM Subject: RE: Scheu-Subchassis I vouch for Thom's vinyl wash formulation, "Thom's XXX". I've been using it for years since he sent me a bottle, and like it much more than the Audio Advisor stuff I used before that. Like Thom, I also find that a liberal application of a kinder formulation helps to float off the gunk better than the sparing use commonly recommended, especially for that critical first cleaning of used records. (Thanks again, Thom). I ----- Original Message ----- From: Igor Kuznetsoff Sent: Tuesday, December 28, 1999 5:22 PM Subject: Re: Scheu Info The surgical tubing is a very good idea! I did something vaguely like that with a noisy dehumidifier which I suspended above a utility sink (which it drained into) using EPDM bungee cords arranged in a network to keep it from making noise which interfered with one of my listening rooms. Probably the only way to avoid the footfall problem would be wall mounting, because the amplitude (high) & frequency (very low) of the foo-falls is almost certainly beyond the resonance passband of the 'table weight / tube compliance combination to tune out. Or make the 'table much heavier, somehow,like siting it on a sandbox, so that the table/box mass is much harder for the vibration to move. You'd be surprised by how much a tube can hold (with increased inflation). Thom is quite right about tuning the air pressure in the tube to achieve optimum passband tuning. Theoretically, two tubes at different pressures (with a plate in between) should be tuneable to a (near)zero passband state, another (if complicated) possibility. See the other of today's posts for a tip on how to make tuning inflation easier. --- Steve Zettel wrote: > I'll take Igor's reply as part suggestion for a > simpler, more effective > suspension, and part corroboration that indeed, > *some* sort of suspension, > or at least vibration isolation, is a necessity, > even for suspensionless > tables. > > FWIW, I have changed part of my current ttable > set-up and am using a simple > bicycle inner tube under a slab of Corian(tm) > counter-top material. The > Delphi is now sitting on this, rather than being > suspended via surgical > tubing from a massive shelf loaded with albums > above. All Right ! Have you considered a combination *of both* of these excellent techniques to effect complete isolation ? I realize that it could get a bit complicated, but it could be just the thing for realizing a "zero passband" ! You could try suspending the Corian shelf by the surgical tubes, then site the inner tube on that, and top that with an MDF shelf (to keep the materials' resonances dissimilar) with the table (or even a sandbox) on that. The Corian & MDF can be interchanged as is convenient for ease of construction, or cosmetics. With the table hung by tubes, sitting on tubes, preamped by tubes, amped by tubes, all you would need to be totally tubular would be T-Lines made out of tubes....Sorry, I let that get away from me. Anyway, on the serious side, I hope this is doable & of interest, because I'd love to hear about how this works. > > I am still evaluating which method I prefer, but the > bicycle tube seems at > least the equal of the suspended turntable for all > except very heavy > footfalls in the area of the turntable rack, or > dancing up and down with > wild abandon on the somewhat spring family room > floor. > > A smaller tube and smaller slab under the Super IT > have made positive > improvements in vinyl playback, as well. All tube equipment is microphonic, and can benefit from vibration isolation. The higher the gain in the circuit, the more sensitivity can generally be expected. However, I've found that even tube *amps*, because of their driver tubes, primarily, can be improved with cleaner sound (particularly in their noise floor). Inner tubes can handle quite a bit or weight (especially if you go to the 16" size), but in extreme or hard to balance situations, I've even used used (no typo, I mean *beaten up*, as in recycled) racquetballs set into either spray paint can tops (just the right size on typical cans to retain/locate them) or plates with appropriately sized holes cutout to control ball location. The r-balls may not have quite the compliance and isolative capabilities of the tubes, but they can handle massive weights, with good lateral stability. Additionally, you will then be able to legitimately claim that your amp truly has "balls", no matter how little power it actually has ! Oh, and they can be painted black (or whatever) using automotive flexible paint meant for vinyl upholstery & bumpers, should you not want "blue balls". They also come in a green competition version nowadays, but those are a bit more expensive, and less convenient to collect. If you are not a player, they are thrown out in large quantities at any r-ball court, because they soften quickly after being viciously smacked around by a modern racquet. Choose the softest, keep spares (just in case you get one that is just about to pop) > > Short of cleaning out the garage and turning it into > a dedicated listening > room (not in THIS lifetime, unless I get a kitchen > and two bathrooms > remodelled first!), I don't have a concret slab > floor anywhere in the house. Even that is only good if you are more than 1/2 a mile (min) away from train tracks or 1/4mi (min) from bus routes. I discovered just how far very low frequency vibrations can travel through some soil compositions in the course of doing RTA measurements during speaker tuning. A long train can really interrupt your work ! ----- Original Message ----- From: Igor Kuznetsoff Sent: Tuesday, December 28, 1999 6:39 PM Subject: RE: Scheu-Subchassis I have long thought that the reason that there seems to be so little obvious predictability in whether a massive or light/flimsy TT stand will work best with any given 'table is a matter of "passband tuning", which is a matter involving the combination of the physical parameters of the 'table, stand, floor mass/compliance/covering, floor/wall construction, etc. ***in the absence of proper acoustic decoupling of the turntable from the rest***. > Setting up an air suspension does take some tuning > however. Critical. This is what makes the technique work with the ultra-sensitivity of the vibration-driven system of a turntable. Less critical with other components, but with 'tables, it's tuning, tuning, etc. >The problem we had was that we *only* tried 4 > inflation pressures, since I > did not have any means of extending the valve to > make adding/removing air a > simple task. Without a valve extension, each > different inflation took > several minutes to effect, as one person held the > table & Torlite plate, > while the other person either bled air out or pumped > more air into the tube. > The table then had to be re-leveled on this whole > affair which took 2 or 3 > minutes. A means of running the valve extender > through an accessible hole > is absolutely necessary in order to get the table > set up just right. Very true. A major PITA without an extension, which costs about $1/tube plus the bigger expenditure of about a 1/4 to 1/2 hr (once you have the parts & technique) per tube. Use a (long version) "valve extender" such as you can buy at any auto parts store, or K-Mart, Target, W-M, etc for ~$2/3 or 4 in a pack, plus whatever footage you may need of thick-walled black rubber tubing in (usually) the smallest size that auto parts stores carry, and some super-glue (preferrably in hobby/industrial grades, not the junk supermarkets sell), or try your own choice of glue. The valve extenders are just replacement valve stems in a longer length, such as might be used on a truck rim. The tubing should be a *very* tight fit, so you can barely jam it onto the valve stem, with the help of the unset glue. Start by removing the original valve with any (cheap) stem tool (K-M,T, W-M, etc. if you don't have one). Cut the tubing to length, and glue onto the (inner tube) stem. The glue will lubricate the effort. Then remove the (grooved, shaped) rubber end of the valve extension *verrrry carefully* from the underlying threaded brass body with a utility knife. The rubber is bonded hard to the brass, the piece is small and hazardous to hold, and this operation can result in blood if not done cautiously, beware ! Avoid distorting the brass body-use of a vice or vice-grips not recommended. If you can find something larger to screw the threaded end into for a handgrip, do that (I got by safely without). Once you've cleaned off the rubber (be prepared to sacrifice a blade), glue that into the waiting end, and leave overnight to be sure of a good cure. Done. > Steve, > > Igor speaks the truth about air suspension. I can > vouch for his early > efforts (which mostly went ignored) in acoustic > treatment, ferrite RFI > blockers & cheap bicycle tube bladders. > > Setting up an air suspension does take some tuning > however. I've often > wondered about how 'tables like the Immedia & Roxan > could possibly be > optimized without some form of isolation or > suspension. I honestly haven't > read much about them so I can't fully comment. Two > weeks ago, Thomas Martin > came over & I got out my trusty inner tube to > experiment using air > suspension with my Merrill. I've been using an > inner tube underneath my CD > player for several years now, but have not gotten > around to playing with one > under my turntable, due to height problems fitting > one inside a custom dust > cover that I built (too complex to describe at the > moment). > > A bit of background is in order about my