Knife Edge Bearing - Pros & Cons?

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syzygy
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Re: Knife Edge Bearing - Pros & Cons?

Post by syzygy » 15 Jun 2018 12:30

I am awaiting reviews of the new Jelco arms.

bimasta123
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Re: Knife Edge Bearing - Pros & Cons?

Post by bimasta123 » 18 Jun 2018 22:15

@watchnerd — You ask:

"If given the choice between:

a) Keeping my current Jelco SA-750D gimbal tonearm, with the ability to tune damping with its oil reservoir

or

b) A new Jelco SA-850S, with theoretically superior knife edge, but no ability to tune

which would you pick and why?"


Judging from photos, there are several other differences between the two models; all will be factors in sound quality. It would be a mistake to make a decision based solely on the type of bearing. Damping may be more significant, but I've had arms both with and without damping, and to my ears it makes little difference. I had a Jelco with damping (then it was branded Audioquest) — I used it at first, then stopped.

The only arm-damping that seemed to make a big difference was the Townshend, where the damping is applied right at the headshell — but along with the big difference came a big hassle.

watchnerd
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Re: Knife Edge Bearing - Pros & Cons?

Post by watchnerd » 19 Jun 2018 06:32

bimasta123 wrote:@watchnerd — You ask:

"If given the choice between:

a) Keeping my current Jelco SA-750D gimbal tonearm, with the ability to tune damping with its oil reservoir

or

b) A new Jelco SA-850S, with theoretically superior knife edge, but no ability to tune

which would you pick and why?"


Judging from photos, there are several other differences between the two models; all will be factors in sound quality. It would be a mistake to make a decision based solely on the type of bearing. Damping may be more significant, but I've had arms both with and without damping, and to my ears it makes little difference. I had a Jelco with damping (then it was branded Audioquest) — I used it at first, then stopped.

The only arm-damping that seemed to make a big difference was the Townshend, where the damping is applied right at the headshell — but along with the big difference came a big hassle.
I understand your logic, but absent any other information (or reviews, or having a sample on hand to compare), I really don't have anything else other than bearing differences to go on:

arm tube seems the same, from what I can tell

anti-skating seems the same

mounting collar seems pretty close to the same (although moot in my case, given I use VTA on the fly)

headshell interface seems the same

this seems to leave the bearing differences and with/without oil damping as the obvious differences

noromance
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Re: Knife Edge Bearing - Pros & Cons?

Post by noromance » 08 Dec 2018 15:14

To answer the guy asking for input on whether the Jelco 850 was worth upgrading to from the 750. Absolutely. The 850 is in a different class.

watchnerd
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Re: Knife Edge Bearing - Pros & Cons?

Post by watchnerd » 08 Dec 2018 15:22

noromance wrote:
08 Dec 2018 15:14
To answer the guy asking for input on whether the Jelco 850 was worth upgrading to from the 750. Absolutely. The 850 is in a different class.
What cartridge are you using?

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Re: Knife Edge Bearing - Pros & Cons?

Post by noromance » 08 Dec 2018 16:40

Decca Super Gold with Paratrace stylus.
Also tested it with Ortofon MC3 Turbo HOMC.
See my notes in Audiogon.

watchnerd
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Re: Knife Edge Bearing - Pros & Cons?

Post by watchnerd » 08 Dec 2018 16:47

noromance wrote:
08 Dec 2018 16:40
Decca Super Gold with Paratrace stylus.
Also tested it with Ortofon MC3 Turbo HOMC.
See my notes in Audiogon.
Link?

eliash
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Re: Knife Edge Bearing - Pros & Cons?

Post by eliash » 09 Dec 2018 14:43

watchnerd wrote:
04 Jun 2018 04:14
The new TK series of Jelco tonearms (TK-950, TK-850) use knife-edge bearings, a departure from the ball bearings used in the SA-750 and its replacement, the TS-550.

As an owner of a Jelco SA-750D, I'm curious:

What are the pros & cons of knife edge bearing tonearms?
Ball bearings were reported to have some bearing chatter (in the KHz-range), maybe Jelco wants to avoid it, or found them better suited for MC application.
...Switching from Shure V15 IV (high compliance MM) to Benz Micro ACE S (lower compliance MC) on a Thorens TP50 tonearm (horizontal ball and vertical conical pivot bearings) subjectively seems to stress this tonearm a lot more...
Ref.:
http://korfaudio.com/blog12 ...and following
http://korfaudio.com/blog26

watchnerd
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Re: Knife Edge Bearing - Pros & Cons?

Post by watchnerd » 09 Dec 2018 15:10

eliash wrote:
09 Dec 2018 14:43
watchnerd wrote:
04 Jun 2018 04:14
The new TK series of Jelco tonearms (TK-950, TK-850) use knife-edge bearings, a departure from the ball bearings used in the SA-750 and its replacement, the TS-550.

As an owner of a Jelco SA-750D, I'm curious:

What are the pros & cons of knife edge bearing tonearms?
Ball bearings were reported to have some bearing chatter (in the KHz-range), maybe Jelco wants to avoid it, or found them better suited for MC application.
...Switching from Shure V15 IV (high compliance MM) to Benz Micro ACE S (lower compliance MC) on a Thorens TP50 tonearm (horizontal ball and vertical conical pivot bearings) subjectively seems to stress this tonearm a lot more...
Ref.:
http://korfaudio.com/blog12 ...and following
http://korfaudio.com/blog26
That's about an SAEC arm, not a Jelco.

eliash
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Re: Knife Edge Bearing - Pros & Cons?

Post by eliash » 09 Dec 2018 16:46

watchnerd wrote:
04 Jun 2018 04:14

That's about an SAEC arm, not a Jelco.

Sorry, just meant as an example for the ball bearing noise (in the diagrams)...