This morning I exchanged a bunch of new budget JAN GE 12AT7WCs and some used tubes for 5 pairs of tubes - a pair each of Mazda, Tronix, Belvu, and 2 pairs of the Miniwatt Dario. All of the tubes I acquired are used but were measured there and then, 4 pairs classfied as Grade A, a pair of the Darios graded B.
The Mazda kills the stock Psvane 12AU7-S.
Mid-range was fuller. Soundstage deeper and more precise. Bass is deeper and better defined. The tympani actually sounds like a tympani.
Prima facie, it looks like an unequal barter, but in reality it wasn’t. The JAN GEs I’ve tried to sell but no takers. The other tubes were well used so would be difficult to move on.
I’m happy with my trade. The M1200s sound like altogether a different amplifier, and a much better one too, at that.
I’ll tube roll through the other unlikely suspects and report back in due course.
On the basis of my trial with the used Mazdas, I’ll be confident to buy a couple of sets of NOS tubes.