[sdiy] Reverb picking up power supply hum

[HARRY BISSELL]

Its almost a sure bet that you have magnetic flux leaking from the
power supply transformer and getting into the pickup coil in the
reverb spring.  Move or re-orient the spring, get it farther away
from the transformer, or shield the spring and/or the supply with
ferrous metal (steel, better iron... or better still Mu-metal) Places
like advanced magnetics sell mu-metal foil. Its REALLY REALLY good for this
and has a really really high price tag to match the performance.

You might consider switching the power supply transformer to a toroidal
type, which radiate a much smaller magnetic field.

H^) harry


----- Original Message -----
From: Scott <Scott at scottwick.com>
To: synth-diy at dropmix.xs4all.nl
Sent: Fri, 24 Apr 2009 15:39:23 -0400 (EDT)
Subject: [sdiy] Reverb picking up power supply hum

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.

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