[sdiy] Roland JX-3p vca - noise

[Oakley Sound]

It's probably a poor connection somewhere since it goes away when you 
change the volume levels. But if not, one other place to look is the 
output mute circuit. TR7 and TR8 being the mute transistors. These can 
go bad and produce some odd distortion effects.

Virtually every JP-6, which has a similar circuit to the JX-3P, I have 
seen has poorly output mute transistors. But that tends to manifest 
itself as an overdriven sort of sound when you have the VCA level and 
volume up. I sometimes see a comment about the JP-6 having some sort of 
deliberate overdrive capability but it's usually just a bad output mute 
circuit. Take the mute circuit out and it's as clean as a whistle.

Since the output of the JX-3P is stereo - does it crackle identically on 
both sides? If so the problem is possibly before or in the chorus unit.

Tony

http://takla-makan.bandcamp.com/
http://www.oakleysound.com