"** So that would include all the Phase Linears and of course Naims.

FYI: These amps lacked output Zobel inductors.

FYI-2: Later piezos included 33ohm series resistors or tiny lamps that helped. "

Then that would include my 400-2.

However, I found a page a while back that said that coil there is not correctly referred to as a Zobel. It's not a big deal.

Had a Sony reel to reel a long time ago, had speakers. I decided to hook it to my Peavey T-1210s. They had a bank of three peizo tweeters per, and all that thing did was hum, so of course I disconnected it. It was the bias oscillator leaking into the output.

"BTW: I have done 4 cycle tone burst tests on various piezos and lemme tell ya the results are not pretty. "

Oh, I'll bet. The things are not known for real high fidelity, to say the least. Anything peizo is non-linear and if you need anything in audio, it is linear.

I am surprised they got ceramic phono cartridges to work so well. In fact years (decades) ago I had a situation where I had a ceraic cartridge and a magnetic input on the amp. I shunted the cartridge with a resistor, I do not remember the value. It also seemed to take off the rolloff of the cartridge which normally would make RIAA EQ unecessesary. It actually sounded good going through an RIAA EQed preamp. It was an Astatic 353D IIRC. I don't remember what kind of amp, but back then I was in the amp of the week club.

But a peizo tweeter, it almost only puts out noise. If you want to claim the response and have a hot high end, cross them over at at least 8KHz, which puts second harmonic at 16 KHz. Most people will never hear it. Use a horn for up to 8 KHz if you are looking for volume.

And I do like the 33 ohm series resistor idea.