After my great experience with the JCM900 SL-X head, I knew the next on my list would be the Mk III in some form. I spotted this one online for a great price and had to have it, despite the combo form factor growing increasingly less appetizing for me (my music room is starting to get very tight on space!).
This one dates from 1990, is equipped with EL34 tubes, and is essentially the 50w Model 2500 head in a short chassis mounted into a small combo amp. It also comes equipped with one of my all time favorite speakers, the Celestion G12H-100 from the same year. Despite its compact size, it is fairly heavy and kind of cool for a combo amp, comes equipped with inset side handles much like the Marshall 1960 cabinets do, so moving this amp around is a breeze. Really, it’s the ultimate single channel “jam” amp and couple with a 2x12 or 4x12 speaker cab could likely cover just about any gig (the larger speaker cab only needed to fill out lower frequencies in the room, the 1x12 gets plenty loud on its own!)
Much like the SL-X, this was the continuation of the single channel Super Lead Mk II amps of the 70s and 80s. It has a single channel, but two footswitchable master volume controls and a second gain control - in this case controlling the amount of clipping diode distortion added in the preamp. The nice thing about the Mk III is that you can turn this extra gain completely off by rolling the knob down to zero, essentially lowering the voltage passing through the clipping circuit so the diodes never reach minimum voltage to activate. This gets you the classic 3-stage gain structure of your favorite 2203/2204 JMP’s and JCM800s. While the overall circuit does have some differences, this is very authentic sounding and can nail those classic tones as well as a few new ones with the additional controls and effects loop.
