Quartz lock in a belt drive?

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lenjack
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Quartz lock in a belt drive?

Post by lenjack » 21 Jan 2019 16:57

I'm curious. Has there ever been, or could there be, a quartz locked belt drive table? :?: #-o :idea:

Japi Roelofs
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Re: Quartz lock in a belt drive?

Post by Japi Roelofs » 21 Jan 2019 17:25

Yes. Dual CS-5000, and Philips AF-887 / 829 II / 977 come to mind...

lenjack
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Re: Quartz lock in a belt drive?

Post by lenjack » 21 Jan 2019 17:28

Interesting. I would have thought not. :o

Smoke Screen
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Re: Quartz lock in a belt drive?

Post by Smoke Screen » 21 Jan 2019 23:15

lenjack wrote:
21 Jan 2019 17:28
Interesting. I would have thought not. :o
Well,at the time back then fg-servoed belt drives you could find even in the
entry level class,like for example Pioneer PL-516,but q-locked servos for belt drives
were noticable more rare and mostly upper class models like the mentioned ones
and the Harman Kardon T-60,T-65 models.
Lately the industry is discovering the fg-servo for belt drives again,like in the new
Fluance models,although w&f still doesnt improve much against well designed belt
drives with ac-sync motors. My guess is that still very cheap dc-motors are used which
limits the benefit of a servo.

lenjack
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Re: Quartz lock in a belt drive?

Post by lenjack » 21 Jan 2019 23:31

I did try 2 of the earlier Fluance's, but couldn't tolerate the speed quirks. Settled on a well serviced Craig's List SL-d3, and couldn't be happier.

fg?

analogaudio
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Re: Quartz lock in a belt drive?

Post by analogaudio » 22 Jan 2019 01:37

Quartz-lock as applied to the popular direct drive platter systems includes a method of returning to the motor drive circuit information about the actual motion of the platter in real time and which is used to make corrections to the platter drive that improve speed stability. This might be called a closed-loop system, there is feedback (derived via a sensor of some sort) from the output (platter rotation) to the input (motor control speed reference).
It may be that this feedback also exists in belt-drive variations of the principal. However it may also be that there is no feedback from the platter and that the system is open-loop. This would be the case with a "frequency generator servo" type of belt drive which uses a sensor within the motor to regulate the motor speed, however there may be no sensor for the platter rotation, and therefore no feedback for speed stability improvement, which remains that delivered by the performance of the motor pulley plus belt plus platter drive rim, which can be expected to introduce errors not present in the performance of the motor itself.

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Re: Quartz lock in a belt drive?

Post by Smoke Screen » 22 Jan 2019 18:07

lenjack wrote:
21 Jan 2019 23:31
I did try 2 of the earlier Fluance's, but couldn't tolerate the speed quirks. Settled on a well serviced Craig's List SL-d3, and couldn't be happier.

fg?
Right.
Fg means frequency generator.
On the Fluance`s: That seems to be a QA problem. Many are satiesfied with them but some have issues.
BTW: My first turntable back in the early eighties was a servo controlled belt drive from Pioneer. It had
a open loop system,still less than 0,05% w&f - but the motor (PXE-054) was of decent quality.

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