Muff's Modules & More

thomachine · Posted: Tue Mar 06, 2012 12:19 pm Post subject: Bleedthrough Intellijel modules.

I have Both Corgasmatron, and a uVCA. And i am experiencing some bleedthrough on both modules. Nothing real bad, but enough to bother me.

On the Corgasmatron if i run both as sine oscs, i can hear filter one out of the filter two output, and vice versa. Same with the mix output. I will hear some of the other osc, even if i turn the xfade in the opposite direction.

And on the uVCA, i will hear whats going in to the vca B, even with all knobs turned down, and nothing but the input cable connected.

So since im new to the modular world, is there a way to adjust these modules?

Mitchk1989 · Posted: Tue Mar 06, 2012 12:27 pm Post subject:

sounds like a PSU issue to me if it's enough bleedthrough to bother you. I can get some with those modules doing what you describe, but not enough to be at all audible without cranking the gain on my system high enough to deafen with regular level sounds.

dualmono · Posted: Tue Mar 06, 2012 12:37 pm Post subject:

I will check it out once I'm home and report.

thomachine · Posted: Tue Mar 06, 2012 12:56 pm Post subject:

As i said, its not that much of a problem. In a patch, i often use one sine from the corgasmatron through uVCA B, to modulate waveshape or fm on my osc. And uVCA A is the overall volume controller. And its connected to my soundcard. So when recording, and no gate/env is sent to the uVCA A, i hear a high pitched note from the corgasmatron. And some extra editing is needed in my DAW. So the vca bleed is more of a problem than the corgasmatron...

a scanner darkly · Posted: Tue Mar 06, 2012 1:14 pm Post subject:

Re: Corgasmatron - try adjusting the trim pot marked XFade Adj.

msprigings · Posted: Tue Mar 06, 2012 1:27 pm Post subject:

My Korgasmatron has bleed I need to check that trim.

haven · Posted: Tue Mar 06, 2012 2:17 pm Post subject:

It is helpful to contact the manufacturer first with technical problems like this. intellijel support can be reached at support@intellijel.com

I have not noticed significant bleed between channels, some things to check.

Power supply as mentioned, also is the BIAS on VCA A all the way down? Do you have proper gain staging set so that a full signal coming out of the VCA does not distort your audio interface? CV knob on the VCA should be fully clock wise and a 5V envelope coming in. Sometimes people have too much gain on their modular output signal. Then the low level bleed and noise in the system will be amplified too high. You should need no gain, just attenuation (negative gain).

The MIX out of the Corgasmatron can bleed, the trimmer on the xfade board will trim it out. Set Xfader fully CCW, parallel mode. make A resonate and then adjust the trimmer slowly until you cannot hear A.

I use a scope to calibrate them make A and B resonate, A higher pitch than B. hook the mix out to the scope and adjust until A is no longer present as modulation over B.

mojopin · Posted: Tue Mar 06, 2012 3:37 pm Post subject:

I only have the uVCA. Yes, there is bleed but for all practical purposes it shouldn't be an issue. I have a high quality linear psu from Hinton Instruments so I don't think that is the issue. As mentioned, make sure your bias is all the way down. If your signal is past 10k then you can hear it barely but a normal signal coming out of the modular would mean that I wouldn't have it that loud for it to be a problem. One solution would be to get another vca for modulation duties. Another thing to remember is that the 'noise floor' of patches can sometimes have stray modulations noises. It doesn't really bother me but sometimes it does need to be dealt with. The other day I used an expander on my kick track because there was 'bleed'. That might be a good solution for you if you can get it to sound good.

thomachine · Posted: Tue Mar 06, 2012 3:52 pm Post subject:

Ill play around with different gains next time recording something. As i said, its not that loud, and doesnt bother me that much.

It seems like everything is as it should then.

I think i have been "spoiled" with softsynths and digital synths over the years, so i have been used to no noise at all. smile

Thanks for the help guys!

matttech · Posted: Tue Mar 06, 2012 4:02 pm Post subject:

oakley vcas i have - no bleed at all
stg vca - no bleed
a132-3 - CEM version (TINY bit of bleed, virtually iNaudible)
a132-3 - SSM version (newer one....small amount, but audible)
malekko vca - none

mojopin · Posted: Tue Mar 06, 2012 4:34 pm Post subject:

Ok further testing. Same amount of bleed using uvca, .vca, 4mx or hex. It is very little and everything is cranked to hear it! But, send the signal to the cv input and listen out on another channel and the uVCA is clear as day! The hex exhibits some and the other two not at all.

intellijel · Posted: Tue Mar 06, 2012 6:18 pm Post subject:

mojopin · Posted: Tue Mar 06, 2012 6:38 pm Post subject:

intellijel · Posted: Tue Mar 06, 2012 6:46 pm Post subject:

A huge weakness of the Euro format is that the power supply does not use a star grounding scheme.

Also analog VCOs (and Digital clocks) generate tons of high frequency harmonics. High frequency signals behave differently than low frequencies and they can kind of "pour" out all over the place. With clever grounding schemes, smart pcb layouts and well placed chokes you can eliminate a lot of the issues.

With busboards, patch cables (with grounds on them) and a big mix of modules in a rack you are creating a fairly complex system designed by many different people so there are going to be some tradeoffs when it comes to noise issues.