Fwd: [sdiy] When building a White Noise module has anyone ......

[Rykhaard D.A.M.I.A.N.]

---------- Forwarded message ----------
From: Rykhaard D.A.M.I.A.N. <rykhaard at gmail.com>
Date: Jan 10, 2006 1:00 AM
Subject: Re: [sdiy] When building a White Noise module has anyone ......
To: "jays at aracnet.com" <jays at aracnet.com>

On 1/9/06, jays at aracnet.com <jays at aracnet.com> wrote:
>
> Rykhaard,
>
> This sounds like the noise source maybe putting noise on the power supply
> or ground busses. This could transfer the noise to all modules in the system
> and cause things like VCAs to put out noise without anything hooked up.


That IS, what has happened.  Without the noise output hooked up to either
the VCF or the VCA, I could still hear the noise at a low level.
When I removed the 2nd opamp's 100K (1 to 100 amplifier) resistor and
replaced it with a 100K pot, I got rid of the problem of the noise
transferring to the other modules, when it wasn't hooked up.
I noticed on the scope, that at full amplification, the noise was clipping
at certain peaks, as well.
Turning the amplification knob down, to about 1/3, got rid of any clipping
and completely removed the noise from the circuit.
Hooking up the noise output then, to the VCF, which had it's output hooked
up to the VCA, seemed to allow normal operation.
Still some minor concerns with it though, with the VCA's Main output still
having the 'on' portion, between 10am and 2pm. :(  Outside of this Noise
module, the VCAs function normally ......

You may want to put more filtering between the noise source and the filter.
> If the problem occurs when you hook up the filter you may want to try
> putting more filtering between the filter and power supply. Typically you
> will have a larger cap 10uf-47uf and a smaller cap 0.1-0.01 between each
> rail and ground. These MUST BE BETWEEN the power and module. DO NOT run
> power to the module, use it and then filter it.
>
> Right: PS->Caps->Load
> Wrong: PS->Load->Caps
>
> Good luck.
> Jay
>

Aye.  Standard procedure. :)  I've used 100uF caps on each of my +/- inputs
almost since day one in 1992. :)  (This is my 4th or 5th working noise
module and the first time I've ever had a trouble like this. :( )

Filtering, seems to be the trouble.  For the dual opamp of the noise module,
I've only a 0.1uF at it's + supply pin; the caps for it as required, and the
100uF's at the power input of the entire board itself.

Thanks to help from yourself and Harry, following your message - it'll get
figured out. :)
--
Take care,
Warmth and Peace,
Ryk

http://deathlehem.bravehost.com/damian.html - D.A.M.I.A.N.;s webpage - Jan.
1006 update

--
Take care,
Warmth and Peace,
Ryk

http://deathlehem.bravehost.com/damian.html - D.A.M.I.A.N.;s webpage - Jan.
0406 update
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