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Audio Signal (Constant)
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Audio Signal (Constant)
Steverido
Is it normal to have a constant audio signal coming from the Eurorack through a DC coupled soundcard and into a DAW? I have tried various patching and it increases or decreases depending on the signal path.

For example, if I patch from my VCO to the VCA and then to the soundcard and into the DAW, I get less signal. Signal is from 230Hz to 22Khz

Naturally I would expect audio signal if patched through a reverb device.

Is this normal?

See image
Nagasaki45
Yeah, there's a bit of noise coming from any audio gear. Last time I checked my setup was really noisy, around -45db. But I'm using it mainly for live performance so for me it's OK. Does it bother you? Is it too loud for what you need / expect from your equipment? There are ways to improve these things (which usually involve spending more money). I'm sure other people will be able to troubleshoot / help you better than I do.
cornutt
Not sure what you're asking, but it sounds like your VCA may not be closing down all the way. It's normal for a VCO to produce a signal all the time when it is powered -- that's the way most of them work. If your VCA has an "initial gain" control, check to see that it is turned all the way down.
Pelsea
-70 dB is a good enough number, and represents "off" for most VCAs. If it is a problem, use two VCAs in series. With some models, linear mode is quieter than log.
wackelpeter
As others have said, most likely the VCA isn't closed fully or if you use a mixer module than it could be a missing Ground on the pot to attentuate the Signal... normally one lug gnd, middle goes to summing node and the other lug opposite to the gnd is the Signal Input... when there the gnd is not really connected you will have the Signal greatly reduced but not totally muted and still enough to feed through…
Steverido
Thanks for all of the responses.

Looks like it is nothing to concrn myself with. applause
Synthbuilder
I think it's a zero volt or 0V (often called local ground) problem. The modules in your case all share the same 0V line. It's both the reference for the audio signals, CV signals and the power supply. Any electrical resistance in the 0V connections will cause the 0V to not become 0V anymore and it will be different across your modular system. Those differences will create unwanted audio signals on all outputs which is called crosstalk. Crosstalk can never be minimised completely but it shouldn't be noticeable. However, what is tolerated by one user may not be acceptable to another. Personally I wouldn't want that level of crosstalk if that is what it is.

Power distribution strips should be short and well designed. They should be fed from the power supply with the thickest and shortest wires you can fit. Likewise the power cables to the modules should be as short as possible and only be used to power one module. Daisy chaining modules with long lengths of ribbon cable is a recipe for crosstalk and should be avoided.

Busbars are the best way forward though but they do require a decent sized case to put them in.

Tony
Steverido
Synthbuilder wrote:
I think it's a zero volt or 0V (often called local ground) problem. The modules in your case all share the same 0V line. It's both the reference for the audio signals, CV signals and the power supply. Any electrical resistance in the 0V connections will cause the 0V to not become 0V anymore and it will be different across your modular system. Those differences will create unwanted audio signals on all outputs which is called crosstalk. Crosstalk can never be minimised but it shouldn't be noticeable. However, what is tolerated by one user may not be acceptable to another. Personally I wouldn't want that level of crosstalk if that is what it is.

Power distribution strips should be short and well designed. They should be fed from the power supply with the thickest and shortest wires you can fit. Likewise the power cables to the modules should be as short as possible and only be used to power one module. Daisy chaining modules with long lengths of ribbon cable is a recipe for crosstalk and should be avoided.

Busbars are the best way forward though but they do require a decent sized case to put them in.

Tony


Thanks Tony. Perhaps it is crosstalk. I have a TipTop Audio uZeus which is daisy chained. The only option would be to change my skiffs. I currently use the small and a large Moog Mother cases.

Do you think something like Hinton in the link below?

http://hinton-instruments.co.uk/paprod/psu/distribution.htm
Synthbuilder
Steverido wrote:
I have a TipTop Audio uZeus which is daisy chained.

That may indeed be the cause of the problem. It does depend a little of what modules you have but a daisy chained system is never the best choice.

Quote:
Do you think something like Hinton in the link below?

http://hinton-instruments.co.uk/paprod/psu/distribution.htm

Graham makes fantastic power systems. They are at the premium end of the power distribution spectrum with daisy chained ribbon cables at the other. In small setups it may not be necessary to go the busbar route as a standard Doepfer one, or similar, may suffice. The bigger the current draw of your modules the more you have to think about how power is distributed. If you want the best then a Hinton busbar system with improved power connectors is the way to go.

Tony
Dave Peck
You haven't explained what this leaking audio signal sounds like. Is it just white noise? Or can you actually hear the oscillator?

It could just be residual noise generated by the VCA or whatever module is at the end of the chain if it sounds like white noise. Check your gain staging to make sure your signal levels are at the best setting to minimize noise and still avoid clipping.

Or it could be crosstalk or bleed if you can actually hear sound sources that are in the patch, like the output of an audio oscillator. This could be a leaky VCA that isn't closing all the way, or it could be due to shortcomings in the power distribution.
Steverido
Hey Guys,

Thanks for all of your help, much appreciated.

I have found out what the problem is. It is my Motu Ultralite MK3 input 1 channel. The AD converters are damaged.
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