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SOLVED - Serge Log/Lin VCA Woes...
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AndyR1960



Joined: Feb 16, 2007
Posts: 281
Location: Manchester UK
Audio files: 5

PostPosted: Sun Jul 01, 2012 12:05 pm    Post subject: SOLVED - Serge Log/Lin VCA Woes... Reply with quote  Mark this post and the followings unread

OK, so I'm on the last leg of trouble shooting my synth...

I built Marjan Urekar's Serge Log/Lin VCA (http://members.tripod.com/urekarm/synth/serge_vca.pdf)

The problem is, I'm not getting any response to any CV at the linear IP. The Log section works great though.

Has anybody built this VCA, did you have any problems etc?

What I'm after is a Log/Lin VCA that can utilise both CV inputs at the same time (most VCA's like this involve switching between Log & Lin, which I would like to avoid).

I built the ARP 2600's amp, which works well, except I'm getting serious thump from the envelopes, and the CV reject trimmer does nothing to help Rolling Eyes

Any pointers would be much appreciated.

Cheers.

EDIT - Finally solved the problem with the ARP VCA... Pulled the three transistor pairs and matched them (not matched previously). Works great, better than the standard OTA VCA's, seems to have much more punch Very Happy
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noiselector



Joined: Mar 30, 2013
Posts: 21
Location: France

PostPosted: Sun Jun 02, 2013 4:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

I would like to built the arp 2600 vca section, could you share some layouts ?
Did you use 2N3904/2n3906 for matched transistor pairs?

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noiselector



Joined: Mar 30, 2013
Posts: 21
Location: France

PostPosted: Sun Jun 02, 2013 4:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

2N3906 as an alternative for 2N6076 and 2n3904 for 2n5459 too?
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