Jelco effective mass

[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!



Marco.

[NRG]

I like a challenge!

[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/faq...-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/faq...-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.