[78-L] turntable hum mystery

[Steve Williams]

Hum is almost always caused by having two different paths to ground.  Is it
amplifier and integrated unit with radio, or amp connected to a radio, that
is itself connected to cable or an antenna?  The two grounds would be the
wall socket pin and the earthed cable/antenna connection.  If there IS only
one ground point, and it's a separate phono preamp, then try connecting the
cartridge ground wire to the amp instead of the preamp.  Also, last resort,
separate the turntable metal parts from the electrical ground of the
cartridge, connect cartridge ground to preamp and turntable chassis to amp,
which is then grounded to the wall.  START with making sure there isn't more
than one path to Earth ground.

Steve Williams  ..

Message: 2
Date: Thu, 08 Nov 2012 16:46:10 -0600
From: "neechevoneeznayou at gmail.com" <neechevoneeznayou at gmail.com>
Subject: [78-L] turntable hum mystery
To: 78-l <78-l at klickitat.78online.com>
Message-ID: <509C3632.1030800 at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Listers,

Last time I posted about hum on my turntable, it was solved by checking the
ground connection. It was loose, and tightening it made a huge improvement.

Later I was thinking I was hearing much hum from the records. Surely they
didn't record that much hum in so many records did they? Upon further
investigation, it appears not to be from the records. It is only when the
table is on and the stylus in contact with the record. Lift the stylus even
the tiniest bit and the hum goes away. Turn the thing off, even with the
stylus on the record, and the hum goes away.

So how is the hum getting into the system? Neither vinyl or diamond are
conductors of electricity. So I've ruled that out. Bad p.s. caps giving off
EMR that the cartridge is picking up? Seems unlikely, in that picking up the
stylus even the tiniest bit causes the hum to cease. If the leak were in the
air I would expect the hum to remain as long as the cart was within a
certain proximity.

Whaz goin' on here?
--
Joe Salerno