The Peavey 5150 is the guitar amp endorsed and used by Eddie Van Halen.
It is a very high gain amplifier with five 12AX7's in the preamp stage and the early models had coveted and rare Sylvania 6L6 tubes in the power amp section. Earlier models had "EVH" in block letters on the front, while later models have a facsimile of Eddie's signature. The ones with the block letters are generally more sought after by those in the know.
Originally this amp was only available as a full or half stack, but now there is a 2x12 combo amp available as well. The combo amp features built in reverb.
There is also a "Peavey 5150 II" (which I have not seen) which features separate EQ controls for the lead and rythym channels.
There are two inputs, a "high gain" and "normal".
There is a "crunch" button, which essentially makes the rythym channel into a second lead channel, but with not quite so much gain as the real lead channel. There is a "bright" button that boosts the treble frequencies in the rythym channel.
There are "pre gain" knobs for the rythym and lead channels, these control the amount of distortion introduced.
There are "low", "mid", and "high" EQ knobs that are shared by the rythym and lead channels.
There is a separate "post gain" knob for each channel which acts as a master volume control.
There is a "presence" knob which boosts high frequencies to make the sound "cut" through the mix.
There is a "resonance" knob that boosts the signal at the resonant frequence of the 5150 4x12 speaker cabinet.
Finally there are "power" and "standby" switches.
This amp is a lot of fun to play with, it has unbelievable amounts of gain. On the lead channel any "pre gain" setting past about "7" is just ridiculous.