Stylus Drag

It occurred to me re-reading some of these threads that no one has mentioned some turntables have closed loop speed control systems while the rest are open loop. That means if you put your finger on the rim of the platter ever so slightly just to add some drag and you hear/see the speed drop and stay low, then your tt is an open loop speed control. A closed loop system has a speed sensor and the control system will add/subtract torque as needed to maintain the set speed. If you touch the rim of a closed loop table you might see/hear the speed change momentarily but then correct itself. My turntable is open loop. I have a speed dial to adjust the speed and I adjusted it while playing a record, but any changes in load on an open loop turntable will affect the speed of the platter. If the friction varies from one record to another, then our open loop tt's will have slight variations in speed. Probably too small to notice, but it is there. I don't know which tables are closed loop design vs. open loop, but I think just about all DD turntables are closed loop. The timeline device probably seperates out the closed loop tt's from the open loop systems. That's because the closed loop tt's are going to maintain a constant speed by adjusting torque as the needle is dropped onto the record and as the friction/drag varies while playing the record. Again, I don't necessarily hear it as a pitch change but more as rhythm and pace.

Tony, Thanks for your very informative comments on this thread. I was not aware of difference between open and closed loop systems. According to the manual, my SME turntable uses a closed loop speed control system. Perhaps it is one of the few belt-drive tables that does. I've found the speed is constant and stable, but I've only tested with the KAB strobe. I plan to use a digital tachometer and perhaps also try a test tone.

Probably my own "dictionary". :-) I think of "stylus drag" as the potential for minute changes due to congested passages, rather than just simply friction, which is more noticeable on sustained notes. The kind of changes those of use who use mylar belts hear between a belt with the metal still on, and one that has had it removed with etching solution. Same cartridge and feedback controller, but there is more clarity through congested passes due to improved drive, contact, etc.

Peterayer, the SME table embodies to me, everything a turntable should be- massive platter, state of the art speed control, great sound and great looks. If I had the means I'd let SME spin my records. Happy listening.

I assert that small changes in speed caused by stylus drag can be heard. Frogman is heading in the right direction.

I would also agree with Tonywinsc that pace/rythm is another way to gauge the effect of speed stability. In my experience, a table which is less sensitive to speed variation caused by stylus drag during heavily modulated passages tends to preserve both the dynamics and timberal aspects of crecendos and dynamic passages.

I believe it also preseves the detail of micro-dynamics...and i think this is where Atmasphere and Mosin may be referring to.

Andrew