Speed strobe recommendation.

The best feature of the KAB is that the strobe is a 300Hz strobe light, and there are speed-designation numbers on the disc that are very easy to read while in operation. No more mesmerization trying to look at that single bar hopefully holding steady...squinting...

-Richard

There is a caveat here: in the case of a typical, single-phase synchronous AC motor connected to the mains supply (think lower-end Thorens, Rega, VPIs, AR, some Projects, etc) its speed is derived by the incoming mains frequency - 60Hz here in the US. If the mains frequency is say .25Hz low (59.75Hz), then your table will run slightly slow but you'll never know - as the light you are pointing at the strobe disc to derive speed accuracy is also running .25Hz low. Hell, the speed could be wandering all over the place, but with the table and the fluorescent light clocked to the same frequency, you'd never know!

Of course, this doesn't apply to Doug, as his deck uses a DC motor - many other folks use AC motors, but with some type of dedicated external supply (like an SDS, Lingo, SpeedBox etc) which (theoretically) ought to take care of such issues.

Of course if good enough is sufficient, so be it. Have a pleasant holiday season!

-Richard

Doug,

I believe tolerances for mains frequency delivery here in the US is specified at +/-1%, translating to a .6Hz variation. My note above merely specified a .25Hz deviation (which is a lot, but does sometimes occur). I understand the principles behind power generation, but rarely do specs match reality. Every day power grids correct frequency variations due to a wide variety of causes (equipment malfunction, load variances, etc) so that in the end things that depend on an accurate mains frequency (like clocks) are more or less accurate. It is, however, the shorter-term, briefer duration changes that would be affecting something like turntable playback (with an uncorrected AC synchronous motor). Subtle, but certainly there, and possibly enough to induce a false reading using a fluorescent lamp and a strobe disc (on any type of motor). Plug an accurate (to the hundredth of a Hz) frequency counter into a power line - you might be surprised.

http://leapsecond.com/pages/mains/

-Richard