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 Forum index » DIY Hardware and Software » Musical Interfaces
Expand cv outputs.
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hway23



Joined: Jul 23, 2008
Posts: 61
Location: ks

PostPosted: Tue Aug 04, 2009 5:14 pm    Post subject: Expand cv outputs. Reply with quote  Mark this post and the followings unread

to control more oscillators and such, do I just add more jacks to the output of a midi cv, or do I need some sort of opamp to keep the voltage from dropping? Embarassed
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skylab76



Joined: Dec 30, 2007
Posts: 38
Location: Austin

PostPosted: Thu Aug 27, 2009 8:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey hway,

If I'm splitting from 1 in to 2 outs, I just a add a jack or a Y cable.

If I'm splitting from 1 in to 3 or more outs, I use an opamp . From my experiences, the voltage drops after 2. I just put together this simple CV distributor (1 in to 4 outs) found here:

http://www.musicfromouterspace.com/analogsynth/cvdistributor.html

regards,
JG
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Sebo



Joined: Apr 27, 2007
Posts: 564
Location: Argentina

PostPosted: Fri Aug 28, 2009 4:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi:
For pitch CV distribution I built this one:
http://www.musicfromouterspace.com/analogsynth/ControlVoltageDist/ControlVoltageDist.html
(The circuit at the right, but without the 100 ohms resistors). They are
simple voltage followers.
I recommend you to use some low drift, low offset opamps, I tried TL072
first, but they gave me an error up to 1 semitone, I used LF412 and worked
great.
I reported that here:
http://www.electro-music.com/forum/topic-33538.html

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https://www.facebook.com/cosaquitos/
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Antimon



Joined: Jan 18, 2005
Posts: 4145
Location: Sweden
Audio files: 371
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PostPosted: Sat Aug 29, 2009 11:53 am    Post subject: Reply with quote  Mark this post and the followings unread

In my Curetronic system, the multiple module is (by design) basically just 5 or 10 jacks connected in parallell - no power supply or ICs. Does this work differently for other systems, or should I expect (and possibly adjust for) a power drop if I hook to many things to the multiple?

/Stefan

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hway23



Joined: Jul 23, 2008
Posts: 61
Location: ks

PostPosted: Sat Aug 29, 2009 3:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
Hi:
For pitch CV distribution I built this one:
http://www.musicfromouterspace.com/analogsynth/ControlVoltageDist/ControlVoltageDist.html
(The circuit at the right, but without the 100 ohms resistors). They are
simple voltage followers.
I recommend you to use some low drift, low offset opamps, I tried TL072
first, but they gave me an error up to 1 semitone, I used LF412 and worked
great.
I reported that here:
http://www.electro-music.com/forum/topic-33538.html


Yup, that's what I was looking for. Thanks!
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emdot_ambient



Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD

PostPosted: Mon Apr 19, 2010 1:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Antimon wrote:
In my Curetronic system, the multiple module is (by design) basically just 5 or 10 jacks connected in parallell - no power supply or ICs. Does this work differently for other systems, or should I expect (and possibly adjust for) a power drop if I hook to many things to the multiple?

Most multiple modules are passive circuts but, yes, you should expect a slight drop in Voltage when using them. As mentioned above, if you split too many CVs the voltage drop will cause issues (oscillator pitch tracking).

Found some good info on it here in the comments section.

For most uses it's not a problem. But for pitch related and precision CV work--like controlling frequency on multiple VCFs when one or more are in self oscillation and you want them to track pitch--it's best to use powered splitters like those linked.

Splitting audio signals with multiples isn't so much an issue. You'll lose some amplitude at worst. Probably not an issue with triggers and gates either.
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Antimon



Joined: Jan 18, 2005
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PostPosted: Mon Apr 19, 2010 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

emdot_ambient wrote:
Antimon wrote:
In my Curetronic system, the multiple module is (by design) basically just 5 or 10 jacks connected in parallell - no power supply or ICs. Does this work differently for other systems, or should I expect (and possibly adjust for) a power drop if I hook to many things to the multiple?

Most multiple modules are passive circuts but, yes, you should expect a slight drop in Voltage when using them. As mentioned above, if you split too many CVs the voltage drop will cause issues (oscillator pitch tracking).

Found some good info on it here in the comments section.

For most uses it's not a problem. But for pitch related and precision CV work--like controlling frequency on multiple VCFs when one or more are in self oscillation and you want them to track pitch--it's best to use powered splitters like those linked.

Splitting audio signals with multiples isn't so much an issue. You'll lose some amplitude at worst. Probably not an issue with triggers and gates either.


Late but great answer there - thanks! Smile It matches what I've experienced - I'm glad to get it confirmed. I've especially wondered about how the pitch sometimes drops a notch when I plug in something.

/Stefan

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emdot_ambient



Joined: Nov 22, 2009
Posts: 667
Location: Frederick, MD

PostPosted: Mon Apr 19, 2010 2:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
I built this one:
http://www.musicfromouterspace.com/analogsynth/ControlVoltageDist/ControlVoltageDist.html
(The circuit at the right, but without the 10k ohms potentiometers).

Fixed that for you Wink

You also added a cap between the + and - rail.
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Sebo



Joined: Apr 27, 2007
Posts: 564
Location: Argentina

PostPosted: Mon Apr 19, 2010 4:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

emdot_ambient wrote:
Sebo wrote:
I built this one:
http://www.musicfromouterspace.com/analogsynth/ControlVoltageDist/ControlVoltageDist.html
(The circuit at the right, but without the 10k ohms potentiometers).

Fixed that for you Wink

You also added a cap between the + and - rail.


My statement was right, the circuit at the right doesn't have pots, so I built
that circuit without the 100 ohms resistors.
And yes, I added 100nF decoupling caps to every chip and a two 22uF
electrolitics at power input (one for +15, one for -15).

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https://www.facebook.com/cosaquitos/
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