previous > turntable stands & > experimentations. The Merrill is a 3 point > suspended subchassis with *very* > soft springs compared to say a Linn or a Thorens. > I've found that as far as > stands are concerned, the Merrill prefers to sit on > a Linn type of stand - > light and rigid. This is most curious, considering > that Merrill's Stable > Table is quite massive. I'll comment more about > this in a moment. > > The "best" of the two light 'n rigid stands that > I've tried to date is the > Archi Dee stand that John Atkinson used to tout for > the Linn. I have not > tried the Mana stand that most of the folks at The > Listener magazine have > been raving about. To visualize the Archi Dee > stand, picture a rectangle > made out of 3/4" square tubing perhaps 4' wide by > 14" deep. Now fold the > rectangle upwards in two places along the wide > dimension so that when viewed > from the front, you see a squared off "U", and when > viewed from the side, > you see an upside down "U" ... kind of Escher-like. > > > Anyhow, the stand is spiked at the top and bottom, > with a "Torlite" top > plate. Torlite is some kind of MDF / honeycomb > product which was developed > by Russ Andrews 15-ish(?) years back. Russ used to > make a sub-chassis for > Linn LP-12's out of this stuff. My other stand was > a stock Linn stand. I > had at one time tried all 4 permutations with these > two stands, mixing & > matching the stands & their top plates, and the > Archi Dee with the Torlite > was the superior combination. Additionally, I had > tried a 3/4" thick piece > of MDF on the Archi Dee which did not do as well as > the Torlite on the Archi > Dee. > > When I had a Sota, I was inspired by Merrill's first > stable table & built my > own version of it, a 3 shelf affair with >a sand box An excellent addition to TT mass, making decoupling more effective. An excellent adjunct, particularly when decoupled, but, as with everything in analog, a matter of *tuning*. ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Saturday, January 01, 2000 3:47 AM Subject: Re: Scheu-Subchassis All, I'm not sure if this one goes under Subchassis or "Bearing & Platter". Anyhow, it's 3:30 AM, I can't sleeep, I have to get to work in four and a half hours & I'm fighting a cold. All I see when I close my eyes is turntables, suspensions & motor configurations. I keep trying to envision a subchassis sitting on an open topped sandbox, or perhaps on tip toes which then rest on the floating top plate of a sandbox. I'm having problems locating the motor pod. If the pod sits on it's own plate - an island if you will, then I can't imagine it staying in place as the belt tension would either tilt it or pull it toward the platter. If it sits on the base of the sandbox, it would be more stable. Perhaps we need a divider along the left side, allowing something like a 3.5" wide area which would house the motor pod at the rear, and the controller, speed control switches & trimmer pots at the front. This would certainly form a nice, neat area for these components. The controller & switches/pots could be mounted on a plate which covers the entire channel and the motor pod (housed in some sexy looking cylinder) could protrude through a circular hole in the rear. The pod could be built around a piece of PVC pipe. If the subchassis rests on tiptoes on top of a floating top plate, we'd still have a fairly sexy looking rig. The whole sandbox, top plates & motor pod could be finished in Hammerite or some other tough, high gloss finish. An alternative to the plate at the left would be to build all of the components into the PVC tube and cover the sand with the black decorative sand that Igor mentioned a while back. Could the components tolerate being encased in sand inside the tube? Would we have to leave some air space and vent it with a few holes? We'd have to have switches coming out of the PVC or the top plate which might not be too ergonomic. +-------------------------------+ | | | |( Motor ) | | | | | | | | |Controller| | | | | | | Subchassis | | | | | Switches | | | | | | | | | | | +-------------------------------+ Top view of divided sandbox An alternative would have the motor pod sitting outboard of the sandbox, but then the problem arises of the pull of the relatively fixed motor against the suspended subchassis/sandbox assembly which floats on the air suspension (inner tube). This would be a problem whether the inner tube is in the sandbox (underneath either the top plate of the sandbox or directly under the subchassis) or underneath the sandbox. Additionally, adjusting the relative height of the motor pulley would be a real nuisance. While you played with optimizing the pressure in the inner tube (changing the platter height relative to the pulley) you would need some means of adjusting the height of the motor pod (threaded spikes?). Additonally, you would still have the destabilizing force of the pull against the table from one direction. I can envision if we went in this direction, that a second pulley would be necessary. This pulley would have to be 180 degrees opposite the motor and housed in its own freestanding pod. One of the purported advantages of the Roxan Xerxes table was the fact that the belt wasn't pulling against a suspension, rendering better pitch stability. The Roxan had other problems (I've heard that a section of the plinth fatigues over time), and I can't figure out how they killed vibrations with no suspension other than the funky grooves in the top plate, but that's a whole other topic. Anyhow, my mind is getting fuzzy over this, although I'm still not sleepy. Hopefully this prompts some constructive criticism from you all. Yappy who near, happy gnu year, or something like that ... Thom ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Sunday, January 02, 2000 7:02 PM Subject: RE: Scheu-Subchassis All, I came across a turntable review by Art Dudley (The Listener v5 #3) of the Nottingham Analog Hyper Space Deck. Since Igor and I were having a conversation about Art, I thought I'd mention some of the salient points of this 'table's design. While I don't agree with Art completely, he does write intelligently & I appreciate this a great deal. I never understood Art's unabashed devotion to Linn, but I guess that's what makes horseracing. Art makes an provocative comment about BIG turntables - that most of them are impressive, making a big sound, but ultimately end up boring him. This particular deck is a BIG deck, but doesn't bore him. There are a lot of elements of our design in this deck, although Nottingham uses an AC motor which has *just* enough torque to keep the platter spinning. It's plugged directly into the wall (no power supply) - you nudge it to get it going and stop it with your finger. Other than this (AC motor) the design serves as a remarkable validation of where we're going. The bearing spindle is 1/2" thick. I've been pondering a thick bearing spindle & I don't know why. Could there be some minimal flex in the spindle that would make this worth while or is this overkill? The platter weighs about 30 lbs. and the 'tabtle is an open chassis design. The subchassis is round, approximately an inch thick - it looks like a second (thinner) platter sitting beneath the platter. This subchassis sits on 3 hockey pucks spaced 120 degrees apart - the pucks appear to be about 3" thick. A round armboard attaches to one of the "pucks" and the motor attaches to another. These pucks rest on what appears to be a Corian (tm) base. The motor pulley is fairly high mass to smooth it's vibratons out at the source. I'll photocopy the article & set it aside with your motors. Cheers, Thom ----- Original Message ----- From: Alex Mitaru Sent: Tuesday, January 04, 2000 6:56 PM Subject: Re: Scheu-Subchassis Some years ago, I got a small sample of a new plastic material called "Norsorex" that was advertised as an excellent vibration damper and they (I think Madisound) were trying to sell it as speaker gaskets. The demo was to through a coin to the piece of Norsorex and to a piece of regular plastic foam; it was amazing, while the coin bounced of the regular foam, it seemed that it was sucked by the Norsorex to a stop, it is hard to describe, but it looked almost unreal....well, since then I tried to find some suppliers of Norsorex (it is supposedly sold in 1/8" sheets) but couldn't find any...Edmund Scientific used the sell a "happy ball" and a "sad ball", the "sad ball" being made of Norsorex, and several folks used those balls as support for equipment with good results... I was thinking, maybe the sub chassis might be built as a sandwich with Norsorex in the middle... cheers, alex ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, January 05, 2000 2:55 AM Subject: Re: Scheu-Subchassis If you set a top plate on the sand, you will give up much of what the sand can do for you. The plate will contact the sand only at high points, and will not be able to sink vibration into the sand very effectively, and that plate will have a tendency to creep towards any pull, besides. All that you will get out of that will be the mass of the sand resisting whatever vibration is transmitted upward from underneath the box it is in. If you attach a set of cones (tiptoes, etc.) to the subchassis positively (screw/glue/whatever) and also a set to the motor pod, and press these firmly into the sand, all should stay put just fine, so long as you do not tighten the belt to the point of being able to shoot arrows with it. Set up two of the three cones under the motor pod towards the direction of the pull, and use