[sdiy] Building the ASM-1 Noise Source

[harrybissell]

Hi Michael nil-x

One major issue could be your selection of noise transistor. Some give only a hint of noise...
and allow massive amounts of hum that would be masked by a proper level of noise.
I had this problem with the MacDonald MiniModular when I first started it up.

Another issue might be proper decoupling of the drive to the noise transistor itself. Sometimes
you need an RC filter on the supply...

Last trick... use a couple of 9V batteries to power the circuit, eliminating the power supply
If the hum is gone, its the supply...

H^) harry

mmanard at columbus.rr.com wrote:

> I'm using PCB Proto soldered. I did check for shorts and checked for bad solderjounts with a DMM. The IC's are not in sockets, just soldered in. There is also an issue when I put my finger anywhere near the 4.7uf cap and transistor it makes a godawful buzzing noise. I do have some longish (3 in or so) wires that i'll try and shorten and I'll plug it in away from other electronics to check it out.
>
> - Michael nil-x
> - Pressure : Penetration
>
> ----- Original Message -----
> From: jays at aracnet.com
> Date: Monday, December 20, 2004 6:01 pm
> Subject: Re: [sdiy] Building the ASM-1 Noise Source
>
> > 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
> >
> >
> >