Used in a mesa boogie F30 for some time.
I love the warmth and clarity of these lamps
They advantageously replace lamps Mesa amplification (stay on the lamp for the mesa however preamp section)
I tested a lot of lights before: therefore the Mesa (green, yellow), JJ (not bad but fragile) Cryo Harma EL84: good but colder than the Mullards.
In summary I would recommend to give more roundness and softness to clear sounds, distorted sounds are sharp and full of potatoes.