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ARP 2600 - CV control of Volume/VCA?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author ARP 2600 - CV control of Volume/VCA?
mr anxiety
Curious if anyone knows how to control the 2600 via midi>CV for volume-VCA?
I am able to control the Filter, but I can't find a patch point that allows control of the VCA anywhere.

There are 2 cv ins for the VCA - normalled to the AR and ADSR. One is linear, the other exponential. Pick one.
mr anxiety
I believe I tried those already and I didn't get any result from either. I will try them again.

mr anxiety
Well, you're correct in the AR control input can control the AR, but it doesn't control the ADSR, which I use a lot and needs control as well for a master volume type situation. So I am still in search of a situation. I might need to resort to a analog volume pedal at the very last output of the 2600. Less than ideal.

Thanks for your help!
You might be able to do this using the Ring Modulator. Run the output of your VCA to the left input of the Ring Modulator. Run your volume pedal into the right input of the Ring Modulator. Connect the Ring Modulator output to your monitors. Put the Ring Modulator in DC mode and then turn up both input sliders fully. Now your pedal should work. Good luck!
Ah, I see, you're looking for basically another VCA. Yes, as wes2600 says, you can use the RM as a VCA - I just tried it, it works well.
mr anxiety
Thanks Wes and SDuck for your suggestions.

Yes, I'm using an Expressionist (midi to cv/gate converter) to try and control elements of my hardware synths in my DAW, mainly Filter settings, some LFO, and Volume, which is what I'm after on my 2600.

The ring modulator suggestions sort of works introducing a CV control into the right side of the RM, but it doesn't completely control the output for some reason, only half of the volume and the tone becomes fizzy as well.

When using this CV control into the AR control jack on the VCA mixer section, the volume is controlled, but the output starts sustaining, like if the Initial Gain slider was engaged, which it is not! Using the ADSR control jack does not do anything. I'm a bit perplexed with this.

Again, thanks for your help!
Delta T
If I understand what you’re asking, you should be able to control the VCA using either the AR or ADSR inputs below the VCA. Select one and connect your CV to it and make sure the slider above it is up...start with it all the way up. For testing make sure the slider above the other input is down. I’ve used Silent Way many times with an ES-III to do just this.

Also make sure the VCA level control above the VCA diagram is all the way to the left (the further to the right it is the louder your minimum volume will be.)

Feed a signal into the VCA input and operate your CV some point you should hear sound following your CV input. Adjust the level of the CV going to the VCA using the slider above the input. You can connect another CV to the other input and use it for complex modulation.

Remember if you are trying to use the internal AR or ADSR with an external CV source like a sequencer you need to connect gate and trigger...
mr anxiety
Delta T, thx for chiming in. I am doing everything you've mentioned. Everything is working fine, my CV in to the VCA is controlling the volume of the 2600, except the sound produced is infinitely sustaining, even though the patch is not set up to sustain. So I'm getting this sustain from my CV in to the VCA somehow. Very strange. And yes, the initial gain slider is all the way to the left, so that is not the cause of it. Gate/Trigger is patched and working successfully.
It's just this sustain issue now.
Are you 100% sure your cv source is going to zero?
Here's my guess - I suspect that you are feeding an envelope into one CV input of the VCA, to form the note shape, and a constant CV into the other, expecting that to control the overall volume of the note. That's not how the VCA works (I think, not having a 2600 handy) - both CVs are added together, so both of them need to be zero to silence the output. Instead, you are adding a constant offset to the envelope.
Delta T
Another the right of the VCA controls is the mixer section. Make sure the VCF slider is down. That allows audio from the VCF to bypass the VCA and any effect it would have on volume. Obviously the VCA slider (in the mixer section) needs to be up...
mr anxiety
From my view here, everything looks set up right with my converter sending cv control to control volume at the AR control in at the VCA mixer.

Delta T, the VCF slider is always down, but good idea to check.

I'm losing energy to sort this out. All I'm hoping to do is to make 2600 volume adjustments in my DAW as I work.

Thanks everyone for helping try to sort this out.

Mr A
mr anxiety wrote:
From my view here, everything looks set up right with my converter sending cv control to control volume at the AR control in at the VCA mixer.

Tell us about the CV you are sending to control the volume. Is it a constant voltage (as long as you are playing at a constant volume)? Or does it start at 0V, rise when the note sounds, and return to 0V when the note ends?
Never used MIDI. Is the Initial Gain set far left to 0? Does that matter? Apologies if that is overly obvious and irrelevant.
mr anxiety
Yes, it would matter, but Initial Gain is all the way to left, so no sustain from that.

Delta T
Another quick thought...the midi signal you are sending to your it going down to 0 or is it hovering around its mid-point? Depending on the midi signal, some will stay at 64 and cycle above and below. If possible, take a voltage measurement at the tip of your cv cable. It should be 0 when you send it your midi volume of zero. Some cv signals/converters will hold the last voltage sent to them...they don’t drop back to zero after the note or command is done. Also, what are you driving your converter with?

Is it possible to get pic of the 2600 panel with your cabling in place?
mr anxiety

Here's what I have going on with the 2600.
1. Oh, I am sending midi pitch and gate/trigger info from my Yamaha P300 piano controller via Cubase 9. Using an Expressionist as my midi to CV convertor. Am successful in sending to a variety of other synths with this set-up... Roland MC-202, Roland SH-3, Oberheim FVS.

A. I am sending CV to the far left kyb CV control via the mult below it. I am also using the mult to apply lag processor to VCO 3.
B. The Gate and Trigger are being sent to the AR section inputs
C. I'm sending a 2nd CV to the VCF via the kyb CV control input. This is working smoothly BTW.
D. My problematic patch is the 3rd CV I'm sending to the AR control input in the VCA section. Using a similar setup to the VCF cv patch, but this adds a sustain to the sound as it sweeps the amplitude/volume. FYI - The Initial Gain is at minimum.
mr anxiety wrote:

D. My problematic patch is the 3rd CV I'm sending to the AR control input in the VCA section. Using a similar setup to the VCF cv patch, but this adds a sustain to the sound as it sweeps the amplitude/volume.

If this CV is greater than zero, then it will turn on the VCA. I suspect that's your problem.
mr anxiety
I want to thank everyone for contributing to my solution to controlling the 2600 volume via midi, using an Expressionist as a midi to cv controller and Cubase/midi controller as my midi source.

The only solution I found was one suggested in this thread by a couple of people - using the Ring Modulator. I was finally able to get this to work, taking the VCA output and putting in the Right side of the RM, and putting my ext CV control to the Left side. The output of the RM went to the VCA input in the Mixer. This patch allowed the volume to be controlled to 60% of it's range, so it never went to 0 volume, as well as the polarity was reversed, so the volume went lower as the slider on the ext CV went higher.

So we solved this issue by putting the ext CV into input 5 of the third Voltage Processor - +10 v and the output from that inverter to the Left side of the RM.
By moving the slider of this inverter, I was able to find "0" volume at the bottom of the slider range and therefore solved my problem.

I hope this helps the next person searching for a solution like this.

Best, Mr Anxiety
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