[sdiy] Building the ASM-1 Noise Source

[Roy J. Tellason]

On Monday 20 December 2004 05:28 pm, mmanard at columbus.rr.com wrote:
> I breadboarded the ASM-1 Noise Source:
> http://home.swipnet.se/cfmd/synths/friends/stopp/asm1ns.pdf
>
> I built the White and pink noise portions so far.
>
> It's the first time I've actually breadboarded a circuit (as opposed to
> using a premade PCB). The noise works (kinda) but there's 60cycle hum
> that's pretty loud. I'm running on a MOTM powersupply. I assume a
> groundloop but nothing I do changes it.

Don't assume,  it'll get you in trouble.  (Don't ask me how I know this :-)

> Except one thing I notice is that if I remove the groundwire from the output
> jack the hum lessens about 50% but still pretty loud. Another thing of note
> I did was use fairite beads instead of the 22R resistors on the power input.
> When I use the 22R resistors it doesn't make noise but just makes an
> oscilalting squealing sound. I've tried 2 transistors so far.

Sounds to me like you have some other problem too.

> Well, I'm a newb so hopefully I explained well enough my issue.
> Any thoughts?

Measure the voltage at the output of each op amp.  If you don't find something 
that's pretty close to zero,  find out why.