@slaw- The PBN tach is a bit of a misnomer. The tach counts pulses from a high speed clock (18.518kHz) so it will produce a reading of 33.333 when it takes 1.8S for one platter revolution. However, it is counting the period of rotation, not RPM, so as the platter slows down, the reading will increase and if it speeds up, the reading decreases. The only time the reading is correct is at exactly 1.8S/rev. There is a separate clock for 45 RPM, so the tach must be switched between 33/45. If you can live with those limitations, it is a fairly clever design.
The RR does not need to be turned on or off; the tach comes alive automatically when the platter starts spinning and goes to sleep when there is no activity for 5 minutes. It also has an accumulated playing time counter that can be used to track stylus wear and can be reset when the cart/stylus is replaced.
The RR does not need to be turned on or off; the tach comes alive automatically when the platter starts spinning and goes to sleep when there is no activity for 5 minutes. It also has an accumulated playing time counter that can be used to track stylus wear and can be reset when the cart/stylus is replaced.