Thorens Turntable Hum

I've got a couple of Thorens turntables -- TD145 and Thorens TD160 MkII. The grounding is through the audio cables and I'm having problems with hum. Anyone know how to fix this?

 

What are you using for a Pre, does it support an indipendent ground, and does the Thorens have a ground wire?

Also, what cart are you using and did you check to make sure the connectors on the pin-outs on the cart are kosher?

 

I've got a McIntosh C40 preamp that has a ground terminal. The cartridges are older Grados -- G and G2. Neither of these Thorens models have a ground wire - they are grounded via the right audio cable. Pinouts to the cartridges seem to be fine.

I've found that when it starts to hum I can mess around with the cables a bit and the hum seems to go away. I'd just like to have it stop for good Maybe the proper question is,"How can I DIY a ground cable?"

Also, any suggestions for turntable isolation?

 

Try screwing a wire to the metal chassis of the turntable and then attach the other end of the wire to the ground on your McIntosh.

 

Some Grado cartridges are known for humming even when they are "well grounded". If Tullman's solution does not eliminate the humming completely, trying a different brand may help.

 

Yup, Grados are unshielded and will pick up hum from the motor. One usually hears of this problem with Rega and ARs, though. I used a Grado + Thorens and didn't have a problem with hum.

 

I tried Tullman's solution (Thanks Tullman!) but it still hums. However, I CAN get it to stop making noise if I mess with the wires where they connect to the RCA jack. Maybe another cartridge is the only solution.

 

I had the same problem with my Thorens TD160 Mk II, only it was with a Shure V15 Type 4 Hyperelliptical cartridge! I had to take it to a dealer and have him reterminate my phono cables. It fixed the problem licketty-split! Apparently there was a short in the right channel termination causing the hum!

 

Chuck,

The turntable's motor is not the only source of humming. A nearby transformer can induce humming as well.

My TD 160 Super shares the same manual with the TD 160 MkII. Figure 7 on page 8 shows a separate ground wire to "be attached to the grounding screw chassis at the chassis of the amplifier" - metal to metal. Did you find a good metal contact for the ground wire? Also on the same page, Figure 8 shows the aforementioned bad position of the turntable (rotated 90 degree clockwise) with the cartridge being right above the transformer of the amp.

You said "they are grounded via the right audio cable". On Section 7 on page 19, it is stated that "The second contact on the green lead is connected to the bare pin on the inner side of the cartridge wand to establish a ground connection between the shield of of the right channel and the tone arm." Is the green lead connected as instructed?

If you can remove the bottom cover, trace the phono cable to the underside of the tone arm base. You may find a grounding screw. My SME 3009-R has one, so should the stock Thorens on your MkII and all the other tone arms - the blue (L-) and the green (R-) tone arm leads have got to be connected to something! That's the best contact point for this end of the ground wire.

If none of these works, it will be either the tone arm wires or the cartridge you need to troubleshoot.

 

D'oh! That reminds me: the last time I had a hum problem (Linn + Grado), my cartridge was picking up hum from the power supply for my DI/O.