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Doepfer A-130
MUFF WIGGLER Forum Index -> Fractional Rack Modules  
Author Doepfer A-130
I'm pretty new to modular synths an I'm puzzled by the behaviour of my A-130 module. Maybe some of you veterans can shed a light on things. hmmm.....

I mainly use the A-130 for audio, however, when I feed an envelope (Doepfer A-140) in the CV input (CV1) I will get an audible 'plop' sound when the envelope opens. It's not noticeable when dabbling with bass sounds, but when I tried to make a high-hat yesterday it was highly annoying (I needed a high-pass filter to get rid of it.)

Things I tried:

Adding attack to it get rids of it. The faster the attack, the more prominent it becomes.

It's present even without any signal at the audio input of the VCA. So I'm pretty confident the VCA is at fault here.

A frequency analysis shows a huge bump at 30Hz falling gradually over the spectrum (up to 1KHz) (I should have taken a screenshot)

It's stays when I use a headphone on the VCA's output. So it's not something coming from the computer.

Things I haven't tried yet:

Decoupling all other modules and see if it stays. I don't think this will solve it, but I'm going to try it anyway. Might be some other module misbehaving somehow.

I have the D-100 DIY kit as power source ( However, this has no ground (it's an external AC convertor), maybe providing a ground wire might solve the issue (how do I do this? regardless of this issue, I do feel it should be properly grounded.)

I use a mini-jack to mini-jack to the computer for now, this is a stereo jack. That might be an issue. I don't get it to the studio before thursday, there I can hook it up with the right cabling to the mixing desk.

Maybe the module is faulty?

I'm planning on getting an A-132-3 (because 1 VCA is just not enough). However I don't want it ti have the same issue.
You should have posted this thread in the Euro sub-forum.

I doubt the VCA is faulty but guess you're using a fast envelope. This often leads to 'pops' and 'clicks' when the audio wave is at it's peak, while the VCA suddenly opens.

Try a longer attack time or sync the VCO to the same trigger.
Your VCA is not faulty most probably, it's a common problem.
Have you tried setting the switch on a-140 to Medium or High settings? You can also try smoothing the envelope with slew limiter, works great for bass sounds.
ahw.. fuck.. wrong forum (am I really this stupid). I'll repost it in it's rightful place and see if this can be deleted.
You could always contact Cynthia and see if there are any in stock and ready to go.
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