Transcendent Polysynth

[Tony Allgood]

Hello all.

Looking at the references to the transcendent 2000 monosynth, I wondered if
any of you had built the polysynth designed by Tim Orr. This was published
in about 1980/1 in ETI magazine. The standard unit had a fairly
straightforward synth architecture, ie. 2 VCOs, 12dB LP VCF, 2 EGs and a
VCA. The VCOs and EGs were CEM but everything else was opamps and
discretes.

Each voice was on one PCB which makes it great for building up modular
monsters or simple monosynths. I use four of the voice cards with an
appropiate power supply for a polysynth, driven from a Design Labs PROLOGUE
midi-CV box. It sounds very nice, especially with each VCO having a
separate LFO for PWM and vibrato. The filters are a bit peaky mind, not
that smooth compared with my Rogue clone. And boy does the output drive my
speakers crazy when the Q is full up. The VCF is based around two halves of
LM13600. Do these sound different to a LM13700? 

I use another two voice boards in my modular set up. They form the heart of
the system. Very useful building blocks indeed. In fact I've hard wired two
of the above filters in series, with a common exponential driver but
separate Q feedback loops. The results are really quite awesome, more acid
than bucket of ripe lemons. These two I drive from a Pro-2 from Kenton. The
pro-2 is a good machine, the prologue, on the other hand, suffers from a
noticeable CV glide on every note change. One to fix when I have the time.

Oh yes, the other great thing about the Tim Orr polysynth, is that it has
no fancy digital hardware for its keyboard interface. Just 74 chips and a
couple of SRAMs. No midi mind, but it can control 1,2,4 or 8 channels of CV
and gate.

So are there any other users of this machine, either whole or in bits like
mine?

TTFN

Tony Allgood