Nude Turntable Project

Thuchan,
Don't get me wrong.......
The Raven AC-2 is an excellent turntable providing very stable speed control and superb analogue performance when set up correctly.
It has audibly kept level with the TT-101 until this last 'nudie' change I have made.
And in my 35 years experience listening to all the best turntables I could access.....the TT-101 is simply the best.
The fact that I have extracted a performance level from the Raven that is so close......speaks volumes I think?
I will not be selling the Raven :-)

I guess Syntax might say that he is not surprised that you prefer the TT101 to the Raven for deepest bass response. I've never yet owned a BD tt with a platter that would meet Dertonearm's standard for mass, so I have no opinion (and in fairness, I may be misquoting the minimum mass, but the parameter "35 lbs" sticks in my mind). I did at the time take some issue with his explanation for the finding, which was not solely based on rotational inertia.

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.