[sdiy] Building the ASM-1 Noise Source

[Magnus Danielson]

From: mmanard at columbus.rr.com
Subject: [sdiy] Building the ASM-1 Noise Source
Date: Mon, 20 Dec 2004 17:28:35 -0500
Message-ID: <3df67b3e01f7.3e01f73df67b at columbus.rr.com>

Michael,

> I breadboarded the ASM-1 Noise Source:
> http://home.swipnet.se/cfmd/synths/friends/stopp/asm1ns.pdf

http://rubidium.dyndns.org/~magnus/synths/friends/stopp/asm1ns.pdf

is the new URL for that. The SWIPNET site could disappear at any moment they
feel like it. Everyone should redirect their links to the Rubidium site.

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

You have a fair amount of gain in there. Any small pickup in the early stage
will be fairly well amplified. Check what you can do to lower it. It may be
conducted in, but it could very well be a magnetic or static pickup. Avoid
big loops (for magnetic coupling) and avoid wires far away from ground wires.
Actually, a small metallic box could be the solution to the static pickup, but
only to a small degree the magnetic picup.

Cheers,
Magnus