[sdiy] spring reverb & hum

[Richard Wentk]

At 23:54 13/11/2002 +0100, you wrote:
>Hello
>
>My Doepfer A-100 Modular's spring reverb picks up a terrible amount of hum
>from the transformer. Doepfer's only suggestion was to move the unit further
>away from the rack with the transformer in it.
>
>Any suggestions on how to make a spring reverb less hum-sensitive?

Following on from the humbucker idea - how about running the signal though 
a bare wire next to the reverb, or even through the reverb tank and using 
that as a hum pick up? Then subtracting that signal from the reverb output? 
You'll probably need to trim it to get it right and perhaps add some 
filtering. But with a bit of tweaking you should be able to get near 
perfect cancellation.

Alternatively use two reverb units and subtract one from the other. Of 
course you'll get some weird subtractive version of the different spring 
responses - which probably won't be what you want, but will sound 
interesting all the same. :)

To be honest I think the 'Just move it' reply is not very professional. 
There's no reason why a spring reverb needs to hum badly if it's designed 
properly. I'd also be worried that if I were getting that much hum from one 
module, the transformer is radiating more strongly than it should do, with 
there's a danger of getting hum within other modules too.

Richard