the widest base under the motor that your layout allows for stability/tilt resistance. If you divide the sandbox into two foam-rubber lined compartments as previously suggested, the motor will be isolated acoustically from the rest except at the belt, and have its own patch of sand to sink noise into. This leaves the question of the side pull against the inner tube. I can think of three practical variations in the use of the tubes. The first & simplest would be to place one under the sandbox to stop whatever vibration is coming up the stand, and depend on the divided sandbox and the inherent ability of the sand itself to sink noise plus the large mass of the platter to handle whatever is within the system itself. In this arrangement, adding the rubber chips I wrote about would be particularly helpful. This layout would, I expect, result in especially solid bass, but may or may not yield the lowest noise floor, compared to the following. The next variant would involve inserting a tube between the platter - carrying subchassis and the sandbox. You would want the tube to sit between the platter/chassis and another chassis element of whatever shape strikes you ("trilobial" like the Clearaudio, if you like). The bottom element would have the cones attached to it, and set into the sand. This would isolate the platter & arm from everything but the belt most effectively, but will not allow a conduction path for any vibes from the bearing (should there be enough such to talk about), or from the stylus (via the arm) to the sand for sinking therein, should you be of that design philosophy. It will also result in a lower total linked mass involving the platter / subchassis assembly than the previous scheme, which links those solidly to the sand. Alex Mitaru's suggestion of a Norsorex (or equivalent) laminated chassis element(s) would be a particularly good idea in this arrangement, as would extra mass such as we would gain from the additional lamination be. It would also, as Thom points out, create a side pull on the soft, flexible inner tube, which would have to be balanced out in this configuration, as he figures, with (yet another) balancing idler. This gets pretty complex if we are to drive a balanced two idler system with a system involving the motor and yet another idler to balance the pull of the belt on the driven (main) idler of the isolated system consisting of the platter & two (main) idlers floating on a tube (plus, of course, arm). This would require an additional subchassis carrying the motor and *its* balancing idler, and the complication of isolating that from the main pocket of sand at the idler end, as well as the problem of height adjustment. Without the motor balancing idler, as he observes below in the comment about the Xerxes, there would be the likelihood of a rocking motion being imparted to the entire assembly, even with the respectable mass of the platter's 5 Kg plus other parts not wanting to rock 'n' roll too easily. The third variant would simply involve adding a second tube under the sandbox of the second version to isolate the system even better from floor - borne / stand transmitted vibration. This would allow the possibility of tuning the two tubes to different pass frequencies, to approach a "zero passband" system which would filter out all frequencies attempting to reach the stylus. The bottom tube is the one, I feel, that would do most of the work, actually, because it is immediately followed by the largest mass. As the second and third variations would be very difficult to both build and set up, I would suggest considering them intellectual exercises, and concentrating on the properties of the first. In that layout, I believe that the isolation of the motor from the transductive assembly would already be superior to anything I am currently aware of. And the effect of the inner tube under the sandbox combined with the sandbox itself should yield isolation from floor-borne vibration at least equal to, and most likely better than pretty much anything currently on the market, short of (maybe) only that $5K electron microscope stand, and for only as little as $3 ! So far as I know, most, if not all, suspension systems in turntables that have any at all are only designed to block the most damaging vibrations, which are the floor-borne type. So, what more do we need ?? Comments, suggestions ?? > An alternative to the plate at the left would be to > build all of the components into the PVC tube and > cover the sand with the black decorative sand that > Igor mentioned a while back. Could the components > tolerate being encased in sand inside the tube? > Would we have to leave some air space and vent it > with a few holes? We'd have to have switches coming > out of the PVC or the top plate which might not be > too ergonomic. Why not just build something like Scheu's motor pod, with the circuitry and switches on / in the pod, add the cones to the bottom, and just set the pod on the sand ? If the motor was outside the box, and the tube under it, the huge mass of the entire assembly would probably be more than enough to swamp the small side force presented by the pull of the belt. At most, it would "set", or "cock" the entire assembly a micrometer or two in its direction as a bias, and that would be that. Given the masses involved, it is not overly likely that the belt will be able to impart very much of lateral rocking vibration. This variation is probably uselessly moot, though, as this doesn't sound like a very practical physical layout, you would need a *very* large table to accommodate all this, and height adjustment *would* be awkward. And the belt length.... > Additionally, adjusting the > relative height of the motor pulley would be a real > nuisance. While you played with optimizing the > pressure in the inner tube (changing the platter > height relative to the pulley) you would need some > means of adjusting the height of the motor pod > (threaded spikes?). Adjusting the heights could be simply a matter of pressing the cones (attached solidly to their assemblies) into the sand / lifting them to desired levels, which is very easy. The sand can provide a good deal of side force resistance when the cones are pressed deeply enough. For this reason, fairly tall cones are desirable. Be sure to check leveling when done. To make this easy, "bullet" type bubble levels can be incorporated permanently into the design. They need not be expensive, they can be as cheap as a couple of dollars apiece, so long as they look good enough to not cheapen the overall cosmetics. The trick would be to calibrate them against a high quality level while setting them in a (thickish) bed of glue, such as fast epoxy or thick-gel type super glue. Fast setting is desirable to be sure that the level stays calibrated until it can no longer "creep" out of position, while you keep an eye on it. Many cones that I have seen do come with threaded centers, allowing the possibility of setting up a threaded "fine adjust", if you like. ----- Original Message ----- From: Mackris, Thom G. Sent: Wednesday, January 05, 2000 11:12 AM Subject: RE: Scheu-Subchassis I received one of my (seemingly) semi-monthly Audio Advisor mailings yesterday. In it, they were pushing a VPI TNT 'table. I noticed that VPI is doing what I was suggesting as far as the idler pulleys are concerned ... keeping them on separate "pods" isolated from the subchassis in the same manner as the motor. The idler pulley's pass through a hole in the subchassis. Thom ----- Original Message ----- From: Steve Zettel Sent: Wednesday, January 05, 2000 4:15 PM Subject: Re: Scheu-Subchassis Just a few comments re sandboxes, cones, and side-tension on drive belts and interactions with suspensions. 1. Why cones when placing the turntable in sand? The pointy end of cones in a conventional setting (resting on a hard, massy surface) is to provide a concentration of force and enhance coupling to the surface below. Embedding the support feet in a sandbox for lossy isolation would seem to make the conical shape unneccessary, other than for ease of pushing the unit down into the sand, and in some cases might make it easier for the tt to continue to migrate downward until the points bottom out on the bottom of the sandbox. Particularly with a massive tt assembly. Just a quick intuitive impression on my part, and not the result of a rigorous mechanical or materials analysis. (Thought experiment: foundation of house on underlying soil, or concrete support piers in sand or soil). 2. I think I mentioned before that I read of one of the "hot tweeks", and perhaps now even a VPI-sanctioned modification for better sonics was the elimination of the idlers and flywheels associated with the top of the line VPI tt's. I am not real familiar with VPI's, and have only seen the pictures in AA, so I may be misunderstanding what I read in the Phonogram e-mail list. 3. With a tt I *am* familiar with (my present Delphi), the platter/bearing/arm are all on a suspended subchassis. The motor, controls, and bottoms of the suspension towers are mounted on a sheet of acrylic as the chassis. The belt bridges the void between the motor/motor pulley (un-suspended, very slightly resiliently mounted to the chassis) and the platter (fully suspended). The very slight side-pull of the belt is negligible in comparison to the large mass of the platter/bearing/subchassis/arm and in practice does not interfere in the least with the leveling of the platter, statically or when the suspended assembly is in motion -- the subchassis assembly can be "bounced" with a finger and undergo excursions much wider than would ever be caused by a 180 lb man (me) jumping up and down beside the tt stand, and timing his leaps to excite the floor to resonance. The excursions occur in the vertical axis, and not side to side wobble occurs. As Igor observed, the belt certainly should not be bow and arrow tight, and in fact should be as loose as possible without slipping. This will effectively move the passband of vibrations transmitted by the belt much lower in frequency. In a sandbox, I would suspect that the relative motion between motor assembly and platter assembly would be next to nil; perhaps a very imperceptible creep towards one another at most. Steve Z ----- Original Message ----- From: Mackris, Thom G. Sent: Wednesday, January 05, 2000 4:43 PM Subject: RE: Scheu-Subchassis Damn this is a smart group of folks! 