New TT ideas please

Thom,

You mentioned that your listening group found that "too much" torque in the motor-platter coupling made the sound harsh. Chris's group has reported similar findings.

In our torque experiments (8 or 10 different drive belts, of which the familiar holographic mylar provided the maximum) we heard the same thing. The torque-ier the belt, the more the sound had a tendency to go "harsh".

However, our crazed habit of adjusting and recording SRA/VTA settings for each LP quickly led us to an important discovery. The problem is not "too much" torque. The problem is that different amounts of torque require different arm height settings. Get SRA/VTA right and there's no such thing as too much torque, at least up to the limits of our experiments to date. We'll test this further when Chris's rim drive motor arrives.

We have produced this result consistently and repeatably across many hundreds of LP's, with multiple drive belts. If you checked the notes on our oldest, most-played records, you'd observe a series of arm height settings. They're coded for the different belts we've advanced through. IN EVERY CASE, a change from one belt to any other belt required an identical change in arm height. If I pull out a record today that hasn't been played in a year or two, and so was last played with a less torquey belt, I can reliably calculate and dial in a new arm height based the old one, because there's a constant differential between each belt and the next.

The torque-ier the belt, the lower the arm must go, and by the same amount. We all know that lowering the arm reduces "harshness". This has worked consistently, with every belt, on every record.

We haven't yet heard too much torque and I'm not sure such a thing is possible. The exception would be if higher torque came with higher cogging, as Chris mentioned, but that wouldn't create sonic harshness. It would create waveform slewing and rebound, quite another thing to our ears.

Any thoughts?
Doug

The TT will be on a rack for the time being, but I will work diligently at isolation, be it on the rack, or on a dedicated shelf.

Anyone have an opinion on Acoustic Solid turntables? The One-to-One catches my eye. What little I can find is positive. Any thought here or via e-mail would be appreciated.

Intuitively, I have always thought that every technology has it's place, even within a given design. I have always had a hard time trusting a designer who espouses a one size fits all approach. It seems to me that implimenting layering of harder/lower mass to softer/higher mass plates with increasingly compliant interfaces as you get further from the plinth would be the way to go. This would allow evacuation of internal resonances to be optimized closer to the plinth, and disipation of them, and isolation from external resonances, further from the plinth. Somewhere, probably further from the plinth, the external motor would be coupled, but not so far as to inroduce too much compliancy between the motor and the platter.

Any thoughts on how best to minimize motor resonances in an external motor assembly? Is it better to decouple the motor from its housing with compliant material or to ridgedly couple the motor to the mass of the housing and isolating further downstream?

Thom?

Doug,

How is it possible that VTA is affected by belt torque? It would seem that truly proper VTA, as opposed to tonally judged VTA, would be a separate issue. It sounds like you're using a tone control to cover a problem.

Piedpiper,

Great question, which I've asked myself many times. Wish I had a good answer. I was hoping someone would come up with one!

Geoff Husband's theory is one possiblility. He believes tiny VTA/SRA changes are audible due to specific resonance frequency points in the arm/cartridge system. As torque changes it's likely those behaviors would change, requiring adjustment to re-minimize certain resonances. This doesn't really explain everything we hear, but neither does any other theory.

Regarding tonal balance, our reference cartridge does not change tonal balance with changes in arm height. Any ZYX UNIverse owner will tell you that its bass/treble balance do not change with VTA/SRA. Some lower resolution cartridges (like my Shelter 901 for example) do that. I could have used arm height as a tone control with that cartridge if I'd wanted to, though I never did. With a UNIverse it's not even possible .

With a good cartridge what changes with VTA/SRA, in Frank Schroeder's words, is the temporal integraton of fundamentals vs. harmonics. Paul calls it "temporal smearing" (or preferably the lack thereof).

When arm height is just right, each tonal component of a complex note occurs at just the right time relative to the other components. Temporal smearing is reduced and the note sounds integrated. If arm height is off, the fundamental occurs too early or too late relative to the harmonics, making the note sound either fuzzy (HF's too early) or dull (too late). In addition, peak amplitudes are reduced and waveforms are unnaturally extended in time, making each note sound slower and more rounded. This effect is most audible with LF notes.

Whatever we're doing with arm height, it has nothing to do with tone controls. Our ideal setting for an LP reveals more of the music, not less.

FWIW, the magnitude of height changes from one belt to another is not large. From the weakest belt we kept records for (1 mil mylar) to the strongest (2.2 mil mylar), the differential is 32/100ths of a turn on the TriPlanar's dial. That's an arm height change of just .0224". What's notable is the absolute repeatability in both direction and distance. I can't explain it, but I can hear it and repeat it.

Thanks Doug, for the clarification. I always thought of correct VTA in terms of focus, which is a simple way of dsaying what you describe, relating to the perfect mating of the sylus to the groove, which, at least with the fancier stylus designs, should be quite specific and seemingly independent of any other non-cartridge-alignment issue such as VTF and azimuth.

World without end...