SET the best?

My 300B amp measures flat well below 30hz.

To play the bottom octave properly you need bandwidth to 2Hz. This is because once the amp starts rolling off, it does so at 6dB/octave. When you have a slope like that it causes phase shift to be present up to about 10x the cutoff frequency. This is basic filter theory. So 2Hz bandwidth allows for 0 degrees of phase shift at 20Hz.

The ear perceives phase shift as a tonality. In the case of bass, its perceived as a lack of impact, as a thinness in the sound.

In the case of a 30Hz rolloff, the phase shift will go as high as 300Hz. As a side note, speakers are not part of this phase shift issue- its something that applies to electronics.

You can get around this problem if you have enough feedback. If you have enough, the feedback can correct for phase shift.

That kind of feedback isn’t available to SETs or for that matter, most tube amps. So bandwidth is the only way to solve the phase shift issue.

OK listening and thinking things over

SET vs PP

With jazz quartet, light jazz such as Sophie Milman, Diana Krall, classical chamber, solo piano/violin

~~~SET gets the Cuban Cigar

For large blues/jazz swing orchestra/large symphonic orchestra,

PP gets the Cuban Cigar.

https://www.youtube.com/watch?v=4XTmQHjF0e4

Can't put in one basket. 845 300B, 2a3, and then added variable of loudspeaker. Find the right combo, experience live performers in room every listening session.

@mozartfan ,

in the video running both a coax tweeter and a second tweeter in paralell off-axis will reult in a blurred soundstage, partial cancellation of frequencies through overlap as well as issues of phase coherence. I’d suggest to use a supertweeter with the Coax driver instead. On bass, similar issues apply although localisation is less critical. The SET looks intereting and you rightly point out the importance of transformers.