JH-4 VCA schematics available

[Haible Juergen]

I have just made my first scan now! Seems to work, though the quality
is worse than the pictures Kevin scanned for me. But I am sure with a
little practice I can improove the quality.
I won't mail it to the list, but if someone wants to see it, just tell
me by
private email, so I can send you a copy. I have also mailed it to Kevin,
so it may appear on Synthfool web site as well after some time.

Short circuit description:

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This VCA system is part of my JH-4 PolySynth.
The first four differential pairs form four VCAs in parallel to scan
different filter
outputs. So you can sweep thru 2pole-LP, 2pole-Notch, 2pole-HP, 2pole-BP
and 4pole-LP continously with a single control voltage.
The next two differential pairs are used as a stereo VCA. For Panorama
Modulation, the current distribution of these two pairs is controlled by
a third differential pair. Panorama Modulation Amount is controlled by a
CA3080.
The VCA can be modulated by two different ENV generators. Which one is
chosen, and how large the amount of modulation is (i.e. output volume),
is contrlled by a single CV, and using two halves of a LM13700.
The last two differential pairs work with constant current and emitter
degradation.
They act as class A symmetrical buffers / output drivers.
The whole circuit is tested. I cannot guarantee that the schematic
diagram is free
of errors, however. It is important that the transistors of each
differential pair
are matched for vbe.
As with all my circuits, you may rebuild it freely for private,
non-commercial use.
If you want to copy and redistribute schematics, please tell me so, and
keep a
reference to the source.
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JH.