Stylus Drag

I had used my little strobodisc for years on my turntable. When I used the 3150Hz tone and the iPad app, I found that my speed was low by a few Hz. I didn't hear it as a pitch change, but as a rhythm and pace improvement. I'm hearing all of my records as new just from getting the speed dialed in correctly. That was a learning experience; don't rely on the little stobodiscs. I hear a pitch variation only when playing a pure sinewave. The record runout causes a small but noticable warbling in the pure tone. Improving record runout (filed the hole out and centered the record on the platter) directly reduced the pitch variation.

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.