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Paia 9720 vco modulation problem
MUFF WIGGLER Forum Index -> Fractional Rack Modules  
Author Paia 9720 vco modulation problem
Archie64
Hi Chaps, having a problem with my paia - there seems to be a constant frequency modulation on the output of my 9720 vco which starts about two and a half octaves up from my bottom C and gets progressively worse the further up the keyboard I go. I am fairly confident it is not the built in modulation circuit as that gives a significantly different modulation when introduced - it is more of a classic FM sound.
I have another 9720 module in the same rack and the same thing happens to that.
Could it be the power supply? - it is a 12v 3 amp jobby and I have tried it with just the midi2cv8 and the vco module plugged in with the same results.
Any suggestions would be welcome.
ddoyen
Have you tried contacting scott at paia? I know he is on vacation for a few weeks but hes pretty great with troubleshooting.
nikmis
This might be the paia midi2cv circuit. If its the same problem I have, it is high frequency noise on the output of the pitch cv. It is worse the higher the pitch, with higher voltage. The way I deal with it is to put it through a glide/slew circuit. Even at minimal settings with almost no glide, it removes the noise. Is it the same with your PAIA vcos? If you turn up the glide, does it remove it?
Archie64
Hi, this is definitely a power supply problem - I found out the hard way when I accidentally shorted the + and -V to earth and blew the diodes on the main PSU - replaced these and the caps and everything was fine - dont know if this was a problem that had been bubbling away for some time and the short just tipped it over the edge but it certainly helped sort out the exact same problems that you are experiencing plus a nosie problem I was experiencing on the VCA dissapeared too.
Are you using the 12v 3 amp psu from Maplin? one thing I noticed on mine was the blue led on the psu was not lit until the fault was sorted (possible short?)

Hope that helps.

Ray

BTW is it 9700s? - my system is 2x9700s racks plus cv source, sample and hold. passive mixr/splitter and custom voltage attenuator/splitter.
Awesome audioness!
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