The Mullard 12AX7 / ECC83 Reissue is a nice vacuum tube but in my opinion better suited to home audio than guitar amps. The tubes have well balanced triode pairs and a very even flat response. Compared to a Tung Sol it sounds a bit flat, but so does a NOS Mullard. Microphonics is not an issue despite the larger that average plate structure. The transconductance on my sample was the same as two NOS samples I measured. Not really high gain at all, but a real good noise floor and a nice smooth tone that doesn’t encourage ear fatigue the way some preamps can be.
The Tung-Sol 12AX7 is my favorite preamp for guitars because it accentuates highs and lows. The Mullard 12AX7 amplifier tube adds virtually no tone coloring and is smoother sounding to my ear than a JJ ECC83S. For hi-fi gear the Mullard will likely be a winner but there are better choices for guitar amps for less money.
Thanks for this article.
Many thanks you your analysis John. Most of my 30 years R&D was with transistors, but I do know the difference between a KT88 and a KT44! Memories of someone in a local shop being sold a KT88 to replace a dead KT44 – yes really – I don’t know what would be worse – the lope-sided response or the dc component through the output transformer.
These days I’m using retirement to complete some books and other projects – I know that one day I’ll drop my TUBE MP and so upgrading the tube and keeping the original as a spare would be good insurance. A new tube should last to the end of my days.
And thanks for the link – I’ll ask “She who must be obeyed” to order one. gk