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

Then maybe I should upgrade output transformers in my VAC Avatar with custom ones ? This is a crazy idea, I think.

@inna Could be... The output transformer is the most critical part of any tube amplifier. Its only crazy if you think so... You could easily wind up (if you see what I did there) with a garage full of prototypes trying to get it right.

The higher the amplifier power the harder the transformer is to do. It is exactly this reason I designed OTLs instead and prefer smaller tube amps if transformer coupled.

Then maybe I should upgrade output transformers in my VAC Avatar with custom ones ? This is a crazy idea, I think.

Inna case this was serious - don’t do this. You’re not going to out-expertise nor out-voice Kevin Haye’s choices for his own amplifier. You can certainly out-budget him within the context of an Avatar SE, but at that point - just explore any of VAC’s newer, more advanced models released since the Avatar.

"Then I can’t use my Mullard EL34". Yep! Them’s the breaks. Kevin’s done wonderful things for KT88 tubes since then (pricey, though).

Final thoughts: don't do this.

mulvelimg, you are right of course. I have no intention. Upgrading to newer VAC integrated might be a possibility for a more distant future. But I like this one and would probably go with separates if decided to upgrade. I won't give up my Mullards easily, you are right about this too !

Different thing perhaps but I have a custom dual voltage transformer in my Nakamichi 682ZX deck. Willy Herman, a famous Nakamichi technician, had a few ones and installed it in my deck years ago. The deck does sound a little better with the custom one but the difference is small. Willy said that the quality of this transformer was much higher than original Nakamichi.