Ampeg V4 stack with 2 4x12 cabinets. I saw the Stones with Mick Taylor and they were using SVT's and V4's. Just incredibly good sounding bass and guitar sounds. So, I found one for sale and bought it. I thought there was something wrong with it when I got it because the tone was odd for a guitar and it was too clean. It sounded like a solid state amp. I used it at rehearsals and at gigs, fiddled with the controls constantly and couldn't get that great rock crunch like the Stones had. I found the phone number for Ampeg and called them. (this was in the early 70's. No internet, not that many amp repair shops.) The friendly amp tech they put on the phone told me that the Ampeg V4 has a Baxandall-like tonestack with 3 switchable EQ frequencies: 300, 1000 & 3000 Hz + TMB mid boost knobs which are flat @ 12:00 o'clock, so you can boost clockwise or turn down counterclockwise. Then he added "it's not like a Fender, you can't adjust it like a Fender". Ok, but it sounds weird I said. Then he asked how loud I set the volume and I said 3 to 5. "that's your problem" he replied. "Turn it up to 8 or more and you will have the greatest rock amp ever made". I turned it up to 9 and let it rip. There it was, the Stones guitar sound. Except it was so loud birds fell from the sky, dogs started howling for miles around, all the pictures fell off the walls in my house, planes had to be diverted from my area and the cops and fire department showed up within 15 minutes. I decided to sell it and get another one if and when my band started playing arenas.