SP10 Mk II vs Mk III

Silverprint, I have not done the listening tests necessary to have a valid opinion myself, but the prevailing opinion is that some coupling between tonearm base and bearing/motor is preferable. IOW, those designs you may see with the tonearm mounted separately from the bearing/motor/platter or deliberately decoupled from it seem to get criticized by those who have heard it both ways. What Ralph is saying, I think, is a little more extreme in terms of advocating a specific rigid physical coupling between bearing and tonearm. I actually cannot imagine how to do that with an SP10 or most DDs, because the bearing is of necessity surrounded by the motor assembly. Ralph, please correct me if I'm misrepresenting your view.

Lew, you got it right. Here is the issue- somehow, you need the arm to transduce what is on the LP. In order to do that, there must be no play between the surface of the platter and the cantilever of the cartridge.

To that effect, the arm must have absolutely no slop in its bearings, no resonance in the arm tube. **Any** motion that is not caused by the LP will be interpreted as a sound if these conditions are not met. Thus, to further this, the base of the arm must be rigidly coupled to the surface of the platter. It does this through the bearing, and we are just hoping that whatever bearing we have is good enough. As far as the plinth is concerned, it has to couple the base of the arm to the bearing as rigidly as possible, while at the same time being completely dead. My work with our model 208 proved this to be a very audible aspect!

FWIW, anyone familiar with motorcycle or automotive issues will recognize this mechanical principle as it is the same one that requires that there be no mechanical play or flex between the steering and the wheel on the road, otherwise the vehicle will handle in a dangerous manner.

The plinth of the stock MkII does not take this into account- the arm is mounted on a completely different material. The plinth and the arm base thus have two different resonant signatures; any difference will manifest as a coloration.

Now, we might have the issue where the plinth and arm base are made from a single part, but with vibration the base of the arm is out of phase with the bearing mount; this is why I say ""as rigidly as possible**. As we all know, with LP reproduction we are always talking about microscopic movement and this is an area that the Technics engineers did not, at the time, have sorted. So it is my opinion that in order to get the best performance out of the 'table, that a custom plinth built to accommodate the needs of the Technics would be a very cool thing to build. It would be heavy, but cool.

The Kaneta plinth addresses this issue but taking the motor out of the chassis and place it in the same wood block where the tonearm is mounted.

http://de.geocities.com/bc1a69/kaneta_eng.html

Hiho, Have you ever actually seen the Kaneta modifications applied to an SP10, other than the one in those photos? That URL is frequently cited, but there is no hint anywhere else on the internet that I can find to indicate that help (i.e., kits or assembled PS units) in obtaining the Kaneta outboard supply or the custom plinth are really available. I would be interested to read your response or that of anyone else who has been up close to a Kaneta-modded SP10. The schematic is posted, but it looks quite formidable as a DIY project. (I am quite at home reading schematics and building tube gear but have limited experience with ss devices, particularly ICs.)

Albert,
You raised the issue of the tube power supply - I think it would be not be a wise move, as low voltage - high current power supplies and tubes do not combine.
Using a battery super power supply could be very interesting, but however one should be aware of an interesting feature of this power supply: if by any reason the +5V power supply fails, the +32.5V shuts down immediately, protecting the motor coils.