[sdiy] Building the ASM-1 Noise Source

[jays at aracnet.com]

Michael,

You never mentioned in you are using a PCB proto-board (solder) or an 3M/El type proto-board (push in). The 3M/EL boards are nortorious for bad connections and being flaky.

Go though and check your grounding. A lot of times excessive hum is caused by grounds not hooked up or not hooked up correctly.

ICs sockets are another place that bad connections can happen.

Like Magnus said to. Keep wires short and away from things that could act as 'noise sources' (other than the one you're working on).

Might get the ohm meter out and give a quick check to make sure everything is connected up properly and you do not have any high resistence connections.

Jay S.


Magnus Danielson <cfmd at bredband.net> wrote :

> 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