Another mystery amp

[Andresound]

It doesn't look like the "normal" way I've seen a Paraphase drawn, but I know that in either RDH3 or RDH4, there are a good 6 or 7 ways of phase splitting or inverting that are not seen commonly in guitar amps. I guess these days, there are only 2 in heavy use - Cathodyne & Schmidtt (LTPI)? Given the pros and cons listed for each, some of those unused ones sound like they might be worth considering in guitar amps. Fidelity? We don't need no stinkin' fidelity! So I shouldn't be surprised that a Mystery Amp has a Mystery PI.

Justin

To clarify: why it didn't look like a Paraphase to me is because it looks as though the full amplified signal of the first stage is passed straight to the grid of the inverting tube, without the usual voltage divider to knock the incoming inverting signal to the same level as the incoming non-inverting signal... weird, for sure!

There is a possibility I have drawn it wrong. I will check

[Enzo]

I wouldn't worry so much whether it looks "correct" for a certain type PI, but rather will the circuit work. Ther may be better ways or a "proper" paraphase might be different, but they could have purposely or ignorantly have designed it different. But it needs to drive one power tube with a signal and the other with its invert. SO we need to see if it will.

[Andresound]

I wouldn't worry so much whether it looks "correct" for a certain type PI, but rather will the circuit work. Ther may be better ways or a "proper" paraphase might be different, but they could have purposely or ignorantly have designed it different. But it needs to drive one power tube with a signal and the other with its invert. SO we need to see if it will.

Hi Enzo,
This circuit actually was a working amp. The cabinet was cheaply made, so I didn't expect much. Very distorted and no 'balls" with no sparkle/chime. Could very well have been "ignorantly designed". The HT is a low 290v. What do you guys suggest I change to temporarily improve matters. I will eventually use this chassis to build a 5e3 design. I already have OT and MULLARD OS 5y3 recto lying in waiting. Need to get a PT (325/325) in the new year.

[Andresound]

OK.. Have finally got a PT (unfortunately it's a toroid), but it will do. Stripped chassis and done a temporary board for 5E3.

[diydidi]

How did the amp repair come along? All good and grafting?

[olddawg]

From the tube complement he listed earlier it looked like an 18 watt Marshall setup except with 6V6s instead of EL84s and kind of a low B+. I would have put in an SS rectifier and made a Spitfire or something similar out of it.

[Andresound]

Hi Guys,
Been a while. I eventually built a 5E3 type amp into the cab. Was a quick rebuild on existing board. Amp worked, but was noisy. I have since built up a new turret board, so will revisit this project and post. I am thinking of a Tweddle Dee type 5E3. Thank you for all the help.