The Lazy J 20 is based on a late 50s Fender amp but with all available options.

It is a 2 channel, hand build, point to point wired amp, which delivers ca. 18 Watts into a 12” speaker (Celestion Alnico)
 
The 2 channels are marked Normal and Bright with a Volume control for each one. The Tone control affects both channels equally.
 
Looking at the 4 inputs from the back of the amp, the 2 on the right are for the Normal Channel and the 2 on the left are for the Bright Channel.
 
The amp is set up with a GZ34 rectifier and a pair of 6L6s in the power amp, and uses two 12AX7s.
 
The Lazy J reverb is a tube driven reverb circuit with a full size reverb tank, adding another dimension to the amp (comes with a reverb footswitch).
 
Ground knob is in fact a preamp voltage boost which will gives you more crunch/distortion without increasing volume level.
 
Artists known for using LAZY amps : Richard Ashcroft, Jeff Beck, Sam Beer, Bleech, Joe Bonamassa, Dom Brown (Duran Duran), Dylan Burns (The Bodyrockers), Bernard Butler, Mike Campbell (Tom Petty and the Heartbreakers), Eric Clapton, Nalle Colt (Vintage Trouble), Alan Darby (Eric Clapton, Bonnie Raitt, Queen, Van Morrison, etc...), Gwyn Garfield Davies, Al Duncan, Noel Gallagher, David Gilmour, Mark Griffiths (The Shadows), Gary Hooker (Brad Paisley), Neil Ivison (The Misers), Simon Johnson, Gary Kemp, Mark Knopfler, The Kooks, Robbie McIntosh, The Magic Numbers, Ray Majors, Scott McKeon, John Parricceli, Adam Phillips, P.I.L., Luke Potashnick, Razorlight, Paul Sayer, Jeremy Stacey, Paul Stacey, Pete Townshend, Joe Walsh, Paul Weller, Steve Winwood.