[sdiy] PAIA9700 power supply noise

[Tom Arnold]

So, was looking at a friends Paia9700.  Turns out there wasn't the issue that we
thought ( that was a cable issue ) but I did notice something sorta odd.  If you
retrigger the ADSR rapidly after a second or two the output waveform would get
some noise on it.  ( this is just VCO -> VCA, no filter ).

I poked around some more and noticed that the noise looked a lot like the noise
riding on the power supply rails and in fact adding a large cap in parallel would
increase the time needed to get the ADSR to add the noise.  

Now, I've never liked the PAIA power supply system.  Its a wallwart+voltage
doubler located on the midi/cv and everything else daisy chains from there.
Each board has an onboard set of regulators.

I'm trying to decide the best way to clean this up.

The easiest way I see is to just make a +_15v or so unregulated but heavily
filtered supply and a simple distibution board so each module can get power via a
star topology.  This is nice because it requires no module modifications beyond
removing the doubler from the midi/cv.

The other option of course is a Power One supply and remove the regulators from
each board.

I was curious if anyone else has gone down this path and if so which you chose?

-- 
 -----------------------------------------------------------------
 - Tom Arnold       -  Free Synth DIY webspace http://www.sdiy.org 
 - SynthGeek        -  "...is it a virus, a drug, or a religion?"
 - K6AET            -  Juanita Shrugs. "What's the difference? 
 --------------------         -- Neal Stephenson,  Snow Crash