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RE: Please help with matching cartridge to tonearm.

Posted by mr.bear (A) on January 28, 2018 at 22:17:44

In Reply to: Please help with matching cartridge to tonearm. posted by twystd on January 28, 2018 at 10:04:04:

There is no precise way to guarantee performance of a given cart in your arm, vis-a-vis resonance. What I found about the Jelco SA-750-12 arm is that it's a high-mass unit, somewhere in the range of 30-35gm per some blog guy. That seems believable looking at the arm -- **see below. It sure is more than 10 gm someone mentioned!

The vertical compliance of the ZYX of 12CU nominally, and since its recommended tracking force is around 2gm, one might guess that it's measured at 10Hz but no source I saw confirmed this. Pressing ahead anyway, VinylEngine's resonance table for 32gm + 5gm for the cart (it's a light little guy!), 12CU results in 8Hz resonance. It's in the green chart area but about as low as you want to go.

So considering that the "real" dynamic compliance at 10Hz may be even higher than 12CU, the resonance gets even lower. That suggests the high mass of the Jelco is not too good of a match. But realistically, there aren't lot of carts way lower than 12CU. Just skimming VinylEngines cartridge database for MC's, some A-T's are under 10CU and might be a better match. Some Denons are nominally rated lower but may be more like 10CU at 10Hz. Benz and Clearaudio MC's are all rated nominally around 15CU. true the rating is not to an agreed standard but you have to live with it.

I doubt the re-tip would affect the compliance at all.

By 'live with it,' I mean this is a wholly theoretical argument about vaguely defined,highly variable parameters. In the real world (if such exists...) a cart's performance sure isn't 100% prescribed by its fundamental vertical resonance. It's very important, but for a good cart that resonance might be well controlled and have a less than disasterous effect on performance. I think you gotta' go ahead and saddle her up and get test record and see how she tracks. I'm gonna' put my money on it singing fine.

** The long 12" arm has a pretty high effective mass since it is longer and heavier and, as double-whammy has a high polar moment of inertia about the pivot. Extrapolating from some of my calculations I'm guessing as follows:
Headshell and cart = 60%
Armtube = 35%
Counterweight = 5%
My big-tube 9" Grace arm ran around 20gm (excluding cart); I could see that around 30gm for the Jelco 12" is realistic. Get the lightest magnesium headshell you can find.

Did you considered a Rega / Moth arm? I think they are pretty darn nice and you can find an RB303 / MK3 for ~ $400 I think, still. It seems to me to be sitting right on the sweet spot in the price/performance curve. I have heard them sing beautifully, set up well. I'm thinking its a nice match for the ZYX, but I'm basing on numbers and interwebbs data, so find some real inmates to verify.

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Kimber Kable

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