Hmm. Yes, the 6v6 amp. I'm still learning, so not totally clear on "which" ma tube spec you're referring to. I'm using Hammond 1628SEA output transformers on the 6v6 amp (not the GXSE15-5k ot that Jurich listed).

Love the Gold Lion tubes. I'm curious about the transformers. Are those off-the-shelf that you painted? I'm using Tung-Sol 7581 tubes in mine, and thinking about getting a pair of KT66s to roll into it. What do you think of that? I also just built a little SET amp based on the Decware design. Uses SV83 tubes in the power stage. Sounds truly amazing! (I have folks now that want to buy my builds too - I'm going to be busy! Using the name Armadale Designs (AD).) )

Hi Danny - good idea to roll tubes (shoulda thought of that). If I understand your question freq response, it's in the doc (and to me, looks amazing!). I'll find some time to run the tests again at full volume (and swap tubes).

Ok gang, see attached. I took the plunge on the Audio Analyzer suite and the Digilent Analog Discovery 2, and tried it out on this amp. Here's what I got on the first (and only, thus far) pass (attached). The screen captures are a bit truncated so I added some text to help with that. So, a few things: 1) any input/feedback at all is appreciated 2) question: on the THD test, there is notable difference between L and R channel. What gives? I certainly can't hear any difference. Tubes maybe? (Although my output tubes are "matched" supposedly.) And, what do you think the cliff at 10kHz is..? 3) frequency response curves are pretty amazing... is this real? (I will say, it jives with what I'm hearing, as best my ears can tell..) 4) THD vs. power... once again, L channel is higher. Thoughts? Thanks! I love this forum!

Ah! Perfect! Thank you...

I use both 18 awg stranded and 20 awg solid, in various places.

aha, I see - thanks Danny! Yes, that was just before clipping. (I was using the old "x .707" rule, but forgot that is based on peak voltage, not p-p...) I have a related question: the OT on this amp has multiple impedance sec taps, so I installed speaker jacks for both the 4 ohm and 8 ohm taps. In the case of this particular test, I think I had my dummy loads attached to the 8 ohm tap, but it's actually a 4 ohm dummy load. So, how does that confusion play into this math? thx!

Oh, one more note... I accidentally had the input signal probe set on 10x, so it's really 2vpp, not 200mv.

Initial o-scope tests look pretty good to me... (Kinda wondering why input and output are out of phase, but I have two thoughts: 1) so long as both channels are the same it doesn't matter (?), 2) it's a 3-stage amp, so perhaps this is expected..?) I'm getting approx 11W RMS output, I think.

@Audio Valve Nut (and anyone else that cares to weigh in).. re Isolation Transformer. I stumbled across Stephe's mention of using that in one of her videos. I'm kinda scratching my head because as I read on-line about these things, the comments and opinions, and prices, etc. are all over the place. (I suppose that's case for a lot of things these days.) Can you or anyone kinda boil down using an isolation transformer for the purposes of building vacuum tube amplifiers along the lines of the Skunkie designs work? I understand the purpose in a general sense, but have gotten a big confused by all the on-line chatter I've read. I'm about to embark on a build (I have nearly all the parts now) of an integrated amp (not a Skunkie design, but similar), from scratch, and I'm relatively experienced with electrical engineering and assembly / troubleshooting / repair, but not as much with vacuum tubes. I have a variac, DMM, will be picking up a scope and signal generator (I'm familiar with use of all of these). But, my investment in starting build amps is getting pretty costly, and just wondering if I need to drop more coin on an isolation transformer. What I'm looking for is (for the isolation transformer): a simplified statement of purpose (relevant to this work) how critical is it to have one for this kind of work? what are the features that we want and don't want (like I get some have isolated grounds and some don't)? any recommendations on which one(s) to buy? can these be done as a DIY to save $? or does it end up costing as much as a purchased unit Thanks!! Don

All really great info Danny - thanks for sharing!!

Well, I have the very same question. One possible solution is this. But, it also looks like a very simple DIY project... I would suspect there may be a more elegant and simple add to the project. https://www.crutchfield.com/S-Bm3r3n8a7nm/p_543ADP12/Russound-ADP-1-2-Speaker-level-to-Line-level-Adapter.html?XVINQ=GLX&XVVer=FOL&awcr=50190041905&awdv=c&awnw=g&awug=9009674&awkw=aud-439295825974:pla-78572876905&awmt=&awat=pla&gclid=CjwKCAjwyaWZBhBGEiwACslQowqkyctRrRmrWk4Vt7V1q47DGDNyi22kCT8HCTCZHKnUSAz0--K0TRoC1LUQAvD_BwE