[sdiy] x0xb0x background noise problem

[Amos]

Wow, your own x0xb0x *doesn't* do this?
Having built two so far which both have this problem, I thought it was
endemic to the breed.
It is (somewhat) encouraging to find otherwise, but it makes solving this
problem even more important... I am about to build a third b0x (for an [AH]
listmember who is not so DIY) and would like to ensure that it does not
click & pop, especially when used as a filter for external audio.

The following link has all x0xb0x schematics in Eagle format as well as .jpg
snapshots for the Eagle-less:
http://www.ladyada.net/make/x0xb0x/download.html

any clues or guesses from the synth community?

here also is a virtual scope trace of the clicking, to compliment the mp3
posed by Louis:
http://bulldog.unca.edu/~azgaynes/envelope_click.jpg

thanks!

Amos (and other x0xers who are also very interested in solving this problem)

On 12/13/05, Louis van Dompselaar <louis at dompselaar.org> wrote:
>
> I've already posted this to the x0xb0x forum but I think there's
> a lot more experience out on this list ;-)
>
> I have just finished building #149 for someone else (after doing my own)
> and it worked first time round
> (http://www.dompselaar.org/x0xb0x/149/x0x149_02.mp3) but on closer
> inspection there is a constant background noise in there. It also
> amplifies VR8 (volume) slider movement. I tried a replacement for VR8
> (different type and brand) but that sounds exactly the same, so it
> doesn't seem to be related to that pot.  The noise is present on VCA
> output anyway. I can actually see it on the scope.  If I get the time
> I'll try and trace it back down.  I *think* the VCO and VCF were clean
> when I first tested these in isolation.
> Power lines are clean, at least in the ranges my scope can manage.
>
> I would've just put this down to it being old circuitry, but since my
> own b0x doesn't have this (it's actually extremely noise-free), it must
> be something else.
>
> Here's the background noise (much amplified) with me moving VR8:
> http://www.dompselaar.org/x0xb0x/149/x0xnoise.mp3
>
> Any obvious things that come to mind that would cause this?
>
>
> Louis
>
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