New Teres Direct Drive Motor Available as Option

Jean,

I think I understand your comparison of idler drive to belt drive, but I'm lost in your comparison of idler to Verus rim drive.

I would think the comparison of rim drive to idler drive boils down to the relative compliance of the interface between motor and platter. With rim drive there will be speed instability if the rubber ring around the transmission wheel has excessive compliance. Is idler drive really much better in this regard?

There is also the matter of transmission of motor rumble. But as with your replinthed Lenco, noise problem can sometimes be engineered.

The torque necessary to meet the changing force of stylus drag is far less than what is necessary to lift an 80 lb. plinth. But it is nice to know that a Lenco motor could be used to drive an electric bicycle.

Don't forget there is also the benefit of high platter mass to counteract the negative acceleration. It is the weight of that spinning flywheel that stores energy and helps get the car off the line. Too heavy, the car is slower to build rpms. Too light, and the car doesn't leave as quickly. The whole system should be analyzed, not just the individual parts. Relative to those light-weight cast or stamped metal tables of the earlier idler/rim drive 'tables the Teres platters are 3 or four times the weight. As Swampwalker said, the high torque may be great for getting the platter spinning from stop but once the platter is at speed, how much torque is needed to maintain constant speed? Which is a state of near zero acceleration. The energy stored in a 30 to 40 lbs platter is helping a lot. The connection of the LP to the platter must also be considered. It does no good if the platter is marching along but the LP is slipping on the surface.

"by offering relative immunity to minute changes in platter speed that might other wise result from stylus drag"

I would agree with that. IMO, this is also why the mylar belts are superior to all other belts I've heard. They don't stretch at all. However, they can slip ever so slightly and that is where the door is open for the possibility of rim drive. Obviously, the next step up should be direct drive, and it goes without saying that every drive systems needs to be well implemented.

Stylus drag – real or myth?

Some time ago I did an experiment to determine just what effect stylus drag would have on an LP. I used a DL103 set to 2.5 gram tracking weight and used a regular 120 gram LP on a cheap mat felt mat (I believe off one of my old Regas). I made a small notch in the edge of the record and aligned it to a piece of tape on the platter. Looking up the edge of the tape (akin to looking down the sights of rifle) I could line up the notch in the LP very precisely.

The one side of the record was played (approx 20 min). The record was unclamped.

Now if the average groove speed is about 14.1 inch per second (20 inch per second on the outer grooves, 8.3 on the inner most groove), that means I am looking at about 1410 feet (16920 inches) of groove length.

After playing, the record shifted at the very most, not more than 1/64 of an inch. That means that over a period of 20 minutes and distance of 16920 inches, stylus drag amounted to only 1/64 of an inch of record slippage; or stated differently 9.235e-5 % slippage.

I did not bother to measure/calculate and compare the amount of drag needed to slide the unclamped LP on the felt mat vs. the drag need to overcome the rotational inertia of a 12 pound platter (never mind the 30 plus lbs Teres platters). I simply cannot buy into the idea that the force of the rotational mass of a platter would be less than the force required to make a 120gram LP slip.

I have not heard a Teres as yet, but I did own an idler wheel (TD124). The idler wheel had no more speed stability than any of my AC motored belt drive turntables.

Regards
Paul

Dan_ed,

Somewhere in this thread it's reported that in testing, Verus rim drive produced the greatest improvement in combination with the lightest Teres platter. It would seem that with rim drive (as with idler drive), high platter mass might actually impede speed stability (probably at the point where the motor has insufficient torque to meet the higher rotational force associated a high-mass platter.) But I suppose that high-mass platters are also better at resonance control. So there is likely a trade-off with how light one would want to go without resorting to fancy TT mats and other approaches to resonance control.

Since with rim drive as with idler-drive, speed stability is entirely determined by the motor, it would be interesting to know whether the 1800 RPM motor of the Lenco offers an inherent advantage. I assume that with the Verus, the drive pulley is pressed onto the spindle of a low speed motor. Perhaps the best rim-drive design would be a high-speed motor with multiple wheels and a step-down transmission. This might also improve isolation of motor noise.

Finally, issues of force and compliance surrounding stylus drag can't be too much different than issues regarding VTF. This is handled easily in a TT arm by counterweights & gravity.

Dgarretson,

That is along the lines of the point I was attempting to make. A given motor speed and torque in the rim drive system may have a range of platter weight that works best with that given motor. Then again, it could be testament to how well these heavier platters with mylar belts actually work. ;)

I think the extra gears of a reduction system are going to introduce more noise. IME, gears don't mesh silently and there will still be slop between the teeth. That is why the Lenco rubber-tired idler wheel can work well when everything is in good shape.

"Finally, issues of force and compliance surrounding stylus drag can't be too much different than issues regarding VTF. This is handled easily in a TT arm by counterweights & gravity."

I would agree with you on how easily this is handled except that so many tables/arms don't. Perhaps that attributes to the rising price structure of many 'table/arm lines?