300B or 2a3 SET Class A for Heretic Model A?

@alexberger I tried Coincident Frankenstein's with Altec Model 19's, thinking that the Altec's 99 dB efficiency would pair nicely, but unfortunately, the Frank's made the 19's sound under powered.   It's possible that the 19's impedance curve is demanding, as I've tried numerous amps, many of which didn't seem up to the task, as the sound was lacking in bass and dynamics.  I'm currently using McIntosh MC-30's and they are the best I've found so far.

Hi @pdreher ,

What is a size of your room?

In room smaller than 250 sq. feet 300B amp should be enough. I had opposite experience with McIntosh MC 30 and DIY 300B amp with my Altec 604E. But the room was small and probably 604E is a little bit more easy to drive versus model 19.

But I liked a lot MC 30 with Spendor 2/3 in the same room.

I don’t recall not liking a speaker because the amp had too much power but I’ve heard plenty of underpowered speakers sound bad. I’ve owned speakers that were 105dB efficient and sounded dull and lifeless with a variety of flea powered SET amps, along with PP amps of modest power ratings. It wasn’t until I hit them with 200 quality, clean, digital watts that these things really came to life.

That’s been an experience I’ve had multiple times over the years with different speakers. I own Audio Mirror SET45 monos and they really sound fantastic going into a 98dB speaker, but dull and constricted into an 89dB speaker in a modest sized room, even though their power rating suggests otherwise.

 I agree with Ralph that running the amp so it’s maxing out at around 25% of its rated power is a good strategy with SETs.

 I also have parallel KT66 and KT88 PP amps that are more tolerant of being driven closer to their max rated power. 
It’s really about experimentation and finding the right synergy, which will be dependent on your room size and geometry and your personal listening preferences, not something that someone can tell you on a forum.

 I also agree with the poster who said running low powered SETs gets you entrance to a cult, and it’s one where you can land on some magical combinations of speakers and amps. 
It’s all fun, so long as you don’t mind losing your eyebrows every once in a while.

 I also agree with the poster who said running low powered SETs gets you entrance to a cult, and it’s one where you can land on some magical combinations of speakers and amps. 
It’s all fun, so long as you don’t mind losing your eyebrows every once in a while.

Its really about SETs being a musical instrument rather than a music reproducer. Fun, but its not at all accurate to the recording. That profound ever-lovin' 2nd harmonic gets a richness that isn't part of the original recording; that is why I say 'musical instrument'.

@alexberger my room is not small @ 14' x 26' x 7.5' tall with a 6' wide opening that leads to an adjacent room.   My Altec's use Werner Jagusch crossovers, so it's possible they are contributing to inefficiency or negatively impacting the impedance curve, more so than the original stock crossovers, but I can only speculate.  In addition to the Franks, I tried an Elekit 300B amp and it too struggled to drive the 19's.  I did try a Line Magnetic 845 based SET integrated... and while it did sound fantastic in many respects, it emitted loud buzzing sounds from both the speakers and eventually the transformers... so as much as I would have loved that combo to work, the buzzing and transformer noise was a show stopper.  I'd like to try another 845 SET amp with the 19's again down the road... thinking Mastersound Compact 845, deHavilland Aries or Audion Shadows.