Are EL34 based amps more musical than KT series based ? Or it's purely a matter of design?

Just a thoughtful guess but given the changes in sound when switching the same kind of output tube by different manufacturers, the make of tube may have as much influence on the sound as the tube type.

Design. 

Something from the guitar amp world. EL 34s have a different distortion signature to 6L6s - an evolved KT66. 34s clip more quickly but have a smoother distortion - think of a Marshall stack v a Fender Twin Reverb.

However, we use Marshalls because we want them to distort. Not something we look for in a hi fi amp.

300B / SET DHT bug hasn’t bitten me yet - it’s nice but I’ve heard no special magic I "gotta get". To be fair I like to listen louder than most audiophiles, and with more hard rock; the power limitation can cause some nastiness at higher SPLs.

I met Kevin Hayes at Sound by Singer (early 2000s), he opined that the 30/30 might have been the best sounding amp he had ever designed, but it was not a commercial success, he could not sell it for a price that was profitable.

I’ve heard exactly that about the VAC Renaissance / 300B lines, from multiple sources. They’re still sough after. The monos generate more power than most, and might be right up my alley, but I haven’t gone there yet.

But it’s also been a while since those days, and I can say that VAC’s KT88 based amps have come a long long LONG way since the past, even the 2000s (I used to have their little Auricle monos) - in both sound and price :(

RM-9 wrings quite a bit out of EL-34 but Roger was a genius… Like Gordon Gow and the 6L6 MC240… but really no meaningful conversation is possible without also considering the massively important imo ….output transformers….

@tomic601 I’ve always surmised that the MC240 would sound amazing to me. 40 watts is juuust close to enough for my needs :) I might have to try one some day. Yes, output transformers are crucial - avoid the bad ones - a lot of the good-rep vintage amps are renowned for their OPT’s (even Heathkit and Eico used Acrosound, Peerless). I imagine this is where the Chinese tube amps typically skimp. Some of the later Carver amps also got exposed for way undersized OPTs.

KT77 FTW