Ok, thanks. I will not be using an AC voltmeter nor a scope (though I did by a true differential probe set, if it was needed), just the THD meter. Since it is floating, would anything bad happen if I ran it between 0 and 16 Ohm taps? I'm tracking on the amp schematics, but I really don't know what is happening inside the THD meter.
I've been poking around and building tube stuff for 16 years, but this amp has made me realize that there are aspects of electronic fundamentals that I accepted as convention without really understanding the underlying truths.
Again, thanks to everyone for helping and not treating me like the idiot I am!
V/R James
p.s. I had watched a bunch of youtube videos on minimizing THD with an O-Scope, but even the old-timers had some difficulty judging wave symmetry with just their eyes. That's why I decided to just use a THD meter.
p.p.s I have less hope than before that new tubes will fix the perception of weak bass. I told you all before that the power tubes were all old, but it turns out that just the VR series pass 6550 was old (GE 6550). The remaining 4 6550's are new production Tung-Sol 6550's, and the sticker on the base that I thought was an ARC sticker was actually a "tubedepot.com" sticker. None the less, they could still be 6+ years old, but I haven't bought a tester yet, so we'll see how well these new Telefunken (derived from JJ 65550, and cryo treated) tubes perform.
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