Spring Line Hum

[J. Larry Hendry]

From: Paul Perry <pfperry at melbpc.org.au>

I did hear once of someone using 2 lines next to each other & out of phase
as a kind of 'humbucking' setup. Dont know how successful this wd be,
quite apart from the fact that combining signals from 2 very similar
lines might have some weird byproduct.
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The PAiA spring reverb uses this design.  I built one and mounted the tanks
on top of an aluminum shelf so that the tanks are nearly 100% enclosed.  The
shelf allows the whole thing to fit behind a 1U 19" panel too.  I can't say
how the hum factor compares to single tank designs as it is the only spring
reverb I have.  I can only report that it still does have some hum when the
output is connected to an amp without any signal and cranked to a high
level.  On the other hand, when mixing an appropriate level of spring back
into the original signal (the way I normally use my spring), the hum level
is undetectable in headphones.

Larry Hendry