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In Reply to: RE: Thank you, Penguin ... posted by Tube747 on September 25, 2016 at 10:46:08
The improvement when I added the 2nd motor was significant but what that BIX TT delivers may not be as good as it can be. It depends how a DC motor works.
With an AC motor, when you have 2 motors and 2 belts driving the platter/subplatter, you need to have a slight difference set up between the 2 motors (call it a 'phase difference'). Essentially, AC motors 'cog' - so there's in effect a period where the motor applies rotational force to the platter ... and a period when it doesn't. You need the 2nd motor to be applying its rotational force during the period which the 1st motor is not - so you need a pretty sophisticated speed controller (I am using a prototype of the "Number9").
If a DC motor doesn't do this but simply applies its rotational force evenly - then the BIX kit will be fine (from that PoV).
Andy
Follow Ups:
Hmm I agree. However I worries the noise generated by the AC motor will transfer to the bearing.
I come up an idea after talking to my friend. Unlike the BIX with rectangular chassis, I can have the acrylic chassis made in Big Arrow shape, and motor positioning on each corner, the Cirkus bearing is indicated by purple circle, the star will be where the tone arm goes.
That's why AC motor get a very good chance to transfer the noise to the bearing under this arrangement.
Mounting the motors on the same chassis as the bearing is a baaad idea, IMO.
On mine, each motor is bolted to the underside of a approx 4"x4" earthed steel plate - these plates are bolted to the top of 3"D brass cylinders (very heavy).
The cylinders don't rest on the perspex base of the TT (which the brass pods under the springs do) - there's a hole cut in the perspex, so the motor pod rests on the benchtop below and doesn't come into contact with the sides of the hole. So the motors are entirely separate from bearing.
Are you sure DC motors don't have any vibration (for your "arrow chassis")?
Andy
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