TT mains hum

At least that's what I assume it is. What happens is that I get a very faint hum through the speakers when I select the TT on the preamp. However, it gets louder as I move the arm away from its resting position and towards the edge of the record. This happens irrespective of whether either the TT or the power supply is switched on. I assue it has something to do with earthing of the arm (OL RB300) or the phono stage (Creek OBH8). Disconnecting the arm's earth cable from the phono stage doesn't make things better or worse. Any guesses as the the cause or the solution?

John

 

i have the same thing wsith my no expense spared top of the range, (project expression cough cough)

regardless of whether the player is plugged in, switched on, platter in place or not. so it has to be cable dressing based..

 

Try connecting the earth to the amp and not to the phono stage, cured mine.
Geo.

 

some carts are more prone to picking up motor electircal hum, does it do the same when the TT is off? When it is off it will only be the passively live arm connected, so if it continues ,then check the earthing / wiring. If not an off board power supply may help but I suspect as the arm moves across the platter it is getting nearing the motor and picking up interference.

 

It does it when the motor is off and when the offborad motor (michell VC) power supply is powered down

 

Tried this too (to the preamp earth). No joy

 

maybe you have an earth loop from the mains, i.e. if all items are earthed then it will create a loop causing hum, the only thing you did not mention is the t/t/ psu earthed to the mains ? nando.

 

Yes the TT supply is earthed via a regular 13 amp plug. However, it has just occurred to me that the phono stage is powered from a wall-wart so I'm not sure how that will be earthed (if at all)since the mains plug has a plastic 'pin' in lieu of an earth pin. Likely source of the problem?

 

the phono stage is being grounded back to the amp via the ic's ....

is it definately a mains hum ?

have you checked that the phono stage is sited well away from your amp[valve ?]

 

It could be an earthing problem between the arm and the motor, turntable chassis. Make sure both part are earthed together. Does the hum decrease when you touch the turntable spindle, chassis etc.?