Nude Turntable Project

I received a sheet of mu-metal magnetic shield today and installed it in my TT-101. Here is the Before image showing the interior damped with automobile damping sheets. Here is the After image showing the mu-metal sheet cut into shape and placed over the motor. It is not grounded, nor is the turntable.

The result is that the magnetic field has moved away from the tonearm arc area of the platter over to the opposite (left) side of the platter. It is also more intense on the left side than it used to be on the right side but I think that it doesn’t matter because it doesn’t reach the cartridge. Mu-metal can only shield an area from magnetism, it cannot destroy the field. It is like squeezing a balloon – the air just moves to a different area in the balloon.

Soundwise, I haven’t done any blind testing or even playing an album side with it and then playing the same side without it – which is how I like to do it. But, I did play a few cuts on a few favorite albums and was (perhaps deluded into) hearing a better audio image and clearer notes and lyrics than I expected. I got that dumb grin on my face that I get when my rig sounds great.

An easy tweek that I (almost for sure) believe in.

Gary

EMF Measurements

Using an EMF Field Tester, range 0.1 - 200m Gauss I found the following measurements interesting.
Highest EMF emissions from vacuum tube preamplifier.
2" above the power supply 23m Gauss
2" above the tube circuitry 8m Gauss
15" to the side of the preamp 0.1m Gauss
15" above the preamp 3-4m Gauss.

The conclusion is that it may be better from an EMF view to place the equipment beside the TT and not underneath it.

As regards to the magnetism tests, on my Final Audio Parthenon, which uses Copper mat, Aluminium platter, gunmetal & SPZ bearing housings and base, there is no magnetism measured at all - none.

Halcro, could it be that you enjoy the Victor more because of its magnetic personality ? Magnetism in ferrous metals can be masked through the use of chrome plating. Some of the Japanese high end tube manufacturers use this technique of a chrome plated and painted steel chassis because the common alternative, aluminium, induces hysteresis distortion in the electrical signal when aluminium is placed near an electrical flow.

I have seen the Technics SP02 DD motor in a cutting lathe situation; the motor was mounted about 2 1/2 ft below the cutting head and the platter was 50kg. This is probably the way you should build a DD. The alternative would be to convert your DD to a thread drive and mount it all in a non magnetic chassis.

Final suggestion for the Victor owners who want to dispense with the flimsy cover, why not build a faraday shield but mount it to the shelf, not the TT. This will provide shielding and minimise resonance.

Lewm,
Syntax despises DD turntables and Idlers and eschews the qualities displayed by the big Caliburn belt-drive.
He also abhors MM and MI cartridges so crediting him with any knowledge of the TT-101 is like mistaking him for a man of discernment?

Dover,
Did you miss the point that with the pigskin platter mat in place....there was no magnetism at the mat nor the vinyl disc?

Dover, Did you mean "EMF" or "EMI"? The discussion has gotten a bit confusing with the interchangeable use of the terms "EMI", "magnetism or magnetics", and "electromagnetics". Different manifestations of the same phenomena but with different consequences. I think of "EMF" as "electromotive force" = Volts. Units would not be "Gauss", I don't think.

Of course you would measure no EMI (or EMF) near the chassis of your belt-drive, where the motor is way outboard on the other end of the long belt. That is to be expected. Do you think the magnetic field or the EMI measurable in the vicinity of the platter of some DD turntables is damns them all, as a class? I am not even sure there is any consequence to it, and if there is, many have shown that the fields can be shielded.

Halcro, I have no bone to pick with Syntax, but I agree on the observation that he and a few others who are countrymen to Thomas Woschnick do seem to revile his Raven turntables to an inordinately passionate degree. It seems strange at times. He did not insult the TT101 so much as he did insult the Raven. Did TW kick someone's dog?