Polivoks CV mod problem

runewerner · Joined: May 05, 2011 Posts: 2 Location: Denmark

Hello,

I'm attempting to mod my Polivoks with CV/gate. I've followed these instructions: http://technopop.info/polyvox/index.htm
And it's working... almost!
The gate part is working on some octaves, but the tuning is behaving strange. I think I might be using the wrong IC.
On the diagram, it's says you're supposed to use a 4558. I'm a tech novice, so when my local electronics-dealer told me I could use a M63AJ/LM393N instead, I trusted him (he didn't have the 4558). At this point, I just don't think he was right Smile

Any of you guys know which one's the right one to use? If not the 4558, then maybe an alternative, which doesn't requires modifications to the PCB.

Hope you are able to help,

Regards,
Rune

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diablojoy · Posted: Thu May 05, 2011 2:27 pm Post subject:

lm393 is a dedicated comparator chip so yes i think it is wrong
you need an op amp in there, 4558's are not hard to get though
you could try a TL072 instead
edit : i think that should work ok but not sure if you would need to change any resistor values around it to get the cct to behave as it should

runewerner · Joined: May 05, 2011 Posts: 2 Location: Denmark

Thanks a lot!

I'll try that!