[Phil Allison[_4_]]

Mike Rivers wrote:

-------------------

Indeed, this is true. Switching supply noise does not sound like a hum.
Distinguishing hums, buzzes and hisses is half the struggle.

I've given a talk about that, with examples, a time or two. Most people
just say "hum" and leave those of us trying to help them out guessing
what the real problem is.


** Becomes a REAL hassle if the owner cannot demonstrate the noise to the tech but still expects instant diagnosis.

A regular customer and PA system owner began having a "hum" problem with his home stereo, so he brought me his TT and amplifier - which showed no sign of hum whatsoever.

When he casually mentioned that the "hum" even showed up on his cassette deck, I firmly directed him to make a recording and bring it to me.

When I finally got to hear the "hum" I instantly recognised it as coming from a TV set - it had the characteristic 50Hz tone of frame buzz. No wayyy, said my customer, the TV in the room was always off when using the stereo.

Hmmmmmm ....... I puts on me thinking cap.

Is your stereo set up against a common wall with a neighbour ??

He had to admit is was.

Turned out the neighbour had recently moved his TV to the opposite side of this wall, directly behind my customer's stereo.



..... Phil