A $300-$400 turntable tweak

Rockitman,

I dont know if I agree with your statement that the additional weight will not affect a magnetic bearing. Depending on the strength of the magnet, it may not be able to maintain the separation between the bearing surfaces. And with some magnetic bearings which only lessen the load on the bearing surface, not eliminate it, the extra weight could have a negative effect.

Dear Jcarr: Yes that was the meaning. Thank you. No, nothing to design , only learning about.

Regrads and enjoy the music,
Raul.

Dover:

My TT-1000 by itself has a little less mass in the platter system than stock (I needed to shave down the top of the platter to get a flat surface for the graphite mat to bond onto). Add the center clamp, and the net weight ends up pretty close to stock - not enough to warrant readjusting the servo gain.

Still, your point is valid - the servo control of a DD is typically set up with a certain load range in mind, and if the user alters the load significantly from what the manufacturer originally intended, it is a very good idea to reassess the servo gain.

I will add that many DD turntables were designed with a specific lubricant in mind. Some turntables were even designed so that the spindle functions like a self-pressurizing, self-centering Archimedes pump (similar to many PC cooling fans today), and if you change the lube, you may adversely affect the self-centering action of the pump/spindle.

I know that various DD models by JVC, Yamaha and Kenwood fall into this category. I recommend reading http://37282.diarynote.jp/200708102338400000/ and http://37282.diarynote.jp/200708111505150000/ These pages are in Japanese, so you may need to send them through a translator.

The A.R.T. graphite mat that I have bonded to the TT-1000 (using a permanently non-hardening adhesive, causing it to function like constrained-layer damping) has a recess for the LP label, and yes, I have done much experimentation with washers under the LP. Here again, I suggest using these in moderation - only as much as needed to bring the edges of a dished-up LP back in contact with the mat (or platter surface). My testing has suggested that imposing physical stress on an LP while playing it (which is what too-enthusiastic use of washers is wont to do) will adversely affect the sound.

Dover, you have a Final Audio? So do I (grin). My unit predates the Takai-era Parthenon, but is new enough to have the SPZ plinth rather than the original granite. It also has the bi-phase motor controller. FWIW, Kitamura's preferred material for mat and clamp was chrome copper rather than gun-metal. I haven't done A/B tests on chrome-copper vs. gunmetal, but based on A/B tests that I have done on gunmetal vs. other metals, my conclusion is that gunmetal isn't a material that I would care to use for sonic applications. I prefer the results with phosphor-bronze or beryllium-copper, and I imagine that chrome-copper would also work well.

cheers, jonathan carr

05-18-11: Manitunc
Rockitman,

I dont know if I agree with your statement that the additional weight will not affect a magnetic bearing. Depending on the strength of the magnet, it may not be able to maintain the separation between the bearing surfaces.

That's a given Manitunc. I can easily see the clearance between the magnetic bearing and platter on my table...I agree, too much weight so that the platter makes contact with the bearing would be bad.

Manitunc, Rockitman, magnetic bearings are another thing that I've done experimentation on. In my experience, using the magnets to unload most of the platter weight from the bearing, but leaving some mechanical contact intact sounded the best (a kilo or less, probably even a half-kilo would suffice).

IME, the sonic benefits of keeping a mechanical path to drain away vibrations trump the lower noise levels of a floating bearing. OTOH, if the finish and lubrication of the bearing points is such that significant noise and vibration are generated as a result of the mechanical contact, you may arrive at different conclusions.

Some of the La Platine Verdier turntables allowed the user to adjust the amount of magnetic levitation, and use the configuration that sounded best to him.

cheers, jonathan