Matching cartridges to Jelco tonearms - useful info

Yes and no. You can add weight and move to counterweight closer to the pivot to alter the effective mass of the tone arm, but it won't alter it by very much, so it will only move the resonance frequency of the cart/arm resonance by a fraction of a hertz and the difference between your 9 Hz and 9.4 Hz resonant frequency won't really be too meaningful. If you want a kind of one size fits all arm in terms of mass, you're probably better off with the lowest effective mass arm you can find with an changeable headshell or with some other way to add mass to the headshell and with adjustable counterweights. As an aftermarket matter there are lots of ways you can mod an arm to add mass to one part or another with lead tape or some other kind of inserts, etc. but not so easy to reduce mass, that's why as an aftermarket matter, it's probably easier to get to one-size-fits-all starting with a low effective mass arm.

 

Understood. I just never realized before that the counterweight would change the effective mass also, even if a small amount. After a couple of cups of coffee and more reading from above it has sunk in. I have used different headshells and headshell weights to mate arms & cartridges before. I wouldn't say that it's fun, but it's rewarding when you finally get a combination to sing.

 

I also recently acquired a NOS 370H and I have an effective mass calculator spreadsheet created by a guy named Luckydog from Vinyl Engine. Various components of the arm are weighed and input into the sheet and using this, I get an effective mass of 16.8g, with OEM headshell and no cartridge. YMMV.

 

You could also adjust it a bit by changing headshells with various weights. I've seen shells as low as 5g and as high as 18g, with everything in between. Standard Technics headshell is 7 gr, the stock Jelco one on the 750D is 12, on the 370H it's 8g.

Since the effective mass is computed for for the whole assembly, varying the weight of headshell can add/subtract handsomely. Just need to invest in a few headshells.

 

See, so the figure of "21" floating around again must have included the cart.

This thread didn't go in vain after all - collectively we figured it out. And I, for one, learned something. Thank you all.