[sdiy] Reverb picking up power supply hum

[Dave Manley]

The obvious solution is to replace the spring reverb with a BBD based 
reverb.

Magnetic field?  What magnetic field?

-Dave

:-)



Oren Leavitt wrote:
> Hi Scott and all,
>
> I was about suggest a toroidal transformer, too - you beat me to it 
> Harry!
> I have nixed hum problems in the past by simply using toroidal power 
> transformers in place of the old E/I frame type.
> A 3 amp toroid for a Power One would be small enough to be easily 
> oriented for best results, too.
>
> A good toroid source (Maryland, USA):
> http://www.toroid.com
>
> I buy toroids from these guys and have been very satified.
> They have toroids that would be perfect replacements in the typical 
> Power One (or any) PSUs we use for SDIY.
> Look under "Rectifier Transformers".
>
> - Oren
>
>
> 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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