1. I think Igor's "point" (pun intended) was that when a flat surface (subchassis) sits on the sand, it is not as damped as when it is associated with the entire mass in the sandbox by contacting the bottom of the sandbox via cones which couple the subchassis to the bottom of the sandbox. If this is true, does it matter? I suppose that minimally it would make leveling that much simpler. Would it hurt instead of help? As I write this, I'm not sure anymore. Perhaps someone else can comment on this. 2. Indeed, you mentioned the VPI "tweak". I have to wonder if this "improvement" resulting from removing the idler pulleys wasn't a result of a poor turntable setup. I obviously don't know the answer to this one, and I'm not necessarily advocating idler pulleys when I say this. I just have to wonder however why Weisfeld would have designed the pulleys into the system. I have a hard time believing that he's incompetent. As we've all experienced (through our friends, newsgroups, etc.) people will make a series of tweaks, each one being an "improvement", only to remove them all, resulting in yet another "improvement". Just some idle thoughts on the matter. 3. Your Delphi describe my Merrill, and just about every other suspended 'table. Of course yours is gorgeous, without an external plinth. I honestly don't know how much merit there is to this whole side-pull issue, but Roxan, perhaps only to distinguish themselves from the "suspended" pack seems to claim that having the subchassis suspended (with the motor on the fixed plinth) results in speed instability. Beats me. I can certainly see that the more stable (massive) the subchassis/platter is, the less of an issue this would be. This all seems to be about trading off one compromise for another. Today's opinion (note the use of the word today) is that Igor's option #1 would result in a pretty good 'table. I'm still not clear however on the tip toe vs "floating" subchassis part of this analysis, however. His Option # 1 if I read hm correctly is much like what I was sketching out on my sleepless New Year's morning: a divided sandbox, (a) the left side of which holds the motor pod which is spiked to the bottom of the sandbox and (b) the right side of which contains the subchassis, also spiked to the bottom. The entire sandbox is supported on an sir suspension. I have to go back and read his analysis one more time, as I recall a second air suspension somewhere, but I'm not sure if it's in option 2 or 3. Cheers, Thom ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, January 05, 2000 6:35 PM Subject: RE: Scheu-Subchassis --- "Mackris, Thom G." wrote: > Damn this is a smart group of folks! > > 1. I think Igor's "point" (pun intended) was that > when a flat surface > (subchassis) sits on the sand, it is not as damped > as when it is associated > with the entire mass in the sandbox by contacting > the bottom of the sandbox > via cones which couple the subchassis to the bottom > of the sandbox. If this > is true, does it matter? I suppose that minimally > it would make leveling > that much simpler. Would it hurt instead of help? > As I write this, I'm not > sure anymore. Perhaps someone else can comment on > this. Perhaps more than minimally. Would you rather the tight coupling to the sand, or the possible (however minimally) resonant behavior of a flat plate, plus loss of coupling ? > 3. Your Delphi describe my Merrill, and just about > every other suspended > 'table. Of course yours is gorgeous, without an > external plinth. I > honestly don't know how much merit there is to this > whole side-pull issue, > but Roxan, perhaps only to distinguish themselves > from the "suspended" pack > seems to claim that having the subchassis suspended > (with the motor on the > fixed plinth) results in speed instability. Beats > me. I can certainly see > that the more stable (massive) the > subchassis/platter is, the less of an > issue this would be. In audio, mass seems to be a good thing except at shipping time or whenever movement is *desired*. Nice thing about sand is that you can leave it behind. > -----Original Message----- > From: Steve Zettel [mailto:zettel@libby.org] > Sent: Wednesday, January 05, 2000 4:15 PM > > 1. Why cones when placing the turntable in sand? The > pointy end of cones in > a conventional setting (resting on a hard, massy > surface) is to provide a > concentration of force and enhance coupling to the > surface below. Embedding > the support feet in a sandbox for lossy isolation > would seem to make the > conical shape unneccessary, other than for ease of > pushing the unit down > into the sand, You got it! Much easier, in fact, plus, as you add your own mass to push them down, the contact area increases quickly until it becomes difficult to press farther. remove your mass from that, and the resistance to further migration becomes quite large, making the system fairly self-limiting, unless you live in a frequent earthquake zone, or over a subway. Your analysis of the concentration of force is quite correct, and not only applies to sand the same way, but even more critically because sand behaves to some extent as a viscous substance, requiring progressive compression of the sand grains coupled with quickly increasing contact area as an automatic response to increasing pressure to effect deformation stability, which is *exactly* what a conical shape makes possible. That is why I've had a set of cones waiting for around 7 years, since I figured this out & fooled around with a mockup, just waiting for a chance to set up a TT just this way ! and in some cases might make it > easier for the tt to continue > to migrate downward until the points bottom out on > the bottom of the > sandbox. Particularly with a massive tt assembly. > Just a quick intuitive > impression on my part, and not the result of a > rigorous mechanical or > materials analysis. (Thought experiment: foundation > of house on underlying > soil, or concrete support piers in sand or soil). The trick will be to design / find the right cone cross-section (size / cone *angle*) to handle the mass we end up with in order to wind up with a stable, non-creeping system, just as in sizing the foundations / piers correctly. Have you ever heard of a "self-holding screw" ? Ask most experienced machinists - it is a (known) matter of using the right thread pitch. > > 2. I think I mentioned before that I read of one of > the "hot tweeks", and > perhaps now even a VPI-sanctioned modification for > better sonics was the > elimination of the idlers and flywheels associated > with the top of the line > VPI tt's. I am not real familiar with VPI's, and > have only seen the pictures > in AA, so I may be misunderstanding what I read in > the Phonogram e-mail > list. Dunno, but, then, that top Clearaudio has three *motors* !! > > 3. With a tt I *am* familiar with (my present > Delphi), the > platter/bearing/arm are all on a suspended > subchassis. The motor, controls, > and bottoms of the suspension towers are mounted on > a sheet of acrylic as > the chassis. The belt bridges the void between the > motor/motor pulley > (un-suspended, very slightly resiliently mounted to > the chassis) and the > platter (fully suspended). The very slight side-pull > of the belt is > negligible in comparison to the large mass of the > platter/bearing/subchassis/arm and in practice does > not interfere in the > least with the leveling of the platter, I suspect that *leveling* isn't the issue, but a microscopic, cyclical, "teeter-tottering" just like that which can happen at the platter from belt pull would be. Of course, we are now talking about a larger system, and concomitantly reduced amplitude. > statically > or when the suspended > assembly is in motion -- the subchassis assembly can > be "bounced" with a > finger and undergo excursions much wider than would > ever be caused by a 180 > lb man (me) jumping up and down beside the tt stand, > and timing his leaps to > excite the floor to resonance. The excursions occur > in the vertical axis, > and not side to side wobble occurs. > > As Igor observed, the belt certainly should not be > bow and arrow tight, and > in fact should be as loose as possible without > slipping. This will > effectively move the passband of vibrations > transmitted by the belt much > lower in frequency. Right ! I've long wondered if longer belts might also be a good idea. Has anyone experimented with this ? In a sandbox, I would suspect > that the relative motion > between motor assembly and platter assembly would be > next to nil; perhaps a > very imperceptible creep towards one another at > most. Much like glass flowing over the centuries. Did you know that the age of window glass can be dated reasonably accurately by how much thicker it is at the bottom than it is at the top ? I ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 06, 2000 12:20 PM Subject: RE: Scheu-Subchassis Since subchassis design seems to be one of two areas which has been discussed the most over the last month or so (the other area being platter & bearing design), I think it's time to take stock of some items. 