[sdiy] DIY TR909 : noise !

[Scott Gravenhorst]

This is quite likely not your problem, but who knows...  I had a problem
with noise that I thought was coming from some instrument I had plugged
into my mixer.  It turned out that one channel of my mixer started spewing
noise.  When I moved the instrument to a different channel the noise
stopped, but only after I turned the level on channel 7 all the way down,
it was noisey even with nothing plugged into it.

<jschmitz at schmitzbird.de> wrote:
>Hi,
>
>for clarification : of course the noise level is set to 0, and I also =
>tested the circuit with not inserted noise-generating opamps 7 & 8. No =
>change, the hissing noise is there. As I said, it is a very very low =
>noise level, but it is audible and I dont like it.
>
>greetings, Joerg
>
>
>
>>at last I have managed to built my own TR909 - bass drum pcb. It works =
>prettty well (see >http://www.analog-synth.de/synths/tr909/tr909.htm for =
>details), but I found one problem :
>>the output is a bit noisy. You can hear a little hissing noise, which =
>seems to correspond to >the envelope and therefore VCA activity of the =
>VCA between the output amplifier and >distortion diodes (controlled by =
>"decay").
>
>>What would you suggest to eliminate that (not very loud) noise ? (Of =
>course, this is not the >noise of the noise generator, bleeding through =
>somehow, this is tested...)
>>Another opamp for the output-amplifier ? Something better than the =
>TL072 ? Something >better than the BC549 for the VCA's ?
>
>

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