Now here’s an amp that covers a lot of ground from pristine cleans to creamy thick overdrive tones, the OS21 RT is Mad Professor’s 21 Watt amp powered by 4 12AX7 preamp tubes and 2 6V6 power tubes now with built in Reverb and Tremolo hence the addition of RT to the name. The Old School 21RT comes in either a head or a 1×12″ Combo and is a single channel amplifier designed to be reactive to your guitar volume. The amp is also designed to take pedals well, you would hope it would coming from a pedal manufacturer! To hear all of the tones you can get from this versatile low watter check out yet another great demo by Marko Karhu.