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 Forum index » DIY Hardware and Software » Thomas Henry designs
VCA-1: Eliminating the "initial" pot.
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reve



Joined: Feb 23, 2008
Posts: 149
Location: USA

PostPosted: Wed Feb 09, 2011 11:01 pm    Post subject: VCA-1: Eliminating the "initial" pot. Reply with quote  Mark this post and the followings unread

Hi Everyone!

So I wound up with a CEM3360 Dual VCA chip. Drilled a panel, laid the circuit out on a breadboard only to found out the chip was bad. (This may or may not have been me frying the chip. I can still use the bad chip excuse, though -- it's bad now!) So I figured hey, nice opportunity to build a couple VCA-1s, right?

Thing is, I hate to chuck the panel I already drilled... which does not account for "initial" level pots. BUT this was to be a dedicated final VCA. It will never see anything but a 0-10v envelope as a CV source.

So if that's the case, do I need the initial pot? Couldn't I just replace it with a trimmer... or eliminate it all together?

Thanks guys...

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SynthDIY Synthpop -> http://www.reverbnation.com/photovoltaik
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Clack



Joined: Aug 08, 2005
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PostPosted: Thu Feb 10, 2011 1:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Trimmer would be best as you have to set it at the right point.

It just means you will have less options , and say if your cv is a little bit offset you can't quickly correct it.

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reve



Joined: Feb 23, 2008
Posts: 149
Location: USA

PostPosted: Sun Feb 13, 2011 1:42 am    Post subject: Re: VCA-1: Eliminating the "initial" pot. Reply with quote  Mark this post and the followings unread

reve wrote:

So if that's the case, do I need the initial pot? Couldn't I just replace it with a trimmer... or eliminate it all together?


Well, I decided to forego the breadboard process and build a dualie on protoboard. I left the initial pot (and R23) off, and I also left out the offset trimmer (and R15).

Aaaaannnd I'm happy (and kinda surprised) to say it works great. I forgot to use beads and the noise floor is negligible.

So if you don't care about bipolar control signals... leavin' 'em off worked for me.

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