[sdiy] Reverb picking up power supply hum

[Ian Fritz]

Have a look at this stuff for modern magnetic shielding.

http://www.lessemf.com/mag-shld.html


At 05:22 PM 4/24/2009, HARRY BISSELL wrote:
>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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