1) Finalize the design: We'll probably want to finalize our thoughts in the next couple of months and solidify the design - say by the end of February. 2) Design flexibility: Our design should allow for some flexibility for varying functional as well as cosmetic approaches while being consistent with the goals of world class turntable. In other words, we should strive for the "ultimate", recognizing that practicality may result in some minor compromises - hopefully, the design can be generalized to accomodate all levels of "enthusiasm". 3) Decision making & voting: The active participants will have the most (exclusive?) say in this project, while at the same time trying to avoid any "tyranny of the majority". This will be in keeping with item #2 - design flexibility. Yesterday, I printed Igor's discussion on three subchassis options. Looking at them in print allowed me to picture them more easily. I would agree that option #1 is the ideal, flexible solution. If you recall, this option is the split sandbox option with the inner tube being placed under the sandbox. The left side of the sanbox would support/isolate all motor & controller related components and the right side would support/isolate the subchassis. My current reasons for this are: (1) I think that we could be still discussing how to pull off options #2 & #3 next year at this time. (2) I want to keep this as compact as possible. (3) This layout bears a strong similarity to the Scheu 'table, only far better damped and isolated. The Scheu seems to have a fairly enthusiastic following and *was* the springboard for this entire project. I haven't heard any other comments other than Alex's suggestion on some form of constrained layer sandwich for the subchassis, so I'm at this point assuming that some form of sandbox is acceptable to everyone. I'm going to get together with Chris & try to coordinate placing some preliminary "concept" drawings on his website for everyone's collaboration. One question which we have yet to explore is how BIG can we tolerate this critter being? I'm personally interested in striving for something relatively compact, realizing that this will still end up being a fairly large item. If I had to commit to an off the top of the head dimension, I'd guess it would be a sandbox that's 20"wide by 16" deep ... this is a preliminary number. Another area related to the entire project is: Has this become our design and not Scheu's? This would appear to be the case. Chris voiced his opinion to me a few days ago that even *if* we wanted to build a Scheu design from the plans, the German language would serve as a significant barrier to understanding all his critical design assumptions. We may think that we have it conceptualized, but we might be missing a critical point. Another significant barrier to building a Scheu from plans is cost. His bearing is quite complex and would most likely (a guess) cost $200 or more in the quantity we're talking about. This is about what he's charging for it. This price is in contrast to the estimate of $70 for a non-inverted, oil sump bearing. Anyone interested in a Scheu is best served by ordering directly from him as his prices are a "smokin" deal - he deserves the business at the prices he's offering his product for and the design is complete. Although we're doing this as an enjoyable project, I think that we have an obligation to the group to start to manage this professionally in order to keep things on course with respect to timetable and direction. After say, another month of bandying things about, I think we will need to start thinking about a real project schedule, complete with deliverables. Cheers, Thom ----- Original Message ----- From: Sent: Friday, January 07, 2000 7:57 PM Subject: Re: Scheu-Subchassis Hello, Brian Boehler checking in. A couple of quick thoughts: 1. I have read with great interest all of the thoughts and believe you are covering the needed bases from a technical standpoint. 2. I haven't given much in the way of input because I went through some of this a few years ago when I built my own turntable. Since I did not have the luxury of building many of the parts from design concepts that I had or from scratch, I purchased the platter, bearing assembly and motor/controller from VPI. These were all pieces from the TNT III or IV. 3. My contribution to the project was to construct a massive base and subchassis to house the VPI components. I prefer mass and weight and so I sat about constructing a base of MDF filled with lead shot. Many other odd and end tweaks also. I also constructed a sub-base filled with sand and a sandwich of steel/rubber/steel for the table to sit on top of. Total weight of the finished product was approximately 225 pounds. I mounted the VPI motor into a block of lead and had it on a different sub-base from the table. The only connection was the belt that drove the platter. I also bought a VPI turntable power line conditioner. To this contraption I mounted a Souther Linear Tracking arm and Souther cartridge. Through no fault of my own, my cartridge recently got broken (dog issue). There went $1200 down the drain. I'm still disturbed over this one and haven't bitten the bullet to replace it. Might consider some changes. On balance, I'm pleased with what I did. I got lazy and painted the whole thing with some of the fleck-tone paint products. My wife thinks it looks like heck! I'm considering building another set of bases and veneering them in some nice wood. I'm listening with interest to what ideas you have. I might incorporate some of them if I choose to start some new construction. I also might get a wild hair and build your project. I'm undecided. I agree with some of the comments that you guys really are a brain trust. ----- Original Message ----- From: Sent: Sunday, January 09, 2000 7:14 PM Subject: Re: Scheu-Subchassis Yes, there are a few of us lunatics out here. 1). I just visited a friend of mine in Northglenn and he has the Clearaudio that costs about $3000.00! I forget what it was called; the something or other Gold. It was amazing. I don't want to spend that kind of money but it was amazing. I like the air that moving coils provide but I've always found them to be tipped up in the high end. Maybe that's why they seem to have so much presence and air. I've been thinking about going back to a moving magnet or various of. Probably just because I'm so cheap, I'll stay around the $500 to $600 dollar mark. Anybody have any suggestions? 2). I agree that the "Flek-Stone" paint looks nice and does hide small errors nicely. My wife want Bubinga or some such amazing wood for the base with the top out of curly maple. I think it would be great looking but expensive and time consuming. I've been looking seriously at a new table saw and am about to take the plunge. 3). I would agree that I probably need to experiment with isolation. In the past to keep things relatively simple I applied lots of mass and skipped the isolation issue. Actually I disagree with your last statement. Further changes in the area of isolation should improve things. Obviously, after a point you get to the point where the changes are small. Sometimes it's hard to decide if a change is better on balance or just different on balance. I find some tweaks to be different and better in some ways but not in all ways. I've been reading the various ideas and contemplating changes. Hope you guys keep up the good work. ----- Original Message ----- From: Jeremy Epstein Sent: Monday, January 10, 2000 8:09 AM Subject: Re: Scheu-Subchassis BBoehler@aol.com wrote: > 2). I agree that the "Flek-Stone" paint looks nice and does hide small > errors nicely. And sounds really good on those Bela Fleck and the Fleck-Tones records! > My wife want Bubinga or some such amazing wood for the base > with the top out of curly maple. I think it would be great looking but > expensive and time consuming. But this is what your wife wants, so ultimately it is what you will end up with. > 3). I would agree that I probably need to experiment with isolation. In which case, ignore your wife's wishes. ;-) ----- Original Message ----- From: Mackris, Thom G. Sent: Monday, January 24, 2000 12:11 PM Subject: RE: Teres Pictures Awsome work, dude !! One thing I was hinting at when Brian spoke of his trashed cantilever was an armboard which would protect the stylus. Chris & I have had preliminary conversations about this. Now, obviously, subchassis/armboard is an area where we're all going to (peacefully) diverge in our opinions, primarily for aesthetic reasons, but here's a thought for your consideration about the approach I plan on taking: I'm envisioning an armboard of the appropriate height (approx 3") which when viewed from the top would look like a large block of material on the right side of the subchassis. It would have female curve which accomodates the platter. There would be perhaps a 1/2" space between the platter and this curve in the armboard. This piece would obviously be quite massive if made out of either MDF or acrylic. The curve primarily is an aesthetic consideration, compared to the appearance of a rectangular block running along the right side of the