(Andy with his handiwork)
(Andy with his handiwork)
Quad ESL63s
These are on quite high stands as this makes the image better positioned and
also adds a surprising amount of air to the sound of the system. The little
black box with the wooden top at the base of each ESL63 is the 240 regenerator
which starts with a 60Hz oscillator and via a power amp re-generates the
supply voltage. This makes a huge difference to the sound. Next steps here are
the installation of a direct to 5.25KV supply where the voltage multiplier is
removed! The ESLs themselves have replacement Mills resistors and Multicaps
fitted along with a new EHT multiplier using WIMA FKP1 caps and (most
important) a couple of ferrite beads (single bead Phillips type 3S1) after the
regulator and before the diaphragm.
Power Amps
(No feedback, parallel 6550's in push pull monoblocks)
The power amps are very much as per the Glass Audio expect that I rebuilt them to increase the size of the transformers see GA 1/1993 and to have a wooden case to reduce the resonance associated with metal cases. I also removed the feedback and changed the front end as per later articles in GA see 6/1998 Heater care and feeding & 6/1999 Analysing the Hedge Voltage amplifier.
Pre-Amp
(The preamp and powersupply. Can you say overkill!)
Well this is a whole story in itself! The power supply is totally dual mono with 4 transformers each about 250VA. One supplies the HT for each channel and the other the heaters. Each tube is fed from its own winding on the transformer via rectifiers and regulators, as you say a bit over the top. PP caps by the ton for the supplies. The box is lead lined to reduce vibration. Now for the preamp proper. It is fed by two umbilicals. All heater and HT wire is Kimber. We auditioned lots of different wire types even for the heaters and Kimber is the best we tried although tri-rated switchgear wire came a close second and its dirt cheap. Interestingly enough any plated wire sounds bad to our ears and silver is a no-no. The circuit is fairly simple a Mu follower front end, passive RIAA, resistor load second stage and Mu output stage. Tubes used are 12AX7(ECC83) 5965, 6072 and 6SN7. All tubes have their own regulators and HT buffers all FET NO feedback designs (article upcoming in Audio Xpress). It's a radically different approach. All PCBs are copper clad teflon (crucial if you use fibreglass then its severely bad news). Casework yet again lead lined in order to reduce the microphony (weighs in at about 60lbs). Once again auditioning showed that the difference between using epoxy glue for the lead wood interface was audible when compared with contact adhesives reasoning is simple contact adhesives make contact very seldom! Cheap bicycle inner tubes are the air suspension system this time.
(A view of the preamp from the top)
(From the bottom. Note the stepped attenuators and lots of polproplyne caps)
Turntable
The turntable is s straight Gyrodec with a DC motor supplied a battery and a two stage regulator. Once again tests having showed that a two stage regulator was greatly preferable over a single stage and a lead acid battery likewise over the utility supply and transformer etc. The Gyro sits in a sand pit (silver sand sounds better than builders sand as it does not clump) which rests on 4 air pucks (Barry controls - available from Newport) which rests on two sheets of epoxy glued slate and hence on a sand box filled with approx 300 lbs of silver sand on a concrete floor. Once again tests showed that the slate was audibly superior to chip board!!
The arm is an SME 5 and the cartridge is a Clear Audio Signature.
That's about all. Virtually every change ever undertaken in the system is tested blind by friends! You may not believe it but its true.