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Advice on external CV into a VCS3
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge  
Author Advice on external CV into a VCS3
chamomileshark
hi, I wondered if there was any advice on this - in particular if there is anything you shouldn't do that might cause damage.

I'm thinking about sending audio signals from a Revox into the CV (not audio in) - would that be safe if I keep levels down and turn up gradually?

Then for more classic CV sources, e.g wogglebug or other modules - any thing to be aware of?

thanks
papz
As long as you don't connect 220V AC to your VCS3's input, the worst thing which could happen is you overdrive the input amps.

The input channels are the same ones for CV or audio.
The mic 600 ohms inputs are for mic or guitars etc...
The hi level inputs are for line level signals and CV (patch CV via a 100k resistor otherwise high CV will overdrive the input amp and have no action).

Do not use both inputs of the same channel at the same time, but you can use for example the mic input of ch1 and the hi level input of ch2.

Anyway keep levels down and turn up gradually is a good idea, but keep in mind that the input level pots are at the output of the input amps, they won't help attenuate the signal sent to the input amp but the one at it's output, available on rows 8 or 9.
ersatzplanet
Keep in mind also that the CV response of the Synthi VCOs is quite different than that of any synths on the market today that you would be connecting with. The Synthi stuff was at 0.32V/octave and not 1V/octave as most things are today. The input levels will most likely have to be scaled down quite a bit to track perfectly.

As for audio - the two high level inputs on the VCS3 and the AKS can take audio or DC and work fine. I used to modify stuff all the time though mine with no problems. Remember that signals sent to the VU meter will also show up on the scope output but inverted. very useful sometimes.
papz
The signals sent to the scope are not inverted.
The scope out is connected directly to the matrix column, no inverter on the way.

Maybe what misleads you is the common inverting patch : a signal sent to the scope output and patched with a jack cable into an input is available inverted on the corresponding matrix row.
Indeed.
The input amps are inverters actually, and the tracking of the oscillators 1 and 2 is not about 0.32V/oct but well about -0.32V/oct (osc 3's is about -0.26V/oct).
chamomileshark
hi, thanks for the answers and advice, that's really helpful.
chaircrusher
I don't know how much voltage it would take to damage a Putney input. Just last night I hooked up the VCS3 to the CV/Gate output of a Keith McMillan QuNexus and it worked fine, or as fine as a VC3 can. The QuNexus CV outs are limited to 0-5V because it uses the USB power rail.

I also ran it from Roland MPU101 with the 10K resistors. EDIT 100K resistor!

I never got it to track more than 2 octaves, and as soon as you plug in other pins -- i.e. to mod frequency with another oscillator, it goes wonky.

I've tried to control 2 oscillator's pitch from one CV input and getting them tuned and scaled properly isn't really going to happen.

chamomileshark wrote:
hi, I wondered if there was any advice on this - in particular if there is anything you shouldn't do that might cause damage.

I'm thinking about sending audio signals from a Revox into the CV (not audio in) - would that be safe if I keep levels down and turn up gradually?

Then for more classic CV sources, e.g wogglebug or other modules - any thing to be aware of?

thanks
papz
Resistors are supposed to be 100k, not 10k.

Other pins plugged changing the osc frequency is normal behaviour on an unbuffered device.

A good working properly calibrated VCS3 tracks on 5 octave and sometimes more (but the accurate adjustment of the input level pots is tricky). If yours doesn't, he probably needs servicing.
chaircrusher
The thing is old enough to have grandchildren; I'm sure it needs servicing ;-)

papz wrote:
Resistors are supposed to be 100k, not 10k.

Other pins plugged changing the osc frequency is normal behaviour on an unbuffered device.

A good working properly calibrated VCS3 tracks on 5 octave and sometimes more (but the accurate adjustment of the input level pots is tricky). If yours doesn't, he probably needs servicing.
Scot Solida
papz wrote:

A good working properly calibrated VCS3 tracks on 5 octave and sometimes more (but the accurate adjustment of the input level pots is tricky).


Indeed. Mine is by no means perfectly calibrated, but tracks very well once I have the input levels properly set.
papz
Some replace the input level pots with a multiturn type to ease accurate adjustment.
aonghus
A question regarding CV input.

I've read upthread that you are supposed to wire a 100k resistor into your CV cable before plugging it into the VCS3. So when you cut open a patch cable and there are two strands of wire (one that's wrapped and another strand outside it), which strand do you wire the resistor onto?

Thanks
papz
Onto the "wrapped" one, it is the signal.
The "wrapping" one is ground.
B-ry
Thanks for all the pointers.

VCS3 is a different type of animal. It’s good to RTFM as well as pick up advice from a few veterans.

Cheers!
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