Phono Stage upgrade to complement Dohmann Helix One Mk 2

@drbond , The stock counter weights are brass. It is a slightly different alloy from the stock I have access to. The counter weight should be within a centimeter of the bearing housing. If it is farther away you need a more massive weight. 

@mijostyn 

Sounds interesting, but I would think that it would be simplest to use a lighter cartridge mouting plate and move the counter weight forward based on that as opposed to adding a heavier counter weight, which would then affect the effective mass of the tonearm in a more difficult way.  

The Schroder CB manual says that the effective mass of the 11 inch tonearm is 17g.  However, it doesn't say at which distance from the bearing housing that calculation is based upon, but I guess it doesn't matter that much.  So, getting a heavier counter weight would allow me to place it closer to the pivot point, but then that would lower the effective mass of the tonearm, which would affect the interaction with the compliance of the cartidge.  I don't see how a tonearm with a lower effective mass is neccessarily better than a tonearm with a slightly higher effective mass. 

Does the CB manual state whether the value of 17g is inclusive of the weight/mass of a "typical" cartridge and mounting hardware?  If not, then add the weight of the cartridge plus hardware to the figure of 17g.  I enjoy the math and science of this stuff, but in all honesty, on a personal level, just make it work and enjoy yourself.  I don't know where you were going with your question about the brass, but for sure the material used for the CW makes no difference to SQ.  The density of the metal might come into play where you are concerned about the size of the CW, in order so it fits as close as possible to the pivot.  In that case, density is the parameter to go by, but at the same time, I say don't bother.

@drbond, ​​@lewm is correct. However the critical issue here is the resonance frequency of the tonearm-cartridge combination. A given cartridge is going to require an arm of a given effective mass. Since you can not adjust the cartridge you adjust the effective mass of the tonearm. In the case of the Schroder CB you can do this with different mass cartridge mounting plates and different mass screws or even headshell weights. You then position the counterweight to achieve the correct VTF. With the Schroder you have the choice of several counterweights. With a heavier counterweight you will move it closer to the pivot to achieve the same VTF. This also keeps the arm's effective mass exactly the same, but what it does do is decrease the arms moment of inertia which improves the arms ability to track warps and eccentricities. 

Never set up an arm by specification. Set up and arm by testing. Equations are close to worthless when it comes to adjusting the resonance frequency of a cartridge-arm combination. There are too many variables involved. The specifications are ballpark only. You get a good test record and learn exactly what the resonance frequency is and make adjustments as required. I always shoot for 8 Hz and will settle for a little below but never higher. I also balance my own wheels.

@mijostyn 

Ah, so that makes more sense:  you're not looking to necessarily change the effective mass of the tonearm, just its tracking ability, by decreasing its inertia.  

What type of terst record do you use to measure the resonance frequency of your set up?  (I don't think that the AnalogMagik does a good job at determining resonance frequencties, as every reading I've gotten from that portion of the software is way off the charts, in which case it says that the result is worthless.)