Expensive Tube Amplifiers

I recently visited Deja Vu Audio and was able to listen to 3 amps in a similar price range, Audio Note Oro, Soro SE and Western Electric 124. I was amazed at how good the WE sounded. I brought a second pair of ears with me and we discussed we would not converse during the 1st listening session. Both of us without hesitation liked the WE better. I know it’s subjective and there are flaws with the WE, a little bit of hum when right on top of the amp, but the sound is worth the negative aspects. So, I’m the newest owner! 
I don’t think age matters but quality of the design and parts. 

I keep hearing great things about the WE 124 amp.  Atmasphere mentioned an all-differential amp as a way to greatly reduce distortion, and there you have one right there.  I's build one for myself but it's really not enough power for me.

What’s strange is I had an 8 watt 300b that I ended up selling because of the lack of oomph for my liking. The WE 124 sounds like it has way more drive and power. I was looking to go to First Watt or Pass Labs but then heard the WE with very similar horn speakers and was impressed. Pre amp volume at 60% and WE set at 25% has my ears maxed out. I had to push the 300b to 90% and felt it started to tire and get loose. Perhaps it’s just synergy. Either way, happier now. 

I've been an Audio Research fan for many years. I never owned an Audio Research amp, because when I was buying an amp about 25 years ago, the Audio Research amps sounded bloated. I don't think they do anymore. Which means that Audio Research did a bunch of audio research in the meantime.

I have owned a number of Audio Research preamps. Although they're not amps, they will make my point. I owned a Reference 2 and Reference 3 preamp. The Ref 3 was a lot better. It had a much cleaner sound.

My point is this: I can't simply take on faith that somebody writing in this forum is a better engineer than the folks at Audio Research. So, if they keep learning and improving, I would have to assume that an amp of your design would also have shortcomings, and probably far worse shortcomings that the pros at high-end manufacturers.

It's like guys who buy drivers and build their own cabinets and swoon at the sound the way a father does at his newborn. If a company like Sonus Faber takes years and years to keep perfecting the integration of their drivers and cabinets, does that count for nothing? I own a Hovland Radia amp that I love, and Bob Hovland said it took him 25 years to design and build his only solid state amp. And he was a top-rate engineer. 

So, I don't take it on faith that high prices on audio equipment are not worth it. Or that a guy who understands electronics could build a better amp. Although, I do believe that if you build your own amp, you will believe it's better. And in that case, maybe it's worth it. 

As mentioned above 88db, 40hm not suitable for 300B SET, 845 is capable but you have to put up with great amount of heat, same with class A SS. I've had both, good for winter, for summer use need to look elsewhere. The other issue with these, heat is enemy of reliability, I experienced these reliability issues, when 845's let go you will know!

When choosing partnering amps and speakers, get the right tool for the job. SET's have to operate within certain limiting parameters, push them beyond their comfort zone and distortion rises exponentially. Transformers also critically important, undersized and cheap  you'll get greatly increased distortion and roll of in lower bass and highs, 3rd  order harmonic distortion levels also not great with these. Power tubes chosen also critical, quality tubes will provide lower levels of 3rd order harmonic distortion relative to 2nd order, also provide greater power output at lower level of distortion. And all this for naught if speakers chosen not compatible with these low power amps, think high sensitivity and benign impedance  curves.

As for expectation bias, I've built amps and modified many components, there have been regressive, lateral and progressive moves. While one can fool themselves in the short term, long term listening will tell the truth if one has quality references for sound quality.