At the moment I am doing some retouching on old modules and I would have a question about 2 white noise based modules (CMOS noise Bell and Snare / Tom) which, even when the module is not triggered, have a slight noise leak at the output.
Should I add a small capacitor on the jack out to filter this frequency
And if that can solve the problem, you think a capacitor of what order of value would do
thank you in advance
I think I recall similar behavior when I tried breadboarding the bell circuit. It has a very minimalist “VCA” consisting of a couple diodes and a resistor, and I guess it was letting sound through even when the CV was zero. Or maybe the internal envelope generator wasn’t quite going to zero, but when I substituted a 4066-based “VCA” it worked better.
If what’s leaking out is just a low level version of the desired sound then a frequency filter isn’t going to be the best solution — if it’s effective in cutting the leakage by 90%, then presumably it’ll cut your “on” signal by 90% too.
First (and not great) idea that comes to me is a pair of diodes, antiparallel, in series with the output. If you can measure the peak to peak voltage maybe you can find diodes (Schottkys maybe) whose forward voltage matches that. They’ll cut your “on” signal too, but by a fixed small amount instead of a large percentage. I think you’ll want a pulldown resistor after the diodes, too.
It’s not a great solution, it’ll add some distortion, but not that much for square waves, I think, and anyway maybe in this context you won’t care. I’m sure there are more sophisticated approaches that would work better, but I like the irony of two diodes and a resistor fixing a problem caused by two diodes and a resistor.
thank a lot …
DIY modules can often benefit from power switches…
Just to come back to that, after a few hours of various tests of all kinds, the problem disappeared a few times, I understood that when I tested it alone the noise disappeared, the problem came from the proximity of these 2 modules, I placed another module between the 2 and all the silence I dreamed of was there !
I had already heard about the module placement problems between them, but more with certain digital module