I started this thread due to a couple OT posts lately that had me spending a lot of time researching this today and would like some feedback/conversation on the topic. Please chime in on anything that doesn't look right. For the PP 6v6 Tweed amps - Harvard, Vibrolux, Deluxe, Tremolux - I'm seeing that they ALL used the same OT, either the Triad 108, then to the Schumacher 125A1A in the late Tweed amps. The difference in output between the model lines is dependent on the choice of PT with them all - current rating & voltage. So, the 10W Harvard and 18W Tremolux used two 6v6 power tubes and the same OT, but the power transformer obviously made the difference, and rectifier in the Tremolux. The next stop is that the Triad 108 was an 8k primary, the 125A1A was a 6.6k primary, the 6.6k giving more clean headroom and higher output. Both appear to be similar size and bolt spacing. ClassicTone lists both their models for these as 20W transformers, practically the same dimensions, but the respective primary differences - 8k vs 6.6k. What was eye-opening to me was that the Hammond 1750E (listed as 8.5k) I've always used in any of these situations that they list as a Tweed Deluxe or Princeton Reverb OT appears to be a copy of the later Princeton 125A10B OT. It's smaller than a vintage 108 by a 1/2" in some places, and the bolt spacing matches the PR, but not the Deluxe. It is certainly smaller than their 1750H which is their 125A1A model replacement, and it is a 6.6k primary. So, it would appear that all of my builds using the 1750E OT - including my 5e3 - are essentially using a Princeton Reverb OT, not the Deluxe OT I thought it was. That being said, I don't think I've never finished one that I wished was louder, cleaner, or that it had more bass response. And it looks like Hammond needs to design an 8k version of the 1750H DR transformer if they want to really offer an authentic Triad 108 replacement.