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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
MFOS Dual Log/Lin VCA - value changes for +/- 15 V?
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Bodo1967



Joined: Aug 10, 2016
Posts: 15
Location: Germany

PostPosted: Wed Aug 19, 2020 3:21 am    Post subject: MFOS Dual Log/Lin VCA - value changes for +/- 15 V? Reply with quote  Mark this post and the followings unread

Hi everyone,

I'd like to add a few more VCAs to my system (completely DIY including cases and PSUs), which is kind of hybrid and has both +/- 12 and 15 V PSUs.

I'll add another 5U case in which I'd like to integrate one of the MFOS VCA modules. However, I't prefer to install only one PSU there, and that'll have to be a +/- 15 V one.

In the description, Ray writes somewhat vaguely:
"If you are using +/-15 volt supplies you will probably need to mess with some values to get this to work for you."

Did anyone here ever build a 15 V version, and if so, which values actually need to be replaced with which other values?

I'd like to spare myself the trial & error part, to be honest Laughing .
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jeephour



Joined: Dec 23, 2014
Posts: 3
Location: Sheffield

PostPosted: Thu Sep 03, 2020 6:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi

I think I got a 15v version.
Still need an answer?
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Bodo1967



Joined: Aug 10, 2016
Posts: 15
Location: Germany

PostPosted: Fri Sep 04, 2020 12:18 am    Post subject: Reply with quote  Mark this post and the followings unread

jeephour wrote:
Still need an answer?


Well yes... did you (have to) change any values and if yes, what are they?
Or does yours work nicely on 15V with all the original values in Ray's schematic?

Always provided your module works as it should, of course Wink.
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johans121



Joined: Jun 19, 2007
Posts: 178
Location: Huntsville, AL (USA)

PostPosted: Thu Dec 24, 2020 10:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Just out of curiosity, did you ever make any changes to your VCA for +/- 15V operation? I just got through putting one together. It works as it should. The problem is that it seems that the gain is relatively low as compared to my other 15V VCAs.

If I have the gain offset set to where I can not hear any audio when no CV is applied and then apply 10VPP input signal (say from a MOTM LFO) the output is indeed amplified but not to where I want it to be. In order to get the levels I want the gain offset needs to be boosted quite a bit but then there is a lot of input bleed through in the output.

Any help is appreciated.

_________________
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Bodo1967



Joined: Aug 10, 2016
Posts: 15
Location: Germany

PostPosted: Wed Nov 24, 2021 3:40 am    Post subject: Reply with quote  Mark this post and the followings unread

johans121 wrote:
Just out of curiosity, did you ever make any changes to your VCA for +/- 15V operation?


*cough* I only saw your post almost a year later...

Anyway - No, I didn't change anything and the VCA still works as expected Very Happy.
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