But to be honest, I’ve been wondering by myself what kind of amp it really is. It is provided with the same power tubes as a Marshall plexi: the EL 34. The reason was all the famous groups like The Beatles wanted louder amps and Vox had to meet their needs building amps that were louder than an AC 30. Since the AC30 has already a quartet of EL 84 (which are rather low power, but high sound quality), the consequence would have been an octet.
This being rather expensive, and developing much heat in the chassis, they decided to build an amp with different power tubes. Some people assume an AC 50 is nearly the same as a Marshall plexi, but it is not.
There is this roughness in sound, that’s true (a typical Marshall trait), but to my knowledge the amp’s design is completely different. As usual, the entire band would use the same amp in the sixties, except those who were successful enough to buy a stack for each member. So there is a “normal” channel that would provide enough low end for the bass player or for the rhythm guitar (they had this dogma in mind: rhythm is dull, solo is bright).
And there is the “brilliant” channel for solo instruments, which can be really biting! What I found out about the sound is, it is barely balanced. Some bass frequencies tend to dominate, others not. With electric bass my sound somehow got out of hand, and so I preferred my SWR amplifier.
The tone stack is very effective, as one might know from other Vox amps; the knobs are interactive, so you can get a great variety of sounds. With the brilliant channel I had to cut down treble.
But on special occasions this amp is unbeatable! I love the crazy subtones when playing two notes at once with distortion, and I love how the wah-wah sounds with this amp. For reasonable sound pressure levels I use a power soak, and for distortion I prefer a treble booster with inbuilt fuzz.
That’s what I can tell from my own experience. Hope it helped.