Servo is from Latin for slave.

Posted by Mark Kelly (M) on July 5, 2005 at 06:33:43

In Reply to: Please explain servo vs. quartz locked posted by rogercanada2004@yahoo.ca on July 5, 2005 at 05:20:35:

A servo is any mechanism which is the slave to a master signal. I believe the term was coined in French in the 19th century to describe a motorised rudder mechanism for ships (interestingly cybernetics comes from the Greek for a helmsman, the non-motorised predecessor).

In electronics a servo circuit is one where feedback is used to return something to a specified position or rate, eg the low frequency feedback amplifier which corrects DC offset in a solid state amp is called a servo.

In the case of direct drive turntables it refers to active speed correction. The earliest way to do this was simply to measure the speed in the form of a signal derived from the platter movement, compare it to the correct speed in the form of the output from a high stability oscillator and then speed up or slow down the motor as required. Oscillators are usually based on quartz crystals (just like clocks).

An elaboration of this is to mix the speed signal and the oscillator signal using a phase sensitive detector and feed the output of the detector back into the servo loop which then acts to ensure that the phase difference between them stays constant. This is called a phase locked loop.

I have read that the Mk 2 Technics are PLL and the earlier ones are not but I can't swear to it.

To every human problem there is a solution which is simple, neat and wrong - H.L Mencken

Mark Kelly

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Follow Ups Full Thread

Topic - Please explain servo vs. quartz locked - rogercanada2004@yahoo.ca 05:20:35 07/05/05 (13)

My Technics DD experience - daviddeep 20:48:36 07/05/05 (2)

Regarding the SL1500 - bkearns 03:50:50 07/06/05 (1)

Forgive my technological ignorance - daviddeep 07:18:25 07/06/05 (0)

First: Separate the marketing from the technology.... - doodlebug 10:29:57 07/05/05 (0)

Re: Please explain servo vs. quartz locked - maabx 06:59:50 07/05/05 (0)

Re: Please explain servo vs. quartz locked - maabx 06:49:52 07/05/05 (0)

Servo is from Latin for slave. - Mark Kelly 06:33:43 07/05/05 (5)

Re: Servo is from Latin for slave. - Muzikmike 08:21:45 07/05/05 (4)

Re: Servo is from Latin for slave. - melomane 17:15:53 07/05/05 (0)

Whatever yer smokin', got any more??? /nt\ - HenryH 08:40:01 07/05/05 (2)

As a matter of fact... - Muzikmike 09:23:59 07/05/05 (1)

Luv that hickory smoked ham. . . yum . . . yum. /nt\ - HenryH 10:48:54 07/05/05 (0)

My meager understanding is as follows... - EdAInWestOC 05:41:24 07/05/05 (0)

Follow Ups

Servo is from Latin for slave. - Mark Kelly 06:33:43 07/05/05 (5)

Re: Servo is from Latin for slave. - Muzikmike 08:21:45 07/05/05 (4)

Re: Servo is from Latin for slave. - melomane 17:15:53 07/05/05 (0)

Whatever yer smokin', got any more??? /nt\ - HenryH 08:40:01 07/05/05 (2)

As a matter of fact... - Muzikmike 09:23:59 07/05/05 (1)

Luv that hickory smoked ham. . . yum . . . yum. /nt\ - HenryH 10:48:54 07/05/05 (0)

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