Spring Line Hum

[Magnus Danielson]

From: Tim Ressel <Tim_R1 at verifone.com>
Subject: RE: Spring Line Hum
Date: Wed, 19 Jul 2000 11:47:54 -0700

> This here unrelated story might help: I have been trying to hook up an
> ultrasonic receiver to an opamp amplifier. What I got was volts of 60Hz. I
> applied different shielding techniques, and even went balanced on the amp, to no
> avail. After much scratching I figured out that I had a horrible impedance
> mismatch between the usonic pickup and the amp. A 1K resistor across the amp
> input terminals made the 60Hz go away completely. The signal is now as clean as
> can be. 
> 
> The moral of this story: The problem may not be (solved by) shielding.

Shielding is in many cases what is brougth in when you try to quick-fix
these problems. Shielding and short-curcuiting is good quick-starters just
to get a hum about the problem.

Cheers,
Magnus