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Does 21g seem high for effective tonearm mass?

Hi there, I've been looking into these somewhat popular Jeclo tonearms. Actually the 10" liquid dampend unit SA-750e. I've got an email from Jelco and the effective mass is 21grams. Does this not seem shockingly high compared to nearly everything else on the market these days?
I plan to mount a Sumiko Celebration on it but I'm not so sure about the match. It seems this arm may be limited to cartridge choice and that would be too bad.
If anyone can shed some light on this it would be appreciated.
My other options for arms of course would be the Rega/moths, Hadcock and I can get a pretty good deal on a VPI classic arm.
This wasn't supposed to be confusing at all as I was taking a step away from my ET2 and trying to simplify my setup. Now it seems I've opened a can of worms
alun
lewm
12,459 posts
 
IMO, you don't want the tonearm to "control" the cartridge. You want the tonearm to allow the cartridge to ride as smoothly as possible through the curvaceous and treacherous grooves of an LP, without bouncing out. At the same time, the tonearm should not impede the cartridge. It's a tricky deal.
dcbingaman
93 posts
 
If the cartridge compliance is low enough to cause the arm to move rather than the cantilever to move when the groove undulates back and forth, you get no coil velocity in the magnetic field and hence no signal. This happens ALL THE TIME with low compliance cartridges and too light tonearms on low frequency undulations. Hence light tonearms can sound lightweight.

Same goes for unipivots with too low a moment of inertia in the azimuthal axis. Because the groove is offset (below) the CG of the arm / cartridge, the groove will rotate the ARM back and forth about the unipivot point, rather than move the cantilever. That is what I meant by having the arm control the cartridge instead of the other way around. Gimbaled arms and linear trackers don't have it's extra monkey motion and have fewer problems reproducing low bass as a result.
vertigo
130 posts
 
Matching arm to cartridge is all about allowing the cartridges motor to get excited in an optimal fashion, such that the cartridges virtues are realized mechanically and electrically.

An analogy would be to match a bikes frame weight to tire pressure. If you have a bike frame that weighs 200lbs! what will happen to your ride? It will get hard and bumpy if the weight overcomes the counteraction of the tire pressure.

So the right frame would be not too light and not too heavy RELATIVE to the actual tire pressure quotient (whatever it is) so that you get a NICE ride.

Not all tires are designed to work with the same tire pressures, so too with cantilevers "springiness". Some are stiffer and need just the right amount of weight to have a good ride. Remember over inflating the tires on your bike? It was a hard stiff ride. Too flat and the bike was sluggish and hard to pedal.

So, it's not about one controlling the other but about choosing an arm which will allow the cart to work within it's intended parameters so that it can sound it's best. Its about an ideal physical relationship to achieve a desired goal.

Once you've done that...don't forget to match the output of your cart with the input of your phono ! so it too is just right.

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