Synth-DIY Yahoo! Groups Archives

Thread

silly question

2000-04-18 by Nathan Alan Hunsicker

Is there any simple circuit that could be made to permit voltage control
over any pot? My question probably doesn't make much sense, and with my
limited electrical knowledge, I probably won't explain it very well
either. What I was thinking of was  a circuit designed to simulate a
pot. A simple circuit with a CV in, a CV attenuator, and 3 wires to
replace the pot, 2 to provide a constant resistance and one to vary
according to CV. This would be a simple solution to those of us who want
voltage control over the freq. on their MOTM-420's or the wet/dry
control on a spring reverb. Maybe I'm out of my mind here, and this is
an impossibility, but it's worth throwing out. Let me know if it's
possible or if it would involve too much circuitry. -Nate

RE: [motm] silly question

2000-04-18 by Dave Bradley

It takes 1 of 2 approaches to replace a pot with a cv, based on the
situation.

1. replacing a pot that just provides a control voltage in the first place -
no problem, you just tap into the summing amp with an input.

2. replacing an arbitrary pot that carries signal, for example the resonance
pot on a filter - you have to replace the pot with a simple VCA, so it's
nontrivial.

Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...

Show quoted textHide quoted text

> -----Original Message-----
> From: David Bivins [mailto:dbivins@...]
> Sent: Tuesday, April 18, 2000 12:36 PM
> To: motm@egroups.com
> Subject: RE: [motm] silly question
>
>
> I see your point, but--
>
> Don't you already have voltage control over frequency on your 420s?! You
> should have three inputs that will control the cutoff frequency
> via voltage,
> labeled: 1V/OCT, FM1, and FM2. What you *don't* have is voltage
> control over
> resonance amount. You do get that (as well as cutoff control) on the 440.
>
> I don't know the technical answer to your question, but having
> asked similar
> questions on AH awhile back and getting learned responses from
> the likes of
> Kevin Lightner and probably Paul too, the answer is no. With some circuits
> it might be a simple matter, with others, not a simple matter. So there
> would be no "generic" approach that would work.
>
> David.
>
> > -----Original Message-----
> > From: Nathan Alan Hunsicker [mailto:nate@...]
> > Sent: Monday, April 17, 2000 8:29 PM
> > To: MOTM Newsgroup
> > Subject: [motm] silly question
> >
> >
> > Is there any simple circuit that could be made to permit voltage control
> > over any pot? My question probably doesn't make much sense, and with my
> > limited electrical knowledge, I probably won't explain it very well
> > either. What I was thinking of was  a circuit designed to simulate a
> > pot. A simple circuit with a CV in, a CV attenuator, and 3 wires to
> > replace the pot, 2 to provide a constant resistance and one to vary
> > according to CV. This would be a simple solution to those of us who want
> > voltage control over the freq. on their MOTM-420's or the wet/dry
> > control on a spring reverb. Maybe I'm out of my mind here, and this is
> > an impossibility, but it's worth throwing out. Let me know if it's
> > possible or if it would involve too much circuitry. -Nate
> >
> > ------------------------------------------------------------------------
> > Calling all Jazz fans. Check out DownBeatJazz.com's Digital Downloads
> > section where you can download free mp3s. If you're a musician, upload
> > your songs to DownBeatJazz.com for a chance to get reviewed by Down
> > Beat Editors!
> > http://click.egroups.com/1/2142/3/_/529958/_/956024824/
> > ------------------------------------------------------------------------
> >
> >
>
>
> ------------------------------------------------------------------------
> Your high school sweetheart-where is he now?  With 4.4 million alumni
> already registered at Classmates.com, there's a good chance you'll
> find her here. Visit your online high school class reunion at:
> http://click.egroups.com/1/3139/3/_/529958/_/956071955/
> ------------------------------------------------------------------------
>
>

RE: [motm] silly question

2000-04-18 by David Bivins

I see your point, but--

Don't you already have voltage control over frequency on your 420s?! You
should have three inputs that will control the cutoff frequency via voltage,
labeled: 1V/OCT, FM1, and FM2. What you *don't* have is voltage control over
resonance amount. You do get that (as well as cutoff control) on the 440.

I don't know the technical answer to your question, but having asked similar
questions on AH awhile back and getting learned responses from the likes of
Kevin Lightner and probably Paul too, the answer is no. With some circuits
it might be a simple matter, with others, not a simple matter. So there
would be no "generic" approach that would work.

David.

