Hi there!
I think I would like my quad vca mixer to have exponential vcas.
Maybe mod 2 channels out of 4, something like that.
Am I right to think I can just cut the trace from pin 3 to 4 and jump pint5 to 3 and the vca will behave exponentially?
hmmmmmmmmmmm lets see , maybe? there could be something possibly missing . Let me look deeper and get back
Look at the datasheet here :
http://www.alfarzpp.lv/eng/sc/AS3360.pdf
and compare with the schematics of the QuadVCA here :
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@eric This design seems a bit strange to me. Specifically the D1 on pin 6.
Firstly CV needs to be conditioned to be 0 to 1.7 V, and you could cut off the negative side by putting D1 on pin 5. But now it seems to bias the signal side. Is there a mistake? Or I’m not seeing something?
I didn’t analyse that schematics too closely as I’m building from Sam’s PCBs…
But I agree, that diode looks suspicious on that pin !
That’s a 2 V Zener diode, it’ll conduct above +2 V and below -1 V. The CV on pin 5 is supposed to be 0 to +2 V (absolute maximum -2 V to 2.5 V). I agree, it looks like it’s on the wrong pin. Is it on pin 5 on the actual PCB?
I had time to check the #1181 Dual VCA PCB, and…
The zener diodes go to pins 6 and 9, the signal inputs of the 3360, not the CV inputs !!!
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So, @lookmumnocomputer, is that intentional? If so, how does it work?
This came just in time, as #1181 is in my pipeline for this week-end !
I guess I’ll have to bodge the diodes in.
Doesn’t look too complicated on #1181.
I don’t know how easy it will be on #1183…
Between 1.6 V and 1.8 V. The block and connection diagram says 0 to +2 V on that pin. The absolute maximum rating is -2 V to +2.5 V.
So the zener (when on the correct pin!) enforces a safe range; the useful range is smaller.
Anyone heard from @lookmumnocomputer on this apparent error?
Is this the same diode we were talking about here?
Yeah, looks like it is.
But I have trouble reconciling that with @eric’s seeing it on their PCB. Unless they got theirs about eight months ago.
Mine is a #1181 (Dual VCA), and I bought it end of november IIRC…
I have an early one, do i just clip out the diode? Only just got it working last week after discovering the CV input resistor was magnitude of 1000 out!