Direct drive vs belt vs rim vs idler arm

Hi Dover,

I stand corrected, I think. This is where I got tripped up on your post with the word "and" being key. "I said it is an assumption and that if the belt doesn't stretch then there is no creep."

More from Mark Kelly:

"Some form of tensioner (always on the "non-drive" side) will eliminate slip, but it won't touch creep.
Creep is necessary for a belt drive to work. The mechanism of creep is how the belt transmits force from the pulley to the platter, so no creep = no rotation."

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Mosin - no worries. The silk thread I use only seems to slip fractionally on start up, but the 20kg platter can be up to speed in less than 1 rotation, depending on how I tension it, which I think is pretty good considering the pulley is only about 10mm versus the 20kg platter. This suggests the silk has very good grip. With the high mass platter it does drive the motor pulley as well. If I turn the motor off, the platter/thread will drive the motor for a while. The designers original intent was that the silk should be "chalked", I presume for a controlled slip, but I prefer direct. The silk lasts a long time as in can go for a year or two. The only breakage I've had in 20yrs is when I've moved the deck and once when I went on holiday for 6 weeks and left the TT running ( I think high humidity weakened the silk fibre ).
Timeline speed checked on playing records inside/out etc and it's rock solid. These things all come down to the quality of the implementation, whatever direction is chosen.

"These things all come down to the quality of the implementation, whatever direction is chosen."

Exactly. :)

First, belt drive tt's in general have high mass platters.

Tony, some belt drive decks have high mass platters, but MOST? Some certainly do, but I would venture to say that most belt drive decks on the market, both new and used, do not have or were not designed with platters that I would characterize as high mass platter.

But I guess it depends on what you consider to be "high mass".

I'd say that high mass would be something like 100 times greater than the mass of the record. That would be about 15 kg.
This discussion got me in the mood to check my platter speed again. After playing several records the tt was warmed up and I know from measurements before that warmup is critical. I had a small bit of drift (about 0.5Hz out of 3150 Hz) after setting the speed several months ago. I dialed speed back in and had some good results: -0.01%/+0.02% Wow&Flutter and the speed plot over time shows a sine wave with a 5 second period. I believe the +/- speed variation over 5 seconds is the control system holding speed about the setpoint (At any rate I feel these values are well below audible detection and are an order of magnitude better than the records themselves.) This app is a very good objective measurement tool, I think, for dialing in speed and checking to see if your tt is operating within the manufacturer's specifications. No more, no less.