I assume your comments about semiconductor diodes and constant current sources are in reference to the Bottlehead Paramour amplifier and maybe others like it. I have a couple of Paramour amplifiers, and while they aren't entirely quiet, it seems to me that the problem is with rectified line cycle hum and a little bit of high frequency switching artifacts. Stock Paramours have a touch of hum and buzz.

The Paramour is an entry level kit. As such, I suppose some cost-saving measures are in order. Personally, I would have liked to have an all-tube kit, but more for consistency than for performance reasons. It just seems cool to me to be all "old-school" running all tubes than to have a mix of tubes and solid state in the circuit. But the Paramour saves maybe twenty bucks or more by using a couple of ten cent 1N400x rectifier diodes and inexpensive electrolytic caps for the DC supply. It was probably done to keep costs down, and it seems to work just fine.

If anything, I think the biggest problem with this amp is that there is not enough power supply regulation. I'm not as concerned with what is used to regulate power supply voltage as the fact that it doesn't appear to have adequate regulation. But then again, it is an entry level kit.

I think it's really cool to have an amplifier with no semiconductors at all. So I think it's cool to use tube rectifiers in the circuit, and to build a noise-free amplifier using them. I consider such an amplifier to be an impressive piece of hardware. But to tell the truth, I'm not sure I would expect to find any performance penalty when using semiconductor rectifiers or regulators. In these places, I would have expected using semiconductors would be an easy way to get the desired goal. Some might see it as kind of like "cheating" but I would have expected it to work well.

Seems to me that shunt capacitance in the power supply should really knock down the ripple pretty well, and that caps across the diodes would help remove the switching noise. So I'm not sure I fault the diodes used as much as the lack of adequate filtering. Add a few more filter caps, and it probably would quiet down a lot.