Sound Techniques Studio/Desks, Chelsea - UPDATE

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Still in touch with Geoff Frost...
He has updated his site...

BTW - there are piccies and a description of what would become the Trident desks (I think)

"Over the coming months, I shall publish the history, descriptions, pictures, technical data and provide as much technical support as I can - so you can get these desks working again. Many parts are still available, or I maybe able to help you find similar items. Please feel free to ask any (polite!) questions. Geoff Frost "

Look at the circuit boards.. Check out the Wima caps

The first 'range' of mixers were called the 'A' range. (I assumed we'd then go onto making a 'B' range, and so on. In the event, the next series of desks were called 'System 12'.)

I had toyed with the idea of a valve (tube) mixer, but I didn't like the thought of making lots of metal boxes! There was only one type of amplifier used, and each had transformer output. I am a great believer in the use of transformers: they neatly avoid ground loops, the signal can be sent over some distance - the low impedance and balanced output helping to keep out noise. However, the most significant advantage is that if you let the transformer go into distortion first in the chain, the waveform will be smoothed off, rather than a straight clip. The distortion produced in much more acceptable to the human ear.

To save money, both the mic and line amps were exactly the same. The very early printed circuit boards were cheap paxolin, with the copper 'soldered over' the copper tongues where they plugged into slots on the console.

Four silicon transistor were used (2 x BC109, 2N697 & 2N1132), along with an off board transformer. They ran off a single 12 volt supply. (Later increased to 15 volts to provide more headroom - +24dbm.)

You lucky people!!


More info from Geoff - this afternoon
Hi Simon,

Fine. Just started a new page on circuits. (See link on home page.)


Schematics and Block diagrams now being posted!!!
System 12 TTL monitor switching
System 12 block diagram
System 12 EQ curves


Grounding techniques used in Chelsea Studios


More PCBs from the A Range..
Inclusing the Copper Trace Side


More updates....

A restoration of an old desk
(Interesting the quote...
The plan is to fully restore it to it's original performance, and then re-install it in a famous 'retro' studio in London.

much more stuff
Internals of constant impredance faders by Painton

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