I was thinking about this hypothetical problem this morning in the shower. It seems to me that the cartridge itself might provide a low-pass filter that would prevent any RFI emanating from the electronics of a DD table from entering the downstream audio system, since few cartridges can respond to anything much above ~50KHz. (As far as Grado cartridges inducing hum in conjunction with an AC tt motor, that is an entirely different problem.) Is there any concrete evidence that RFI (that's very high frequency hash, not 60-cycle hum) is a real problem with DD tables that place complex circuitry below the platter? For that matter, the (aluminum or other metal) platter itself would provide something in the way of a shield, altho imperfect. Is this a cure without a disease?
Belts vs Direct Drive and correcting experiments
I am intrigued by the belt drive vs direct and idler drive debate.
I happen to have an amazon model one - total antithesis of a direct drive deck insofar as it is:
high mass platter
low torque motor - albeit battery powered dc
a 'thin string' as opposed to even a belt.
I am now in the process of restoring an EMT 950.
I know Albert Porter has had great success with the Technics mark 3 - which replaced a walker proscenium in his system.
David Price of Hi fi world had a shoot off between a trio L07d and a new Michell Gyro - the results went something along the lines that the Pace rythm and timing were way better in the trio, and the tonal colourig and image size was better/more pleasant with the trio.
I have had a look at a page dedicated to the trio L07d that says that the image problem tonal colouring problem can be largely addressed by the use of a sheet of copper alloy of sorts to get rid of EMI and another sheet of a cloth like material for RFI interference.
I personally think that the RFI EMI problem may well be a problem with most direct drive decks due to the fact that the motor is directly below the platter. In pursuance of this I am convinced that all direct drives can benefit from such a modification.
With my own EMT 950 - that has both a direct drive motor and a massive steel chassis with an inboard phono stage - I am convinced that such shielding would go a long way. To that end i am thinking about whielding all the electric phono stage parts etc, and also possibly the motor.
I have also discovered a spray on shield that uses an acrylic base that i may well spray onto the steel chassis before i paint it with epoxy paint.
On the belt drive front I am not sure i can do much more with my deck.
I look forward to the discussion on this topic
I happen to have an amazon model one - total antithesis of a direct drive deck insofar as it is:
high mass platter
low torque motor - albeit battery powered dc
a 'thin string' as opposed to even a belt.
I am now in the process of restoring an EMT 950.
I know Albert Porter has had great success with the Technics mark 3 - which replaced a walker proscenium in his system.
David Price of Hi fi world had a shoot off between a trio L07d and a new Michell Gyro - the results went something along the lines that the Pace rythm and timing were way better in the trio, and the tonal colourig and image size was better/more pleasant with the trio.
I have had a look at a page dedicated to the trio L07d that says that the image problem tonal colouring problem can be largely addressed by the use of a sheet of copper alloy of sorts to get rid of EMI and another sheet of a cloth like material for RFI interference.
I personally think that the RFI EMI problem may well be a problem with most direct drive decks due to the fact that the motor is directly below the platter. In pursuance of this I am convinced that all direct drives can benefit from such a modification.
With my own EMT 950 - that has both a direct drive motor and a massive steel chassis with an inboard phono stage - I am convinced that such shielding would go a long way. To that end i am thinking about whielding all the electric phono stage parts etc, and also possibly the motor.
I have also discovered a spray on shield that uses an acrylic base that i may well spray onto the steel chassis before i paint it with epoxy paint.
On the belt drive front I am not sure i can do much more with my deck.
I look forward to the discussion on this topic
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- 9 posts total
- 9 posts total