Show quoted textHide quoted text

> -----Original Message-----
> From: Nathan Alan Hunsicker [mailto:nate@...]
> Sent: Monday, April 17, 2000 8:29 PM
> To: MOTM Newsgroup
> Subject: [motm] silly question
>
>
> Is there any simple circuit that could be made to permit voltage control
> over any pot? My question probably doesn't make much sense, and with my
> limited electrical knowledge, I probably won't explain it very well
> either. What I was thinking of was  a circuit designed to simulate a
> pot. A simple circuit with a CV in, a CV attenuator, and 3 wires to
> replace the pot, 2 to provide a constant resistance and one to vary
> according to CV. This would be a simple solution to those of us who want
> voltage control over the freq. on their MOTM-420's or the wet/dry
> control on a spring reverb. Maybe I'm out of my mind here, and this is
> an impossibility, but it's worth throwing out. Let me know if it's
> possible or if it would involve too much circuitry. -Nate
>
> ------------------------------------------------------------------------
> Calling all Jazz fans. Check out DownBeatJazz.com's Digital Downloads
> section where you can download free mp3s. If you're a musician, upload
> your songs to DownBeatJazz.com for a chance to get reviewed by Down
> Beat Editors!
> http://click.egroups.com/1/2142/3/_/529958/_/956024824/
> ------------------------------------------------------------------------
>
>

RE: [motm] silly question

2000-04-18 by Nathan Hunsicker

Sorry for the mistake, I meant resonance. I was more looking to have
voltage control over the reverb and vibrato controls on my amp. I thought
there would be an easy way to create  a voltage controlled variable
resistor. -Nate

Show quoted textHide quoted text

>
>I see your point, but--
>
>
>
>Don't you already have voltage control over frequency on your 420s?! You
>
>should have three inputs that will control the cutoff frequency via voltage,
>
>labeled: 1V/OCT, FM1, and FM2. What you *don't* have is voltage control over
>
>resonance amount. You do get that (as well as cutoff control) on the 440.
>
>
>
>I don't know the technical answer to your question, but having asked similar
>
>questions on AH awhile back and getting learned responses from the likes of
>
>Kevin Lightner and probably Paul too, the answer is no. With some circuits
>
>it might be a simple matter, with others, not a simple matter. So there
>
>would be no "generic" approach that would work.
>
>
>
>David.
>
>
>
>> -----Original Message-----
>
>> From: Nathan Alan Hunsicker [mailto:nate@...]
>
>> Sent: Monday, April 17, 2000 8:29 PM
>
>> To: MOTM Newsgroup
>
>> Subject: [motm] silly question
>
>>
>
>>
>
>> Is there any simple circuit that could be made to permit voltage control
>
>> over any pot? My question probably doesn't make much sense, and with my
>
>> limited electrical knowledge, I probably won't explain it very well
>
>> either. What I was thinking of was  a circuit designed to simulate a
>
>> pot. A simple circuit with a CV in, a CV attenuator, and 3 wires to
>
>> replace the pot, 2 to provide a constant resistance and one to vary
>
>> according to CV. This would be a simple solution to those of us who want
>
>> voltage control over the freq. on their MOTM-420's or the wet/dry
>
>> control on a spring reverb. Maybe I'm out of my mind here, and this is
>
>> an impossibility, but it's worth throwing out. Let me know if it's
>
>> possible or if it would involve too much circuitry. -Nate
>
>>
>
>> ------------------------------------------------------------------------
>
>> Calling all Jazz fans. Check out DownBeatJazz.com's Digital Downloads
>
>> section where you can download free mp3s. If you're a musician, upload
>
>> your songs to DownBeatJazz.com for a chance to get reviewed by Down
>
>> Beat Editors!
>
>>
>><http://click.egroups.com/1/2142/3/_/529958/_/956024824/>http://click.egroups.co
>>m/1/2142/3/_/529958/_/956024824/
>
>> ------------------------------------------------------------------------
>
>>
>
>>
>
>
>
>
>
>

RE: [motm] silly question

2000-04-18 by Doug Pearson

Resonance CV can be added to a filter by using an external VCA:

1) Run the output of your -420 into a multiple.

2) One of the multiples is your "main" out.

3) Run the other multiple through a VCA, then back into the second audio
input of the -420.

4) The CV of the VCA will then be resonance CV (and the input attenuator of
the second audio input will also control resonance amount).

The same method could also be used to get voltage-controlled feedback for
an analog or digital delay.

For the amplifier, you'd have to tap into the "wet" reverb and vibrato
lines, and bring them each through a VCA.  There would be plenty of room
inside most amps, I would think, to stick two VCA's and (if necessary) the
regulators to run them.  Not a trivial mod, however. (I assume that you're
talking about vibrato AMOUNT, as this wouldn't work for vibrato SPEED.)

At 01:52 PM 04/18/2000 -0400, Nathan Hunsicker <nate@...> wrote:
>Sorry for the mistake, I meant resonance. I was more looking to have
>voltage control over the reverb and vibrato controls on my amp. I thought
>there would be an easy way to create  a voltage controlled variable
>resistor. 

A VCA with a maximum gain of unity would behave as a voltage-controlled
variable resistor for the signal flowing through the VCA.

Somebody correct me if I'm wrong!

	-Doug
	 ceres@...

Re: [motm] silly question

2000-04-19 by davevosh@aol.com

In a message dated 00-04-18 08:59:01 EDT, you write:

<< I wonder if there isn't some generic circuit that could do this >>



ken,
wouldn`t this be an ota circuit ( 3080,3280,13xxx  type ) ?
best,
dave v.