subchassis. Functionally, the armboard running full length would serve two important purposes for me: (a) it would minimize the amount of air space beneath my precious cantilever/stylus ... protecting it from my cats and myself. (b) it would facilitate manual cueing. On my Merrill, I find myself quite frequently cueing up my records manually. In observing how I do this, I noticed that I steady my hand by curving my little finger and resting it on the front of the plinth (holding the tonearm by the "lift" with my curved index finger). This curved armboard would satisfy this ergonomic (for me) requirement of providing a bracing point for my little finger. The appropriate cutout could be made into the armboard to accomodate an idler pulley 180 degrees from the motor.. This wouldn't take too much mass out of this structure. Cheers, Thom ----- Original Message ----- From: Doc B. To: Thom Mackris / Joan Panzella Sent: Monday, January 31, 2000 5:19 PM Subject: RE: Teres Turntable - Shameless Commerce Division Hey Thom, I'd be interested, but I am so goddamn busy ( it is 4 p.m. and I have been answering e-mail since 9 a.m.)That I will probably have to pass. But I wanted to throw out an interesting idea I've been approached with recently, for the plinth. I have been talking to someone who works with molded polymer concrete, basically pure silica sand in a foamed epoxy mixture. This guy used to produce a speaker cabinet using it, called the Palantier (sp?), and he is doing a set of wood veneer covered Straight 8 cabinets out of it. Might be just the ticket for a TT base, it can be finished in all sorts of ways, including wood veneer, and he says it totally whups Corian and acrylic as a cabinet material. Doc B. ----- Original Message ----- From: jhlane To: Thom Mackris / Joan Panzella Sent: Tuesday, February 01, 2000 3:18 AM Subject: Re: Teres: Subchassis & Armboard Hi friends, I feel a bid presumptious in posting right off like this, but here goes. By the way, sincerest thanks for being included in the list... Somewhere in my pile of misc related paperwork, I have a sheet on casting compounds. These are materials of varying properties used by folks in the biz of making prototypes of parts to be ultimately cast from iron or something. This stuff is some sort of polymer but is filled with metal; lead, iron, etc. I still have a plan to fashion pure, round Tractrix horns for small compression drivers like the Altec 8xx and 9xx series of a particularly dense breed of this stuff that is filled to a very large percentage with iron. If shrinks a tiny percentage, making it dimensionally stable enough, I think, for a 'table base. Probably sonically dead as anything. Dose this sound useful? I can post details within the week if my filing cabinet just cooperates. Thanks again - looking forward to selling the Linn... Best, Jon Lane ----- Original Message ----- From: Schei, Kenneth Sent: Tuesday, February 01, 2000 7:28 AM Subject: RE: Teres: Subchassis & Armboard I like that idea. I've thought about using the same concept to cast fronts for speaker cabinets. For a TT plinth, a carefully made mold wouldn't be any harder than crafting the plinth from MDF, but could be used to cast multiple plinths. Accurate holes for the bearing, etc. can be formed by wood dowels of the right diameter glued or screwed in the proper places in the form. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Schei, Kenneth Sent: Tuesday, February 01, 2000 7:34 AM Subject: RE: Teres: Subchassis & Armboard Jon: Welcome aboard and thanks for the good ideas. Can we formulate these casting compounds so that the finished product is aesthetically pleasing and needs no additional finishing, other than polishing? That would require a carefully finished mold but it would be worth the effort if we were doing multiple plinths from one mold. I think it would be cool if we could have a base that looks like granite or something in a pleasing color or shade. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Igor Kuznetsoff Sent: Tuesday, February 01, 2000 1:41 PM Subject: RE: Teres: Subchassis & Armboard Jon, Welcome, and good opening ! Do all of these polymers come pre-loaded with aditives, or can the resins be mixed custom? Definitely of interst, the whole list & whatever specs may be available! Igor ----- Original Message ----- From: phclark Sent: Tuesday, February 01, 2000 6:17 PM Subject: Re: Teres: Subchassis & Armboard I've been pondering various mechanical aspects of all this for a little bit. An interim thought-solution to the base/plinth/fundament problem I came up with was to use a machinists' surface plate. Advantages abound: 1. they're cheap 1a. they have no materials investigation/application and fabrication cost 2. they're reliably flat 3. they come in a variety of sizes and therefore weights 4. they have stands already fabricated for them (though the stands cost as much as the surface plate) 5. they come in spouse maddening pink or audiophile approved black Weight may be problematic for some. I'm graced with concrete slab floors, so once one of these 55 pound (12" x 12" x 4") and up (way up) thangs is placed, it'll be there for the duration. Might want to put clearance lites on it, tho, wouldn't want to stumble into one in the dark... Peter Clark ----- Original Message ----- From: Sent: Tuesday, February 01, 2000 6:49 PM Subject: Re: Teres: Subchassis & Armboard In a message dated 02/01/2000 8: I've been pondering various mechanical aspects of all this for a little bit. > An interim thought-solution to the base/plinth/fundament problem I came up > with was to use a machinists' surface plate. Advantages abound: Another: most monument companies have headstones with incorrect names on them. If you are in a small town, they will likely give them to you...they have to pay to have them hauled away. Big town companies seem to work differently, so go to the hustings. These places will usually polish the back for about $25, if it isn't smooth enough to suit you. The local company gave me granite for my spindle plinth and for my motor plinth. they are charging to cut the (irregular) block and polish the top surfaces, and to drill the hole for the spindle. Maybe $35 total, so cheap. this is goung to be a real "Flintstones turntable", so called by the salesman at the monument company. For me, the Teres is a backup in case this Rekokut Retro doesn't work out :-) Cheers/Don Carron Rockford TN USA ----- Original Message ----- From: Alex Mitaru Sent: Tuesday, February 01, 2000 6:47 PM Subject: Re: Teres: Subchassis & Armboard I thought about a machinists surface plate, but the only place I found them has only 12" x 18" X 4" at 90lbs and this is a tad small, we want at least 1" around the platter so it should be 14", what do you think?...next size up was 18" X 24" x 4" at 200lbs and that is obviously too big and heavy...plus we'll need a hole for the bearing and some way to mount the arm...but I do like the idea, if we can find the right size...and yes, they are cheap, the 12" x 18" x 4" was around $50... alex ----- Original Message ----- From: jhlane Sent: Tuesday, February 01, 2000 7:27 PM Subject: Re: Teres: Subchassis & Armboard I've been thinking over my suggestion earlier of looking into casting compounds and come to a similar conclusion: Precision casting is absolutely no simple task, and the trial and error aspects are daunting. On the other hand, surface plates are a known material and technology, readily available, nicely finished, variable sizes and weights, and serve audiophile ends. Respectfully suggest the project managers consider researching a just a bit - perhaps no further than the local tool & die guys of whom Denver must have its fair share... Jon Lane ----- Original Message ----- From: jhlane Sent: Tuesday, February 01, 2000 7:38 PM Subject: Re: Teres: Subchassis & Armboard Another local source for really elegant 'table underpinnings might be Room & Board, a furniture store with a number of local outlets, including Minneapolis, and even one in Denver. http://www.roomandboard.com Catalogs free for the asking. For not a lot of money (at least in furniture circles) these guys offer some very nice console-, end-, coffee-, and dining-table size products based on polished granite, hardwood, or heavy plate glass tops on beefy welded steel bases. You picks yer top size and then picks yer base dimensions and... With some pointed feet, a bit of sand-filling of the base legs and some judicious damping of the underside of the top (or using a two-top sandwich), one could conceivably fashion an actual 'table stand (or base itself) with actual spousal approval ratings of an acceptably high magnitude. Jon Lane ----- Original Message ----- From: jhlane Sent: Tuesday, February 01, 2000 7:42 PM Subject: Re: Teres: Subchassis & Armboard > Do all of these > polymers come pre-loaded with aditives, or can the > resins be mixed custom? Definitely of interst, the > whole list & whatever specs may be available! Still looking for the specs, but I recall they're preloaded. I further recall a choice of a variety of filling agents from powered alum to iron. And a variety of selectable shrinkages and machinability indexes. But the work to make this feasible will still be daunting - presumably we don't want to have to get into precision casting. Would be helpful if the machinists and engineers on the list would expand on that topic. Hope I haven't brought up a dead end... Jon Lane ----- Original Message ----- From: phclark Sent: Tuesday, February 01, 2000 9:59 PM Subject: Re: Teres: Subchassis & Armboard Airgas Direct