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

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.

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

Larry, I see.

So, as important as it is, design is not everything. Tube types have intrinsic qualities.

Larry, what speakers do you run with that 349 tube based amp ?

Ralph, I see.

Some people will just listen to 300B based amps and nothing else, I heard.  They consider 300B to provide the purest midrange of them all.

If midrange is not right, the rest doesn't matter.

Power cord can make quite a difference for dynamics and bass, by the way. I use older Purist Audio Dominus Ferox, appears to be a perfect match.

mulveling, "ain't cheap" is an understatement, VAC's top and near top of the line separates are extremely expensive, but you say they are worth it.

I have no complaints regarding the dynamics and bass of the VAC Avatar SE EL34 based integrated. I suppose, it also depends a lot on particular signal tubes that you use. These 60 watt/ch in ultralinear mode sound quite powerful.

So, there is something inherently very musical in EL34/EL84/6L6 tubes.