[78-L] turntable hum mystery

[Doug Pomeroy]

Joe,

Can you turn off the turntable motor without turning off your phono preamp?
That would allow you to rule out vibration from the motor as a source.

Doug Pomeroy
audiofixer at verizon.net


> 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