New Teres Direct Drive Motor Available as Option

Pauly, Your stylus drag experiment is interesting...
Physics dictate that the uneven forces from stylus drag will modulate the platters speed. What can be debated is if the effect is large enough to be audible. Our ears are remarkably sensitive to errors in the time domain. Far more so than would seem logical and far more than most would expect.

Contrary to popular thinking platter mass only changes how stylus drag affects speed but cannot eliminate it. A massive platter will reduce the magnitude of the variation but extends it over a longer period of time. A light platter will conversely allow a larger speed variation but it recovers more rapidly. Most, but not all, prefer the shallower variations from a heavy platter but it is a compromise, not a fix.

The Verus motor does show greater improvement (compared to our belt drive) when coupled with a light platter. But there is no evidence that using a heavy platter with a Verus motor is detrimental. We have used the Verus motor with platters up to 70 pounds and as with our belt drive motors have consistently preferred the heavier platters. What we have found is that with the Verus motor platter mass seems to be less important. For example we recently did some comparisons between a 14 pound solid acrylic platter and a 27 pound lead/acrylic platter. With the Verus motor the difference between the platters was about half of the difference heard with a belt drive Signature motor.

So does the Verus motor with a light platter surpass our heaviest platter with a belt? I have not done that comparison but suspect that the answer would be no. But there is much more to the story than mass. The materials used in our 360 platter (brass and cocobolo) sound a lot better than acrylic.

Chris

Very interesting discussion. I look forward to receiving mine in a month or so :-)!

It's generally accepted that a constant, steady platter speed will produce the most accurate reproduction. Above, Chris stated that a high mass platter will produce speed variances of low magnitude and long duration, and that light platters will produce speed variances of high magnitude and short duration.

A main goal of TT design is steady platter rotation, but could TT designers be barking up the wrong tree? Shouldn't we consider the speed variances of the cutting lathe and try to produce a TT whose platter mass, motor power, and stylus drag combine to approximate the speed variances of the cutting lathe? If the cutting lathe's platter slows down and recovers due to a heavy modulation, it might not sound right when replayed in your living room if your TT's platter also doesn't slow down and recover at the same rate. Is it possible that rock solid speed stability in TTs is actually a bad thing?

Ketchup - Your post is most intriguing, and brings up an interesting point.

Are most lathes direct drive?

Ketchup, One would need to know a lot more about how a cutting lathe works. Perhaps someone among us can enlighten the rest. But if your idea has any validity, then in effect "stylus drag" is a good thing. There seems to be a body of empirical evidence that this is not the case. I would guess that cutting lathes use powerful high torque motors that are securely connected to the lathe, so that heavily modulated passages are treated no differently from those that are less so. But I'm just guessing.