Jelco effective mass

[Artifolk]

Anyone here know what the Effective mass of the Jelco SA -750db is? I can't seem to find a reliable source.

Also am i right in thinking the Headshell mass is 12Gr?

Thanks in advance.

[selfaddict]

I have this info, cannot remember where I got it:

Effective mass 20gr for SA-750D 9"

Effective mass 26gr for SA-750L 12"

Effective mass 18gr for SA-250ST 9"

[Gromit]

I have this info, cannot remember where I got it:

Effective mass 20gr for SA-750D 9"

Effective mass 26gr for SA-750L 12"

Effective mass 18gr for SA-250ST 9"

I see there was an answer from the Head of Sales at Jelco (in Japan I think) to a letter written by someone on VE - he stated it was 20g but didn't say if it was with or without headshell. I'd presume without, seeing as the SA250T is would be very close at its own 18g eff mass (which is fixed shell).

The info does seem somewhat elusive though - been searching for a while myself. :)

[Artifolk]

Thank you. I had Emailed Jelco direct for the answer, if i get a reply i'll post here, just for future reference.

Does seem strange them not showing the Effective mass in their Spec sheet tho. Surely its one of the most important aspects for Cartridge matching.

[Gromit]

Does seem strange them not showing the Effective mass in their Spec sheet tho. Surely its one of the most important aspects for Cartridge matching.

Those were exactly my thoughts too. :scratch:

[AlexM]

Anyone here know what the Effective mass of the Jelco SA -750db is? I can't seem to find a reliable source.

Also am i right in thinking the Headshell mass is 12Gr?

Thanks in advance.

Charles,

The standard headshell is a tiny bit under 12g.

The arm's effective mass is 20g, as shown in this email from Jelco below (posted to Vinyl Engine). I can't imagine that the effective mass is quoted without the headshell - that would be 32g, and most modern medium/low-ish compliance cartridges would be rendered incompatible.

Posted Mon, 01/25/2010 - 20:45 by Alfredo56

I asked the news of the effective mass Jelco arm SA 750-D, the answer:

Dear Bisogno,

Thank you for your inquiry for SA-750D tonearm.
Effective mass is 20gr.
Damping oil is 500cps silicone oil.

Best regards.

Haruo Uchida/sales manager.


Kind regards,
Alex

[matador]

New info (http://audiosensibility.com/blog/accessories/jelco-tonearm-store/jelco-tonearm-faq/) about effective mass:
13273
:scratch:

[Marco]

Hi Andrew,

The answer is that the Jelco SA-750D (the most commonly sold model) has an effective mass of just under 14g, which of course can be tailored (mass decreased or increased) by fitting a lighter or heavier headshell to the tonearm.

Ignore other info in that respect, given earlier on the thread, as it is bogus.

The SA-750D is thus best suited for use with low to medium compliance MC cartridges. The Denon DL-103, for example, is a really good match.

Marco.

[matador]

Hi Marco! Thanks for reply.
I've also contacted with Jelco Ichikawa support and asked them to confirm this information.
They confirmed it:

Thank you for your inquiry for SA-750L(12") effective mass.
Details as follows.
Effective mass is 10.96gr without cartridge.
Effective mass is 18.56gr with 6.5gr cartridge.
Best regards,

Haruo Uchida/sales manager
Therefore, previous info about the 26 grams of Jelco SA-750L is absolutely incorrect.
Regards, Andrew.

[NRG]

There is an effective mass calculator over on VE, you need the resonance frequency given by a test record, the cartridge compliance, cartridge and fastener mass. The resonance frequency needs to be quite accurate though, I ended up recording the resonance track whilst timing it from the start to the point at which the arm went unstable then analyzing the track in Audacity and noting the frequency at the timing point.

[Marco]

The resonance frequency needs to be quite accurate though, I ended up recording the resonance track whilst timing it from the start to the point at which the arm went unstable then analyzing the track in Audacity and noting the frequency at the timing point.

Yeah, for normal non-technical folks, that sounds like a piece of piss! :eek:

;)

Marco.

[NRG]

I like a challenge! :D

[NRG]

Actually you can get a fairly good idea without recording anything by using a 3~4" length of drinking straw taped to the headshell which gives an amplified view of the wobble and then noting how far into the track you get when it happens....I need to get out more LOL!

[Barry]

There is an effective mass calculator over on VE, you need the resonance frequency given by a test record, the cartridge compliance, cartridge and fastener mass. The resonance frequency needs to be quite accurate though, I ended up recording the resonance track whilst timing it from the start to the point at which the arm went unstable then analyzing the track in Audacity and noting the frequency at the timing point.

The effective mass calculator in VE is good enough, provided you enter in the required information as accurately as you can: effective mass of the arm (including the headshell); mass of the cartridge; mass of the cartridge fixings, and the dynamic compliance of the cartridge at ~10Hz. If the result lays within the range 8 - 15Hz, then one should not have a problem.

Ideally testing the combination using a swept-tone test track, or individual test-tone tracks, covering the range 5 - 20Hz is ideal, but in my experience (of over forty years), the calculated value is usually sufficiently good to know if there might be a problem.

[ehoove]

I finally stumbled on this:

http://audiosensibility.com/blog/faqs/what-is-the-effective-mass-of-the-jelco-750-tonearms/

Hope this helps,
Jim

Seems that due to the aluminum connector, the 750L 12" is lower in mass than the 750D with a brass connector. Interesting!

[ludovico]

I finally stumbled on this:

http://audiosensibility.com/blog/faqs/what-is-the-effective-mass-of-the-jelco-750-tonearms/

Hope this helps,
Jim

Seems that due to the aluminum connector, the 750L 12" is lower in mass than the 750D with a brass connector. Interesting!

I don't believe this data sheet, how can it be possible that the 12" is lower than the 9", it makes no sense at all.