What Is This?

Today I just received my SFP that I purchsed on ebay, and this Groove Tube thing is in the 5U4GB tube socket. How will this affect the sound of the amp? I would think an actual tube here would be better.

Looks like a potted solid state rectifier module to me. Made to be plugged into the tube socket for the, uhhh, tube rectifier (I know, DUH! :oops:).

Sound differences? I dunno; I haven't experimented with tube vs. SS rectifiers. Others here know though ...

Supposed to improve sustain I think...

Solid state will keep the circuit more stable and cause less wear and tear. It also seems to tighten up the bottom end.

The tube rect will cause the power tubes to sag when strained and give you a more compressed sound.

This is the non-technical answer.

Yep.

A solid state rectifier that fits in a tube rectifier socket.

There is also a groovetube GT 7025 tube in the 7025 socket. What kind of pre amp tube can be substituted here? My understanding is that the 7025 is a low noise 12AX7. Are the 12AX7, 12AT7 and 7025 inerchangeable in this location? I have a full set of JJ tubes that I got for my HRDX from Eurotubes.
I have 2 6v6's, and ECC83S and ECC82S's. I think I can use these in the Princeton. The amp came with Electro Harmonix 6V6's. Are the JJ's better?