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Original Message

RE: Second that on the headshells!

Posted by flood2 on January 3, 2017 at 16:17:20:

"Please note that with speed changes so does pitch change"

Exactly!
For the benefit of anyone not already familiar with the term, in a motor, the cog (or detent) is defined as:
the point at which the center of the magnets perfectly line up with the ideal magnetic path through the poles.
The effect this has on the motor rotation depends on the pole construction.
With this in mind, it should therefore be clear that cogging isn't restricted to DD turntables....it applies to ANY motor. Therefore a belt driven turntable is vulnerable to cogging. The belt and the pulley ratio are what ameliorate the effect. However, the torque transmission changes with the belt tension which will be influenced by motor cogging. So motor cogging would manifest itself in higher wow and flutter figures.
Wow and flutter figures would therefore be the best measure to determine which was the turntable likely to give the best pitch stability.
When it comes absolute pitch stability, the SL1200 is certainly "up there" with the better decks. Absolute pitch level depends on how well the centre position of the pitch control pot was set initially (and can easily be reset - which I have done with mine), but the motor control does an excellent job.

Unless there is a fault in the motor drive somewhere, rest assured there is no cogging with the 1200! It hasn't been "solved" with the new model - it didn't exist before, but due to the popular misconception that all DD decks suffers from cogging, Technics would naturally draw attention to that as an "improvement" to encourage new sales. Certainly the wow and flutter figures given in the HFNRR review I saw show a small improvement over the original, but the original was already considerably better than the majority of belt driven decks that didn't have proper motor control.
Anyone in the press or elsewhere making claims of cogging with the 1200 is basing it on personal bias and not the facts. The HFNRR of the SL-150 I mentioned already showed that even without a quartz-lock based control system, the simpler drive control still didn't exhibit cogging.

However, if you ARE hearing pitch changes then I would point the finger first at an eccentric disc OR if the disc is a remaster or original analogue recording, then the pitch shift existed in either the recording itself or the playback of said recording during cutting...or even inherent to the lathe itself!

As I have mentioned before, there is zero evidence of cogging related artefacts in the spectral analysis of my recordings.


For me, the priority is consistency in performance and pitch stability. Any deck that is sensitive to temperature changes in the belt material etc is hopeless from the get go and the fact that the materials used are sensitive to the environment of use should already indicate that you are not going to be getting consistency over time.

Getting back to your experiment, remember that the DL103 is a lowish compliance cartridge and that the effective mass of the Technics arm (12g)is higher than the SM309 (9.5g) so would in principle be a slightly better match. The LF arm resonance value modulates the recovered signal so depending on how well damped the resonance is, you are going to get differing levels of colouration. The resonance of the 103 with the SME309 will be higher so the sidebands will be wider spaced around the central frequency/frequencies of the recovered signal. This will affect your perception and therefore is telling you more about the arm/cartridge match than the motor drive principle on the deck.