Turntable speed accuracy

Lewm, The Artemis is an interesting design. I have not heard one yet.

I had hum caused by the motor on a VPI Classic and a LP12. The Classic's motor is on the front left. Maybe if the motor was placed in the rear it would have been better. The LP12 had the motor and power supply under the platter. Could be if I had an outboard PS like a Lingo it would solve the hum. I was not using a Grado. I am sure there are TT designs that have the motor close that don't have hum issues. Just a matter of being well designed.

I have a SP10 mk2a now and experience no hum with the same carts. Sorry if all of this is off the topic of this thread.

Sarcher30: "Unfortunately bringing the motor closer to the platter also brings it closer to the cartridge as well. Which on the TT's I have had with that arrangement caused hum on most of my cartrides. There may be some TT's that sheild the motor well enough to pull it off."

Perhaps you can try grounding the motor housing?

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Lew, are you saying that you was able to get the Lenco dialed in with the Walker to allow no drift with the Timeline.

Sarcher, What is the evidence that the hum is (or was) due to the motor/cartridge interaction?

Banquo, I have some knowledge but not much skill when it comes to the electronics of either a motor controller (for BD) or a drive system for a DD tt. If I have a problem, I rely upon Bill Thalmann to deal with it, at my expense. But I do have the good fortune to live within 30 min of Bill's shop.

Halcro, I'm not sure I agree with Peter on this one. Our model 208 has the motor quite close to the platter (opposite the tone arm; there are no hum problems even with Grados). However the 208 uses a motor that would easily qualify as a flywheel in its own right. Keep in mind that in a belt drive, cogging is almost a non-issue due to the rotational speed of the motor, and then really only applies to DC motors for the most part.

AC motors are not particularly prone to cogging effects. The best tape drives all have direct-drive capstan motors, usually AC, and they often have rock-solid speed stability that turntables struggle to match.

The Empire that our machine is based on was one of the most speed stable made for quite a long time. Julian Hirsch complained in one of his reviews of it that the speed variation was "buried in the noise" of his instruments, making an exact number difficult to gauge (although Empire did publish specs at the time). Sounds to me like he could have used a Timeline...

I've played with a variety of belts on the machine. Interestingly, even mylar variants sound exactly the same. Its my opinion that if the belt alters the sound then there is a problem in the drive system somewhere.

So I don't buy the idea that drag in the bearing results in speed stability at all although it would not surprise me to find that some designers may have created this story for reasons of their own (obviously the 208 flies right in the face of Peter's comments). OTOH I don't doubt that the belt-drive Thorens had some problems! I think that is why the earlier Thorens are the ones people are looking for.