Motor noise only at 100 ohm impedance

[Narrowfellow]

I'm wondering if anyone has encountered anything like this. I'm running an Audio Technica AT33MONO cartridge on what's essentially a Rega RB300 tonearm, into a PS Audio Stellar phono preamp and then into my Leben CS300F. A wonderful feature of the PS Audio is that you can change the loading via remote. While listening to different settings, I've discovered that I get fairly loud motor noise when using the 100ohm setting. All other settings are dead silent. I just recently started using this table/arm combo with the Stellar so I don't have any other cartridges to compare, but when on the SME table with Koetsu, Benz, or Sumiko carts, no problems at all. Just a weird combo, or?

 

[Balle Clorin]

Turntable is? Any difference with position on platter?

 

[analogsa]

I've discovered that I get fairly loud motor noise when using the 100ohm setting.

This sounds very strange. Are you certain the noise is caused by the motor or is it just humm? How does a stereo cart behave? It should relay more motor rumble.
Does the noise disappear when the motor is stopped?

 

[microstrip]

As far as I remember the Rega RB300 does not have a separate ground wire - the arm is grounded using the left channel ground wire. If you use a mono cartridge you are probably creating a ground loop somewhere with maximum current with a low load resistance.

 

[Narrowfellow]

The table is a Linn LP12 with an Origin Live DC motor in it. Might be a grounding issue as @microstrip mentioned, but the tonearm is rewired with a ground wire. Noise only comes out of the left speaker and only when the phono preamp loading is set at 100ohm. Not a big deal because I prefer the sound at 200ohms anyways -- but still an odd, subtle, quirk. Thanks for chiming in guys.

 

[microstrip]

The table is a Linn LP12 with an Origin Live DC motor in it. Might be a grounding issue as @microstrip mentioned, but the tonearm is rewired with a ground wire. Noise only comes out of the left speaker and only when the phono preamp loading is set at 100ohm. Not a big deal because I prefer the sound at 200ohms anyways -- but still an odd, subtle, quirk. Thanks for chiming in guys.

Ok, maybe you are getting a ground loop because you have a double earth path - do you still get this noise if you disconnect the ground wire?

 

[Narrowfellow]

Nope, everything is worse on all settings if I disconnect the ground wire.