I need help diagnosing a sibilant problem on vinyl

I would suspect a damaged stylus first, from experience this was the cause of such sibilance in my cartridge many years ago.

Doug, There's not too many adjustements you can make with Rega arm. Proper alignement, VTA and nothing more to adjust there. If gazilions of trial-errors made and still the damn sibliance, than it's time to inspect the cartridge.

You can add inadequate PS filtration in the Phono Pre and the rest of the chain to the list. I have become aware of this over the last year or so. My DIY gear (all K%K Audio fully differential designs) use active constant current sources in series with the B+. A resistor shunts a small amount of that current to ground establishing the B+ voltage (V=I*R, ohms law). These active CCSs have a very high AC impedance. One would think that very little crud would get through. However, replacing the shunt resistors with active shunt regulators made for a huge difference in clarity and yes, a reduction in apparent sibilance. The first shunt regulators used a simple JFET in series with a resistor to set the reference voltage for the shunt device. A second generation shunt reg. used a LM-334 current reg. wired as a zero temperature coefficient current source cascoded with a MOSFET (cascode current sources almost always perform better than single devices). Again, more transparency and less sibilance.

Recently I upgraded an early but fully modded K&K Maxed Out SE phono pre for a friend. This unit has active constant current plate loads on all the tubes. One might think that adding a current source fed active shunt to the B+ supply would not make a huge difference. It did, by a large amount.

I guess the take home here is this: no matter how much filtering you have in your power supplies, crud can get though and muck up the signal. I'm not a big fan AC power line filters as I think this should be addressed in the design of the equipment itself; but if all else fails you might try it. I would suggest you borrow the clean up filter first and try before any purchase.

Nine times out of ten lowering the rear of the cartridge (SRA) will cure that problem.

Doug, There's not too many adjustements you can make with Rega arm. Proper alignement, VTA and nothing more to adjust there.

Regas aren't the most adjustable arms, but in addition to alignment one can certainly tweak VTF and anti-bias. IME, these are the three tonearm adjustments most likely to affect (distort) the reproduction of sibilants.

My prime suspect is the cartridge, but before dropping money on an upgrade it would be prudent to eliminate user adjustments.

One more possible cause: a dirty stylus. Is the stylus cleaned after each side (preferably with the Magic Eraser method?)