These amps are beginning to become quite sought after, as they don't come up for sale often, and feature a very unique combination of features. Essentially, what the J-20 offers is a 5E3 Tweed Deluxe format, with a full reverb circuit added, and 6L6 power tubes. There are other small circuit modifications as well, which you can find more info on the manufacturers site. This particular model does feature the Variable Attenuation Control (Master Volume), which sits where the typical ground switch would on the far left side of the chassis.