Industrial, Rutland Tool Division http://www.rutlandtool.com They have a fascinating catalogue for someone not in the biz. The hardcopy catalogue can also function as the Sears cat of yore... Peter ----- Original Message ----- From: Sent: Tuesday, February 01, 2000 11:04 PM Subject: Re: Teres-New Member Update Isolation and subchassis. I tend to think that a true 'hung' ie suspended subchassis is more elegant than a 'sprung' ie AR/ Thorens/ Linn etc one. But, A rigid shelf, separate sand box and then some bladders and then the TT, ought to beat just about any affordable TT, with its own supension or not, but on its own. Yeah I don't mean Goldmunds etc. Why? Well I've built up a lot of experience with these sprung jobs, setting them up, resetting them up, ringing up clients every 6-12 months to arrange another tweak-up etc etc etc .......... . The other (NTH American) kind are as rare as rocking horse dung out here. And I own two TD 150's! I think I can honestly say that setting up any 'sprung' TT, is like being Sysiphus! That is, without a levelling jig (like Linn made), that holds the TT and lets you work from underneath easily, and LBNL an earth leakage breaker . Sets of three matching tube spanners, one set for each size of nut, (nylock nuts) are a big help too. I love the satisfaction when this comes right, but I do tend now put it off re my own TT for too long. I begin to think that when acceptable results are available via other engineering paths why bother? Several skinned cats lying around. I am firmly convinced that 'sprung' TT's get more quickly out of wack and with clamp use it's worse. If I had really deep pockets I'd get me a TD 124 or an SP10, overhaul it, stick my 'Smee' on it, and onto the DIY bladders above the sand box, which are both in train chez nous. WTS. And with the Sp 10 I'd only need my cotton gloves and talcum powder in a plastic box for all my 'clients' and 'close friends' aka those who want their 'sprungs' done for free. Tim B ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, February 02, 2000 12:49 AM Subject: Re: Teres: Subchassis & Armboard Peter, Jon, I plan for my initial trials to be built with a constrained layer MDF/lead/MDF sandwich laminated with Swedac vibration-damping glue from Soundown Acoustics Corp in Massachusetts (already on hand/they call the glue "DG-5"). The lead is available in sheets from X-Ray supply houses. This is the most flexible & inexpensive medium that I can easily work & modify without major difficulties or special machining, and therefore perfect for (changeable) experimentation. I am, nevertheless, always curious about any new possibilities & materials. There is a local supplier of all sorts of beautiful polished stones that are sold for fancy countertops & a # of other app's, and I have been tempted to use them for a variety of audio app's. They even offer pre-made stone pedestals in various sizes and stones which could be matched cosmetically to, say, a polished stone plinth. If I ever break one of these countertops during an install, and don't commit hara-kiri over this, that's exactly what will happen to the pieces. Making molds is a bit of work, but doesn't necessarily frighten me, as some years back (as in quite a few) I was the Vice President of a small specialty skateboard manufactury, and designed a few molds & built the prototypes & some of our molds by hand. I don't suggest this for one-offs. Mold making justifies itself in multiple *re*-productions. Perhaps I simply missed it, but I don't seem to have noticed what, exactly, these machinist's plates are made of (?). Of what could they be made of, or what reason would they have, for coming in "maddening pink" ? Igor ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, February 02, 2000 1:30 AM Subject: Re: Teres: Subchassis & Armboard That explains the weight and pink color, which I've seen. Pink / gray, anyway. Granite can also come (from a countertops maker) in a fabulous *blue*/gray, with a variety of veining patterns possible, depending on the quarry it comes from. Smallish pieces, such as we would use, aren't very expensive in *whatever* size one specifies from these countertops makers, and they are much easier to find than machinist's suppliers as stone countertops are "all the rage" in kitchen remodeling during the last almost decade, and all the fanciest kitchens just "must have them" (don't tell your wives, that's dangerous!). There are always cutoffs left from large slabs, broken or damaged ones, and, sometimes, even, returned ones from hyper-demanding customers. And *that's* being fussy, at $2-10,000 for a huge counter sized slab! The stone(s) come in an amazing variety of vein patterns and colors. The suppliers can cut, drill, shape edges, and polish the stone to a variety of glosses. Igor ----- Original Message ----- From: Allen Wright Sent: Wednesday, February 02, 2000 3:50 AM Subject: Re: Teres: Subchassis & Armboard Peter wrote, >>>to use a machinists' surface plate. Advantages abound!<<< Great idea - granite is said to be the least reasonant of the heavy stones, the high mass is essential IME and allows an effective air suspension to be used beneath - also essential! Jon wrote: >>>Another local source for really elegant 'table underpinnings might be Room & Board, a furniture store with a number of local outlets, including Minneapolis, and even one in Denver. http://www.roomandboard.com Catalogs free for the asking<<< OK for those in the US but not so easy over here - but there are enough tool shops and grave stone places - kinda international, both... Allen (VSE) ----- Original Message ----- From: Gary Bronner Sent: Wednesday, February 02, 2000 4:34 AM Subject: Re: Teres: Subchassis & Armboard Hello to all from a new member of the list. First let me express my thanks for the invitation to new comers and my admiration for the great work you have already done. Regarding the subchasssis, a little over a year ago I actually assembled a Scheu turntable and I built the subchassis and armboard out of stone. The size of the subchassis is 20 inches x 16 inchs. I had it built out of 3/4 inch (19mm) stone. I had them put a 3/4 lip around the front and sides so that the subchassis appears to be 1 1/2 inches thick. I then cut a piece of 3/4 inch MDF and bonded this to the stone. I looked at both marble and slate. Without the MDF, the marble rings unacceptably, but with the MDF bonded I couldn't see much difference between them. The MDF/stone combination is very dead. I ended up using slate, but marble or other stones gives you more choices in terms of appearance and is much easier to find. For the scheu turntable I also needed a raised platform to mount the tonearm to get it to the right height. A 1 inch piece of stone about 3inches x 4 inches was needed. Making this platform out of stone forces you to dedicate the subchassis to a particular tonearm, but it would be possible to cut bigger holes in the subchassis and mount different tonearm pieces to the MDF for those wanting to swap tonearms. A local shop that specializes in stone work for kitchens and bathrooms did all the work of cutting the stone, rounding the edges, cutting and gluing the front/side edge pieces and tonearm platform, and drilling mounting holes for bearing, motor, and tonearm for about $200. By the way, before trying the stone subchassis, I tried making it out of solid wood. I'd heard good things about beech, I made a subchassis the same size out of some scrap beech boards I found at the local lumber yard. The boards were 3/4 inch and I doubled them up to make a 1 1/2 inch thick subchassis. The entire subchassis looked beautiful but was very resonant and I didn't find it to be a good solution. ---Gary ----- Original Message ----- From: Stewart Ono Sent: Wednesday, February 02, 2000 4:40 AM Subject: Re: Teres: Granite as a subchassis Granite is favored in the machinists' trade because the high quartz content makes it dimensionally very stable over a wide range of temperature. I'm not so sure about the effect of granite for audio (not meaning to rain on anyone's parade). I've experimented with shelving made of marble, granite, slate, and other materials. Granite has the effect of imparting a high frequency edge to the sound. Actually, in my experience MDF has sounded the best, and I believe a lamination of lead and MDF may be the best and most neutral sounding. This was based on some experimentation done about a decade ago. While many of you may scoff at things like the Shun Mook discs and the Shakti Stones, they do work in a subtle yet audible way. An x-ray of them, followed by a cutting open of the devices, reveals a quantity of crystals within. The Shun Mook looks either to be a ruby or amethyst and the Shaktis use quartz. The theory is simple: quartz, tourmaline, and a few other crystals are piezo electric and this is usually interpreted to mean that under mechanical pressure, quartz develops an electrical signal. The inverse is also true: under a strong EMI/RFI field, quartz will develop mechanical motion. Ben Piazza, the designer of the Shaktis, claims that the mechanical conversion of the EMI fields by the quartz reduces the EMI field effects upon the adjacent circuitry. I conversed with a Phd in EE from MIT about this and he laughed saying that the reduction in the field would be extremely small and may be extremely difficult to measure, but he could definitely hear the effect when demonstrated on my system. Piazza has a white paper available and claims that as partial proof, the Shaktis measure consistently about a degree above