SixTrak 6-Output Modification?

[media at mail1.nai.net]

At 8:24 AM -0700 04/14/98, Fitzhugh, Karl wrote:
>Anyone have any details on the 6-output modification for a SCI SixTrak?
>I've seen mention of it on this list, and elsewhere on the net, but
>can't seem to find any actual details on it. Basically I'm looking for
>plain and simple instructions on how to do it - I'm not exactly an
>expert at this sort of thing!
>Hope someone can help, or point me in the right direction - thanks in
>advance.

Even though this might sound contrary to the spirit of synth-diy, imho, the
right direction would be to moving away from performing such a mod.

The first modification of this type was developed by Christopher "Litho"
Jones.  Perhaps you can still find it at:

http://mcjones-mac.wca.ohio-state.edu/self-oscillator

It basically hacked an output directly from each 3394 chip.  Not only does
this rely dangerously on the input impedance of an external device, it
doesn't jive with the little I know about CEM 3394's.  As far as I know,
the output is expressed as a current not a voltage.

A much better modification was later developed by some guy whose address
was elizalde at internetconnect.net.  Word on the street was that he used to
work for Sequential Circuits.  Try pointing your browser to:

http://www.geocities.com/SoHo/8047/sixtrak.htm

This addressed the impedance levels and autotuning noise ignored by the
Litho mods.  Otoh, it also required building another PCB and separate power
supply!!

I own a Six Trak myself.  It's a nice synth, but do not think it is worth
all of the work and risk involved in adding an individual output for each
voice.  The sound of a lone 3394 isn't that amazing.  I find that I mostly
use my Six Trak in stack or unison mode.

There is no easy way to add separate outs to a Six Trak -- the simple way
is dangerous and the safe way is complicated.   Remember, this is an old
digitally  controlled synth.  SCI and Curtis both went out of business and
it is difficult to get parts if something goes wrong.

PEACE OUT :)
MARK