Apocalypse Now?—Technics sp10 problem s

Banquo, two suggestions.

One of the best turntable experts in the US is not far away - Brooks Berdan (I think in Monrovia). I would call him Monday morning and ask for his recommendation.

If that fails send me a PM for a suggestion in San Diego.

Good luck.

Too bad there remains so many questions about plinths for Technics and other quality DD tables.

On one hand we have Albert Porter who found sonic delight with ever more massive plinths for his series of SP-10 tables. And the fellow who restored and built new plinths for mikel favors high mass designs. Jweiss has experimented with SP-10 plinths for a few years and his current preference (in slate) weighs about 200 pounds I believe. And if you look at the plinths designed by Technics engineers for their own tables, they increased the mass of each succeeding model for the first three, with the fourth only slightly less than the third.

On the other hand we have Raul, the leader of the pack for plinth less set ups. Apparently Raul began with a massive stone (marble? If so, I agree with Lew that was a poor choice because of the higher resonant frequency -- it rings folks!) plinth, then changed to a single sheet of wood just large enough to support his tone arm, while the motor unit was supported by AT feet. Most recently he eliminated the wood mount and now has his arm freestanding of the SP-10 motor unit. A few others also report pleasing results with plinth less set ups.

Now among those who favor massive plinths, there seems to be one point of agreement. Using only MDF gives poor results. That material may work for idler designs but not for DD, at least the SP-10 series. And I think that points up the importance of the resonance characteristics of the material(s) chosen. Some have tried Corian plinths and I've read criticisms of that material as well. The MDF is slightly dull sounding and damps dynamics while Corian is usually bright with an upper frequency emphasis.

My own experience is very limited. When I got an SP-10 I mounted it on a single sheet of particle board (no one recommends that), simply to provide a platform to mount a tone arm. I will say it sounds very good. But building a better plinth has been long delayed due to finding someone with the tools to help in construction and multiple design changes for what I want.

At this point I find myself in full agreement with Lew. First, I wish someone could report on a comparison of an appropriate massive plinth directly against a plinth less set up. And second, given the critical importance of proper alignment of the stylus tip relative to the record groove, I cannot understand why someone would mount their arm independently from their table, thus giving up the mechanical integrity that a coupled mounting provides.

You don't need to live in NYC. The earth seems to shake easily here in California. ;^)

Banquo, you must accept that every material is subject to vibration, it is just a question of the resonant frequency for each one. I'm not a physicist so admit I am not the best person to answer your question. But my understanding is the higher the density of a material (in general) the lower the resonance. This is why some favor high density in plinths -- to lower the resonance point below the critical 8-12 Hz range. (Which could explain why some prefer plinth less designs, if the lack of low frequency damping and a "brighter" sound better suits their systems.)

I believe this translates to tone arm mounting as well. With a secure mechanical coupling between arm and spindle/platter, material frequency differences (example aluminum and brass or acrylic) may be damped. If each stands alone, they do not damp one another, they can move independently. A further point; many do not realize the potential for urban living environmental activity. I live by a busy street. My turntable is mounted on a wall shelf for isolation. But I can put a stethoscope on the braced plywood shelf and hear traffic going by. If you have an amplifier on the same shelf as your turntable you could experience the same thing. In that environment I would not want my tonearm to be subject to micro-vibrations picked up and translated by a base that was not mechanically damped (attached) to the spindle/platter. Again, consider the extremely small movements of the stylus tip to generate signal.

I think your question on isolating the arm from table motor vibrations has two answers. A decent design will minimize motor vibrations to begin with. But if the motor is noisy, there could be an energy path from the motor, down through the shelf, then up through the freestanding arm. By the time the energy reaches the arm and then stylus, the various materials it traveled through will change its frequency, thus it will vibrate differently than the platter and record. When the arm/cartridge and spindle/platter are mechanically coupled, I believe they should at least vibrate in unison, thus minimizing the impact on the stylus in the groove.

I hope this makes some sense and perhaps another person with more technical knowledge can correct or fill in these points.