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Turntable speed stabilty
Turntable speed stabilty
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Old 2nd February 2018, 08:36 AM   #1001
gpapag is offline gpapag  Greece
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Turntable speed stabilty
The decoupling of the counterweight on Dual arms was not a simple rubber collar.
Also, the elastomer parts were not exposed, so protected from UV. I have services 4-5 of old Duals, the behavior at the subsonic range was very good.

The ST line of B&O tonearms had the horizontal gimbal axis attached to a conical soft rubbery insert (damping at the vertical plane). It was exposed to the light. It degraded with time.
There was also a rubber bushing at the mounting of the arm to the armboard.

George
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File Type: png Dual counterweight.PNG (934.2 KB, 173 views)
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Old 2nd February 2018, 02:31 PM   #1002
Hans Polak is offline Hans Polak  Netherlands
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Quote:
Originally Posted by gpapag View Post
The decoupling of the counterweight on Dual arms was not a simple rubber collar.
Also, the elastomer parts were not exposed, so protected from UV. I have services 4-5 of old Duals, the behavior at the subsonic range was very good.

George
Hi George,

At a first glance it looks quite sophisticated, but as mentioned before, there is not one size that fits all and that's what you see here.
What makes it still look rather good is the fact that the vertical scale is not logarithmic but linear. Not corresponding to the way we perceive sound.

I simulated their findings, and came with comparable results for a counterweight tuned at 6.4Hz.
The results, but now on a logarithmic scale are visible at the image below.
With their Arm/Cart combo's having a very high Fres peak of ca 15 dB, the damping is in no case more than ca. 3 dB.
With a better damped Cart, damping result would be even (far) less.


Hans
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File Type: jpg Damper3.jpg (188.2 KB, 168 views)
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Old 2nd February 2018, 02:54 PM   #1003
super10018 is offline super10018  United States
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Here is another interesting read about turntable speed. Make sure to read the comments from Mat Weisfeld and Ortofan.

Exclusive: One Week With Technics' New SL-1000R Direct Drive Turntable | Analog Planet
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Old 2nd February 2018, 03:10 PM   #1004
Hans Polak is offline Hans Polak  Netherlands
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And just to show the difference, this is how it would have been after fine tuning the spring rate and the damping within the counterweight, which of course is not within the possibilities of the real thing.
Damping has now more than doubled in dB's.
With damping I mean the height of the original peak at Fres versus the highest point in the damped curve.
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Old 2nd February 2018, 03:31 PM   #1005
billshurv is offline billshurv  United Kingdom
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Turntable speed stabilty
Well as ever, Fremer needs a better tool, like the one this thread is/was about.
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Old 2nd February 2018, 06:18 PM   #1006
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by Hans Polak View Post
And just to show the difference,
Job well done as usual Hans !

Quote:
which of course is not within the possibilities of the real thing.
Keep in mind, we are working on paper, they were working on a real product (specs, reliability, longevity) and a need to cover a whole range of cartridge compliance.
For a narrow range of cartridge compliance, the leaf spring and the elastomer damper can be twicked/optimised.

George
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File Type: png Dual counterweight damping.PNG (911.2 KB, 135 views)
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Old 2nd February 2018, 07:04 PM   #1007
gpapag is offline gpapag  Greece
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Do you remember the humble NAD 5120? (actually a Tesla NC470)
https://worldwide.espacenet.com/publ...C=A&popup=true

George
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File Type: png NAD 1.PNG (370.3 KB, 143 views)
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Old 3rd February 2018, 09:41 AM   #1008
Hans Polak is offline Hans Polak  Netherlands
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Originally Posted by gpapag View Post
Do you remember the humble NAD 5120? (actually a Tesla NC470)
https://worldwide.espacenet.com/publ...C=A&popup=true

George
It's hard to believe that 30 years ago you could buy such an ingenious piece of engineering, protected by a patent, even including a turntable for 129,- GBP.

Hans
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Old 3rd February 2018, 12:47 PM   #1009
gpapag is offline gpapag  Greece
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Turntable speed stabilty
Regarding the low price of the NAD (it was 95 to 100 GBP) we can assume it was due to the benign influence of the priorities of Jiri Zanda.
The publishing/promotional establishment didn’t move an eyelid, the crowd wasn’t impressed, so we can safely assume that in the big arena, technological ingenuity is a waste of both time and effort when steered toward solving vinyl playback problems
(“I don’t see a problem”, or “don’t touch it, you’ll destroy that magical sound”)

George
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Old 3rd February 2018, 01:27 PM   #1010
scott wurcer is offline scott wurcer  United States
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technological ingenuity is a waste of both time and effort when steered toward solving vinyl playback problems
(“I don’t see a problem”, or “don’t touch it, you’ll destroy that magical sound”)
Does anyone remember if this is the arm that Martin Colloms (?) measured with an accelerometer and found a 300Hz flexural mode?
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