[sdiy] patching polys(ESQ), newbie question, electronic kits

[harrybissell]

juju punky wrote:

Hi juju  (nice nic)

> Florian Anwander recently commented on Analogue Heaven about the
> possiblility of adding exciter or distortion circuit to the CEM patch
> points. I think this is an excellent idea. In fact, a small amplifier
> circuit with which to overdrive the VCF a little might be sufficient,
> but I think this would require patching in before the CEM 3379 rather
> than with CEM's insert pointed out by Florian - as he said, it's the
> oscillators that need work, not so much the filters.
>
> So, if someoone like myself were to integrate something like this
> fully into the synth, you'd have to consider that you need a circuit
> that's small, low-cost easy to duplicate (for each voice), and not
> terribly time-consuming. Which leads me to the idea of.using one of
> the kits like I find here:
>
> http://store.qkits.com/category.cfm/AUDIO
>
> Not only a wide assortment of small amplifiers, but tone controls,
> bass boost(! pre-filter bass boosting?!?!?) and all sorts of things
> that may be perfect for a layperson like myself to patch into audio
> chains.
>
> Again, I'm no electronics engineer. Would incorporating a set of, say,
> 2W amps, or perhaps a tone control (I realize they aren't selling Neve
> EQ clones) from a supplier like this, somehow isolated, into the
> signal path of a DCO polysynth, degrade the signal quality beyond
> being worthy of any potential benefit? Even if I were to build a
> breakout box for the additional circuitry, would the RF introduced by
> new wires, soldering, etc. render this a bad idea?

Depends on how you do it. With good wiring etc it need not degrade
the quality. OTOH if you are not proficient (or better still, patient and
perseverent :^) you should not try a major mod.

The "2W" amp will buy you nothing... you don't need or want power at that
point. Most of the Qkits will not be what you need either. Simply changing

the tone control before a filter will have little effect... easier to do
it after the
filter.

I'd suggest studying some guitar effect circuits, especially distortions.
The tough
part will be making it so you can bypass the circuit when you don't need
it.

> Also, I realize there are double and perhaps even triple
> potentiometers out there, but if one were to want to gang 4-8
> amplifier circuits to the same gain control, what would be the best
> and/or cheapest and/or most hassle-free way of going about it?

er... VOLTAGE CONTROL :^P

You design or modify a circuit that can do what you want and allows you to

control the parameters with a control voltage and a single pot.

I'd think that a good way to go might be to make a VCA using an LM13600 /
13700 / CA3080 / NE5517 / CA3280.... then fix it so that you can get
distortion or overdrive with that.

There is a diode input all these except the 3080.  If you source a current
into
the diode bias... it will be quite linear. If you don't, it is easy to
overdrive the inputs
and get distortion.  If you are clever with the values, you could use one
transistor
on each one as a multi-gang switch and select either clean or dirty.

I read a report that Tangerine Dream once hooked up the voices of a
Prophet V
through five separate "Big Muff II" fuzzboxes...  inspiring ???

Making a unit to modify a polysynth is in effect (pun intended - groan :^)

making a new polysynth.  It will take a lot of parts, time, investment,
and some
risk if you fvck up big time....

H^) harry