 Lets introduce me and my system to you. I'm Andy and I'm a vinyl classical music freak. Now that's enough said about me so now to the system. The Record Deck
I struggled for some years with a record deck atop a stand. Even good stands
are poor when placed on suspended wooden floors, which are common in older
houses in the UK. When we decided to extend the house the second priority
(the first was the kitchen for the wife) was to have the music room extended
and a concrete floor in the extended part. This was a great decision! A
large sand box using dry silver sand (it does not clump nor encourage growth
of plants), 130kg in all, was used as the base for the record deck. Atop
this is a sandwich of two layers of slate epoxyed together (originally
I had used chip board but slate sounds better) - then four Newport Systems
air suspension pucks - then another smaller sand tray then the Michell
Gyro deck. I guess by now you can tell I'm a bit over the top, but more
of that to come! My stand can withstand a fair sized kick without any noticeable
sound coming from the speakers and I regard this as a "key test".
The Pre-amp
The pre-amp is a two box affair. One box houses four transformers, each
250VA, for the HT and heaters configured as a true dual mono unit. The
other box houses the pre-amp proper. Each box is about 10" high, 20" wide
and 19" deep. Construction is MDF with some lead lining. This provides
RF attenuation and deadens the ringing nature of the MDF. I would not use
MDF again. Instead, I would use beech and a constrained layer approach.
Each box is far too heavy - I split my trousers trying to move the power
supply from my desk to the floor!
The Power AmplifiersPower amps are based on a design published in Glass Audio, Volume 1, Number 5, 1993. Recently, they have been rebuilt with a few mods, most of which have also been in GA. Once again, large and heavy construction.The SpeakersThe speakers are ESL63s supported on big stands 18" off the floor. Not the greatest speakers, but I don't know of anything I could live with and maintain a comfortable relationship with my neighbours. |
The deck is fitted with a DC motor, rather than the standard AC one. An
SME arm and a Clear Audio Gamma cartridge finish the vinyl front end. The
DC supply for the Gyro motor comes from a rechargeable battery followed
by two voltage regulator stages. Oddly enough, it is important to have
two voltage regulator stages. I used a 7809 and an LM317. A small adjustable
pot is available for speed adjustment but, to be honest, I don't tweak
it more than once a year.
Circuitry is actually simple, 6 separate HT regulators based on a no feedback
design, 6 HT buffers, 12 heater regulators again using no feedback technology.
Huge numbers of FKP1 caps - about 250 in the pre-amp box!