40+ watts SET, cost is not a problem

Pani,

Your speakers are not exactly easy to drive at 85db 4 ohms. I'm going to echo what many have already said, and that is you night not be happy with a SET amplifier.....you may have to drive it hard to get what you are looking for, and that may take the "magic" out of a SET amp.

You have some really good recommendations, and I'll add one more. I'd give Aric Kimball a call at Aric Audio (Google search for information), to get his input. He gives very freely of his time, and sells a bunch of amps you may want to consider: a couple of 300B amps, a 2A3 amp, the Transcend "Push Pull" (is what I own), a KTand a pair of monoblocks.....several might be excellent for what you are looking for. He also loves custom builds, many of his current lines started out as custom builds

I know you said no solid state, but at least look at the specs of the CODA S5.5 class A SS amp......I have had one for about a month, and it's truly amazing; huge current delivery on hand

@brandonwade ,

Tap any post and a ’report this’ icon will appear. It will tell you to select a reason it should be deleted. One of those reasons is ’it contains profanity’.

Your foul language is against forum rules.

Capeesh?

"What’s most disturbing is voicing a $30k Amp through a pair of Tektons…."

😂

I have owned a 300b SET for 15 years and simply love it. However any DHT can be utilized in a SET amplifier. 2A3, 45, 211,805,GM70 etc. SET is not limited to300b.

@charles1dad 300b is about as powerful as you can get and still claim hifi bandwidth. The thing is, if the amp doesn’t employ feedback, you’ll get phase shift down to about 10th the upper cutoff frequency (-3dB point) and 10x the lower cutoff. This is filter theory.

The ear is terrible hearing phase by itself, but over a spectrum it can interpret it as tonality.

Phase shift in the bass due to a cutoff frequency not low enough is audible as a lack of bass impact. Phase shift in the highs due to a lack of HF bandwidth is heard as a darkness. So you need bandwidth well beyond the audio band to really get this part right; with no feedback ideally 2Hz to 100KHz or better.

@atmasphere @charles1dad @jond and others, it seems people are not warming up to the idea of SET here. And also there seems to be very few seriously good tried and tested choices beyond 25 watts. So what are some really good options for push-pull tube amps operating in class A with zero negative feedback?

@pani There is nothing wrong with feedback if its properly applied! The problem is, it usually isn’t. As a hint you can’t apply it to the cathode of an input tube since that tube will distort the feedback signal. That will cause IMD and higher ordered harmonic generation, both of which are not musical. This is one of the reasons feedback has a bad rap, but its not feedback’s fault so much as poor execution.

An advantage of zero feedback though is you get a ruler flat distortion vs frequency curve. This is important; if there is a rise in distortion at higher frequencies the ear will interpret that has harshness and brightness because the harmonics will not be masked (as they usually are in an SET). I know a PP amp that is zero feedback isn’t that hard to find. Take a look at the ’300b lovers’ thread on this site.

If you do feedback correctly you can get a ruler flat distortion vs frequency curve just like a zero feedback amp, but with lower distortion overall; just as smooth as any zero feedback amp, just as laid back, but with greater resolution since distortion obscures detail.

@atmasphere

300b is about as powerful as you can get and still claim hifi bandwidth. The thing is, if the amp doesn’t employ feedback, you’ll get phase shift down to about 10th the upper cutoff frequency (-3dB point) and 10x the lower cutoff. This is filter theory.

On technical grounds I won’t even try to dispute what you stated. I can only rely upon what I have heard. I’m very familiar with in particular two PSET 845 amplifiers (50 watts for each pair) that could suffer the bandwidth limitations you mentioned. I can genuinely say however that both of them sound superb and so natural reproducing music.

I am referring to the Absolare Passion 845 mono blocks and the Viva Audio Aurora 845 mono blocks. I don’t know how they conquer/manage the potential bandwidth limitations. I can attest that listening to music, Both are stunningly terrific! No doubt their respective designers/engineers could explain how they accomplished this.

Charles