[sdiy] Reverb picking up power supply hum

[Scott]

My synth/p.s. is wired as you describe.  I only tried grounding the reverb tanks to earth as a test..  just to see if it would do anything, but that is not the way it usually is.

I know rotating or repositioning could help, but there is no room in my cabinet for changing orientation of either the P.s. or the reverb tanks (I do have two).  The open side of my tanks do share a piece of sheet metal which is on the wood cabinet, which the tanks are mounted to. (if that makes sense...)

My reverb module is also near the power supply, and that could be moved.

I just got another reply which says the output side of the tanks matters, and that I have not checked (will in a min..).  The tanks could definitely be flipped, so the right side becomes the left.

Thanks!


-----Original Message-----
From: Cynthia Webster [mailto:cynthia.webster at gte.net] 
Sent: Friday, April 24, 2009 3:08 PM
To: Scott
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Reverb picking up power supply hum

Connect the Mains Earth Ground connection from the wall plug (green 
wire) to the metal power supply chassis, and nowhere else in the synth.

Grounding for Audio jacks comes Only from the center Output pin of your 
power supply with the  + and - fifteen volt output pins on either side.

Synthesizer Audio Ground should never mix with the AC Power Mains 
"Edison plug in the wall" type ground.

Some reverb tanks are isolated from audio ground and some are not, 
check, and possibly try grounding the metal box of the reverb with
both types of ground while listening to the output of the tank/s.  If 
using two tanks try fully shielding them, with a sheet of metal between 
them,
and the orientation of the reverb tanks in relation to the winding of 
your power supply transformer are often big factors in cleaning the sound.
Try turning either the Power Supply or the Reverb Tanks at right angles 
and/or parallel to each other they can behave like the poles of magnets
in relation to each other, (and the large magnetic field of the power 
transformer can cause major mojo in the delicate HIGH GAIN recovery amp
before the output the reverb :)


Cynthia

http://www.cyndustries.com/



Scott wrote:
> If I mount my power supply (power-one 3 amp) inside my synth cabinet, I pick up some hum in my reverb (tellun neural agonizer).  I've tried grounding the power supply frame to earth.. the reverb tanks to earth..  various grounding schemes using the synths neutral line, etc.  
>
> Is there anything I can do?  There isn't a lot of room but I might be able to fit the p.s. inside a cage if that would help.
>
> I know building a little case for my power supply and leaving it external would work, but that is definitely the last thing I will do.
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
>