SPU Royal N

Continuing the discussion from Linn LP12:

I’ll take this out of the LP12 thread as it’s rather too tangential.

I’m assuming that the resonant mass of the tonearm/cartridge is the key to getting the best of an SPU. I have somewhere in the region of 34g from the effective mass of the tone arm(~10g), the brass mounting plate(8g), cheese(3g) and cartridge(12.7g), plus screws and the counterweight is a long way back. However it seems likely that Naim would have followed this path too and they still didn’t find the Royal N fully satisfactory on an Aro. There could be something in the way the two arms handle vibrations from the cartridge.
Another thing is the fineness of adjustment available, I have a sub counterweight for fine VTF and a small Allen headed grub screw to wind VTA up and down as well as fine control over bias, all of which give an audible effect from very small adjustments when near the optimum (the down side is the bias and VTA go off a bit with changes in humidity). The adjustments on an Aro are that much cruder so possibly harder to hid the spot.
If I do get a brass cheese made up to around 11-12g to suit my Schröder it would also give around 36g effective mass for an Aro, which is spot on. I may have to use both extra rings on the sKale to balance it. Trying it will be difficult to resist. I have a slight doubt as to whether the Aro’s bearing would take it though, that’s quite a bit more than was planned for.

At Naim we got no further than a heavy counterweight and a little extra mass on the bias weight. It was rather good in many ways, but we would have liked to look at dispensing with the cheese piece and making it all of a piece, as it were, but the project got rather overtaken by other things.

So room for manoeuvre without just repeating previous work. Of course it is rather a dead end but it won’t cost any more to give it a try, unless it wrecks the pin or cup in the process and I think I’ll get away with it if I’m carful about placing the arm top so it doesn’t clonk down into the well from the edge of the cup.
The Royal N is proving to be something of a bargain for the musical rewards on offer, at least in its current setting.

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