ambient temperature as an indication of the proof of effectiveness. He has other proof in measurable reduction in RF from some unnamed lab (Yeah, I know the replies of the skeptics). I believe this is why granite is poor choice for good sound, despite it's otherwise excellent mechanical properties. For the inquiring minds, try this experiment. Take a small piece of quartz, say 1/4 inch in diameter or smaller (>6mm). Place above your motor pulley on your TT. For a Linn or SOTA, just throw it in the pulley well. For a VPI use a bit of blue tack to adhere it to the pulley. The sound will be noticeably better, clearer and more dynamic. Small shards on your coupling caps seem to work extremely well as well as placing larger pieces upon your power transformers. Too much crystals, and I say this as a collector of mineral specimens, and the system becomes very hard sounding. The crystals have to be able to move, incidentally, in order for the effect to be heard. The transformation of the EMI field into mechanical energy cannot otherwise take place. Yeah, I know it sounds like I've been a bit overexposed to the full moon, but try it before condemning it. In the case of a granite shelf or plinth, I believe the high mass would make unlikely to respond to the EMI/RFI it absorbs. Stu ----- Original Message ----- From: Schei, Kenneth Sent: Wednesday, February 02, 2000 7:46 AM Subject: RE: Teres: Subchassis & Armboard The only really hard thing about "precision casting" is making a decent mold. The mold needs to be designed so that it releases the finished casting satisfactorily and needs to be finished well inside so the outside of the finished casting is attractive. Using a polymer that has a very slight shrink will also help with the mold release. Special spray-on mold release agents also are available, although PAM has been used. The hole for the bearing can be formed by a dowel which would be fastened to the mold with a screw, so it could be removed with the finished casting and then removed from the casting. Building the mold would require woodworking proficiency and tools that at least several of us have, and multiple finished plinths could be produced. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Schei, Kenneth Sent: Wednesday, February 02, 2000 7:53 AM Subject: RE: Teres: Subchassis & Armboard Igor: I really like your plinth idea with MDF and lead. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Schei, Kenneth Sent: Wednesday, February 02, 2000 7:56 AM Subject: RE: Teres: Subchassis & Armboard If we were to use something like granite or an old Y2K tombstone, I'm a bit intimidated about how we would drill an accurate hole for the bearing, as well as mounting other items like the motor, idlers, etc. Ken ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, February 02, 2000 2:05 PM Subject: RE: Teres: Subchassis & Armboard Ken, Thanks. I see Stewart Ono also agrees, though I didn't notice any reference to my post of last night. I consider stone a *cosmetic* material. Massive, yes, but *resonant*. It would have to be bonded to something like MDF, as per Gary Bronner's post that I also noticed today to make it work well. Although my previous post suggested that I would only use this construction initially, I actually fully expect the final plinth(s) to be made the same way, but they will probably be evolved refinements of the first ones, unless I hit everything right on with the first try, as happens more often than not. If you have not used Swedac/DG-5, be advised that it dries very slowly, especially when constrained on one side (or more) by a non-absorbent (the lead) material. It may well take as much as most of a week to set up completely. You can use this construct after only a day or two, but, sonically, it will keep changing until completely set, just so you know. It is also rather pricey, as glues go, but would probably be the very best for the purpose. I can try to find an address for the suplier if you want. Igor ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, February 02, 2000 2:17 PM Subject: Re: Teres: Subchassis & Armboard Hi, Gary, You are quite right about solid wood being quite resonant. The denser, the more resonant generally. Ditto the stone, which should never be used alone, as you observe. As solid woods go, I have found that Cedar and Redwood, both very soft woods (almost unusably so for some app's), are quite good. Please be advised that both of these woods should *never* be worked without the use of a dust mask, as they are allergenic to the human body, and should not be allowed into your lungs, as long-time woodworkers have discovered. The best possible option for non resonance, neutrality, and ease of working is MDF/lead/MDF, bonded with Swedac. Igor ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, February 02, 2000 2:29 PM Subject: Re: Teres: Subchassis & Armboard Allen, Don't they use Stone slabs for countertops where you are? The suppliers of these can do all the operations needed to any spec. Stone should not be used alone without bonding to something less resonant (which could go underneath, for instance), see Gary Bronner's post. I certainly agree with you about the air suspension. I've crusading for the use of small bicycle (2.25 or 2.45 x 12") inner tubes, which are made of butyl rubber, just like the "lossy" rubber surrounds on speaker drivers, for six or seven years now. They are not the only air bladders that can be used, but they seem to be the best & most easily available. Igor ----- Original Message ----- From: Sent: Wednesday, February 02, 2000 4:23 PM Subject: Re: Teres: Subchassis & Armboard In a message dated 02/02/2000 9: If we were to use something like granite or an old Y2K tombstone, I'm a bit > intimidated about how we would drill an accurate hole for the bearing, as > well as mounting other items like the motor, idlers, etc. First, half of the stones are marble, with 1/3 the hardness of, and a lower resonance than granite...prettier, too. Pick one of marble. Second, the stone places will cut or sandblast holes cheaply, and finally, we can drill screw holes with masonry drills, and install shields. Cheers/Don Carron ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, February 03, 2000 1:04 AM Subject: RE: RE: Teres: Subchassis & Armboard Guys, I should take this opportunity to mention that regardless of how well the subchassis is designed, the sandbox, in combination with a pneumatic suspension underneath it, will still serve in a superior fashion to block transmission of floor-borne vibration, in addition to its chassis vibration sinking duties. I ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, February 03, 2000 1:15 AM Subject: RE: Teres: Subchassis & Armboard Ken, You are quite correct in thinking that holes drilled in stone, particularly by conventional commercial techniques lack accuracy. I've certainly seen this with countertops! One way to deal with that would be to have the holes drilled oversize. Then, they can be filled with a resin of your choice (as simply as with automotive "Bondo"). After *thorough* hardening (if not, the stuff will make a mess of your toolbits while not machining neatly) you can proceed to make precise holes. Igor ----- Original Message ----- From: phclark To: Teres Sent: Thursday, February 03, 2000 1:51 AM Subject: [teres] Re: Teres: Subchassis & Armboard Might I humbly suggest JB Weld for the task. It's an epoxy (I think, it's a two part) that will set up in 24 hours hard and stable enough to be machined. Cheap, easy to work with and available in every village. Amazing stuff. JB Weld has collateral pluses in that it's also conductive. This means that nasty, pitted old Dyna ST70 chassis that you've wanted to rehab can now be filled and sanded smooth after being "bondo-ed" with JB Weld and you can have it powder coated!!!! Tres chic, tres boss. Boy, the obstacles are just melting away, aren't they? Peter C ----- Original Message ----- From: Igor Kuznetsoff Sent: Sunday, January 09, 2000 1:49 AM Subject: Sandbox (& motor) [snip ] Also- thought of a neat tweak for our sandboxes: if we do separate subchassis (good idea) for the platter/arm & idlers to make sure that no bearing noise transfers, we can improve isolation at the sand by sinking foam rubber sleeves into the sand (mix) under the cones attached to the subchassis the idlers are on. The motor, as discussed, will have its own section of the sandbox, and that will keep that well separated, but both subchassis will be achored to the same volume of sand on the other side. This would probably already be better than any other rig I know of, but it would take very little effort or cost to improve even further on that. What I have in mind is to either make ~3-4"D sleeves out of ~1/2" thick foam rubber (such as closed cell, black, neoprene) of medium to fairly dense consistency, & of a height calculated to be just short of the sand's surface (so they are *just* buried, for cosmetics); or simply use common foam rubber beer/soft drink insulators. The drink insulators (the sort you can get anywhere, usually with either advertising or cute sayings/jokes on them even come with bottoms (with a small hole) on them, and only need to be trimmed in height. These can be layed in on the sandbox bottom prior to filling with sand (centered carefully where the cones will go). After filling, they will create a hidden, isolated, pocket of sand that each cone will sit on, and will *guarantee* that no idler noise can travel through the sand and over to the cones the platter/arm subchassis is sitting on. I