Tube pre for class d recommendations

Interesting Ralph.
I have 2 foundation research LC2...one grounded and the other lifted ...done by Ed....that I used. Meaning, I was really giving it the old college try to make it work.

Lifting grounds is not going to do it with the UV-1 since its really hard to ground loop it through the power cord.

We did run into a hum problem with a dealer of ours that was using a Topping amp which is class D. The amp was only $80.00 on Amazon so I bought one but could not duplicate the complaint with his UV-1 or any that we had here in the shop. My best guess is that there was something wrong with his amp but its all water under the bridge so I don't think we'll ever know. Otherwise we've been able to solve all the hum problems we've encountered with the UV-1 except for that one. The dealer sold that preamp and the customer seems to like it a lot.

The UV-1 has an aluminum chassis and a steel bottom cover. It can hum if placed near a power transformer or the like since aluminum does not shield at audio frequencies.

Just give it your best shot. Pay attention to input impedance of your amps- some tube preamps can't handle input impedances much below 30K or so! There are tube preamps that can handle low input impedances in amplifiers with no worries.