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 Forum index » DIY Hardware and Software » Developers' Corner
Simple VCA for drum module
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mrkva



Joined: Jan 25, 2012
Posts: 41
Location: poland/slovakia/netherlands

PostPosted: Fri Mar 09, 2012 4:00 pm    Post subject: Simple VCA for drum module Reply with quote  Mark this post and the followings unread

Hello fellow developers.

I am designing simple drum module (white noise -> decay + vca + low pass filter) and I was wondering if there is an easy VCA solution for that. It seems to be a little too expensive and wasteful to use CA3080 for this.
Do you have some ideas maybe? Thanks

Mrkva
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richardc64



Joined: Jun 01, 2006
Posts: 614
Location: NYC
Audio files: 25

PostPosted: Sat Mar 10, 2012 6:46 am    Post subject: Reply with quote  Mark this post and the followings unread

I've had some success with a simple transistor plus op amp arrangement, as shown in the examples below, and my experimental circuit.

The signal is input at the transistor collector, output at the emitter, with CV applied to the base.The input should be limited to 1volt or so, then amplified up to the level desired. More signals that will have the same envelope shape can be mixed in at the collector. More signals having different enveloping can be added by tying more transistors' emitters together, as in the '909 or '505. The op amp can be split supply as in the '909, or single-supply, as in the '505 or not shown in my experimental circuit.

Also, look here:
http://electro-music.com/forum/viewtopic.php?highlight=transistor+vca&t=33190 (Search is your friend -- sometimes.)


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mrkva



Joined: Jan 25, 2012
Posts: 41
Location: poland/slovakia/netherlands

PostPosted: Sat Mar 10, 2012 7:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks! I was trying to design something similar from scratch, but this looks better!
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