why servo sucks....
In order to pick up sound accurately from the analog disc, the rotation of the platter must be rotated at a constant speed without any “fluctuation”. In general, accurate rotation is obtained by servo control by negative feedback, but at the micro level, if it rotates or becomes faster, it detects it and slows it, and repeats the operation to make it faster if it gets slower. Although this level and cycle are determined by the gain of the control system and the loop speed, the period of the speed control of the platter which is the mechanical system surely comes into the audio band. In general, accurate rotation is obtained by servo control by negative feedback, but at the micro level, if it rotates or becomes faster, it detects it and slows it, and repeats the operation to make it faster if it gets slower. If you try to measure a period with a small level, you can not measure the instantaneous state, so you measure the average value. Therefore, fine vibration generated by servo control can not be measured by the measuring instrument, it depends on the human ear.
the above is my own translation from Jinglish some info that was on the CS Port website 4 years ago. later they removed it. while i'm not claiming that this issue is that simple. or that non servo is the only way to go (two of my three tt's successfully use some sort of speed regulation). but there is some value to keeping in mind the ill effect of servos. and interpretation of our best measurement processes. which is a debatable subject. the alternative of non servo has merit.
musical flow and liquidity are very very valuable commodities in the musical enjoyment equation.
Tim previously rightly chastised me for posting this without attribution.