[stevehertz]

Not sure how much effect the rest of the valvestate circuitry is having wrt the sound of the ECC83, but from the time I did my very first test of swapping the crappy Chinese ECC83s in a Boogie V-twin rack unit for Mullards, the difference was literally night and day, unbelievable. What was gritty, harsh, discordant distortion was now sweet, harmonically rich and quite simply, nice on the ear.

Like I say, the ECC83 in the valvestate may, to some extent, be paying lip service to the valvestate sound, or it may simply be a decent ECC83 already in there. But yes, when you hear the difference, it's there in buckets, I've done it loads of times.