VPI Analogue Drive System

Thank you for your responses.  Using the Platterspeed Feickert phone app I know my unit runs a little fast, about 33.5 rpm.  It seems fairly consistent.  It seems to me the Sutherland unit will tell me the same, but how does it slow it down to 33.3 or maybe I would want 33.2 for some recordings that sound too bright?

Keeping the speed at 33.3 is an important function of a speed controller, but it is not the most important thing. Maintaining that speed without micro-speed changes is even ore important and is heard in better, smoother, sound. I can vouch for the ability of the SDS and the Eagle to achieve these goals--and the Eagle (or Falcon)/RR combo is a particularly elegant and simple way to do both.

The VPI ADS can do it, but it is a machine that has been plagued by problems traceable IMO to a less than the best design and the use of very cheap parts. Do you watch "Shark Tank?" Do you know what margins are? I, personally, would not buy one of these things.

At the same time Bill Carlin (Phoenix) has published DIY material for people to make their own speed controllers and it looks like some people may be getting together to turn these out--either as kits or built. If I had to decide now, I would get something I could sell easily (like an old SDS or VPI PLC) and wait to see what happens.

For a tech view of all this have a look at http://turntablepsu.com/vpi.html Though unsigned, it’s probably written by Bill Carlin; nobody knows as much as he does about this stuff.

The Southerland device referred to above, by the way, is NOT a speed controller. It’s just a very expensive strobe.

melm is correct about the Sutherland.  It's a record weight with a strobe built into it.  The only commercially available add-on device that can really "control" the speed of a belt- or idler-drive turntable is/was the Phoenix Engineering Falcon or Eagle power supply combined with the RoadRunner tachometer.  When the RR is attached to the Falcon or Eagle, speed is held as close to constant as the workings of the turntable permit, to the speed 33.333 rpm, because the RR gives constant feedback to the Eagle or Falcon based on real time data streaming from the platter.  Sadly, PE is out of business, but Bill Carlin and some others on DIY Audio are making and selling parts that enable the DIY approach, and for much less money.  The SDS, the Walker Audio Precision Motor Controller, and many other similar devices allow you to set the speed precisely, but they cannot correct for variations in line voltage or current or stylus drag or bearing friction, all of which might cause at least momentary loss of speed stability, once you start listening to music.

lewm

... The SDS, the Walker Audio Precision Motor Controller, and many other similar devices allow you to set the speed precisely, but they cannot correct for variations in line voltage or current or stylus drag or bearing friction ...

This is not really accurate. The devices you describe work with AC synchronous motors; line voltage and current have no affect on speed, which is governed by the AC line frequency. (That's the "synchronous" in "synchronous motor.") AC line frequency is very tightly controlled by electric utilities, because deviations in frequency can unbalance power distribution systems. It's unlike voltage, which can vary widely without causing disruption in power delivery.

As for bearing friction and stylus drag - these are really only factors with lightweight turntables and platters.  Once the platter has sufficient mass, these variables have little to no influence on platter speed.