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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
lohanimal
lohanimal OP
659 posts
 
If you do a search on google and write in kenwood trio L07 D - I think you will find the website i was looking at - this shows how to make the mate - not too difficult.

I will be reporting updates on my system as and when they are mae and posting it to this thread.

My big problem with the EMT 950 is that it has a plastic/resin platter - I might have to get some sort of spray on shield - though I am willing to take suggestions to the contrary if any good ones are made.

Lohan
lewm
13,282 posts
 
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?
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rauliruegas
13,106 posts
 
Dear Lewm: Finally something with good sense your last post.

I'm reading this thread and other ones about the DD whole subject and on this in particular and for what are my experiences with the SP-10s and DP-80/75 I don't have any problem relative to RFI/EMI problem so why to worry about with these tables?, even with my Grado I don't have any single problem on that subject.

Sometimes we are overreacting with out a precise and absolute certainty of what we are doing. Example: a man that lives in/around Arabia desert and he decide two put " chains " in the tyres of his car to " prevent " against snow/ice-road!!!!.
IMHO sometimes we are loosing our time ( with no sense ) and yes that is part of the audio " folklore ".

Regards and enjoy the music.
Raul.
lewm
13,282 posts
 
Dear Raul, If I write enough words, eventually I will make some sense. Thanks. Audiophilia is nine parts worrying about non-problems and one part solving actual problems. The vendors benefit from all ten parts of this obsession. I think now (based on some light research I just did) that the aluminum alloy platter can block RFI fairly well, so we only have to "worry" about EMI. (That's our job, to worry.)
cpk
190 posts
 
You might want to try a piece of carbon fiber cloth in between the mat and platter. That would afford some level of emi/rfi protection and also some mechanical damping. Hummm maybe I'll try in on my sp10...:-)
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