Music Tech DIY • Trying to build Eddy Bergman AS3340 VCO

Hi!

I'm trying to build the AS3340 vco as the Eddy Bergman version,working at +/-12v but I only need the triangle output.
My friend asked me to use the AS3340 chip, to build some for him, and there is no discussion about that. So, I thought, ok, I can leave out much of the circuit:

All circuit tied to PIN 4: NOT BUILT.
External PWM input tied at PIN 5: NOT BUILT.
All SYNC circuit tied to PIN 6: NOT BUILT. (R24, R26, D1, D2, C9, C10)
FM input circuit tied to PIN 13: NOT BUILT.
C8 soft sync IN tied to PIN 9: NOT BUILT.
Sawtooth output at PIN 8: NOT BUILT.

For R23, I replaced from 910R to 680R, as Eddy recommends. I don't know if a 10K to gnd in parallel is necessary... I tried, but no result.. no sound at all...

I hope that UNUSED PINS, are not a problem, to leave them like that... unused.

For C7 I placed a 470 PF Polystirene, as recommended.

Despite all of this, it still does not work. I can't hear any signal output.

I'm using an Arturia Keystep connected to the computer by USB, and the CV PITCH output connected to the 100k resistor V/oct input in the summing node of the AS3340 circuit.

Attached are both my simplest version for +/-12v rails, and below, the original schematic that works at +/-15v.
NOTE: The voltage of the rails is not a problem, as Eddy explains that there are some values adjustments to be made, and it should work fine.

Perhaps I missed some circuitry that should be built...
Or, the unused pins should be terminated some way...

I have built the circuit on a protoboard, and checked every connection several times... maybe I'm getting nervous and missing something...

Thank you for your help!

jay x

Statistics: Posted by jay x — Fri Oct 25, 2024 11:14 am — Replies 2 — Views 63

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