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 Forum index » DIY Hardware and Software » YuSynth
DIY minimoog filter bleeding through with no filtering
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chimneyanimals



Joined: Mar 06, 2015
Posts: 1
Location: uk

PostPosted: Fri Mar 06, 2015 9:22 am    Post subject: DIY minimoog filter bleeding through with no filtering Reply with quote  Mark this post and the followings unread

Hi, I'm pretty much a beginner building circuits so can anyone advise me on what might be going wrong? I built a minimoog vcf board a few years ago by sourcing parts myself. The filter seemed to work well, to my ears, and I recently built a casing for it, as well as a few other modules. Having recently wired up the filter again to the same power supply (which has always given the correct voltage readings) I immediately had a problem with the signal bleeding through, although sweeping the cutoff filtering was still evident (resonance responding etc). This was much worse without the env gen input in the control part of the circuit. With the env gen input there also seemed to be some strange inversion of the envelope going on, so I decided to change the transistors Q26 and Q28 in the control part of the circuit. I now just get bleed through without any filtering happening. It also seems that no current is actually going through the ladder, whereas before the current was proportional to the cutoff frequency. When i disconnect the resonance pot the bleed through also becomes louder. Any ideas?
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yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Thu Mar 12, 2015 12:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Check that the ground lugs of the jacks are connected to 0V rail. It sounds like there is no common ground between your modules.
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