VOX AD30VT Valvetronix Guitar Amplifier

How Vox's Valve Reactor Circuit works:

VOX Valve Reactor For True Tube Power
The  AD30VT features the VOX Valve Reactor found on all Valvetronix products. The Valve Reactor circuit uses a 12AX7 triode vacuum valve together with an actual low-wattage valve power amp circuit, a virtual output transformer and a dummy speaker circuit that simulates the impedance changes of a real speaker. It also reconfigures itself so that its characteristics are the same as the amps it's modeling (class A, class AB, negative feedback circuit, etc.) This means that all of the nuances of the original amp model including sound, feel, distortion and presence are reproduced accurately with the VOX AD30VT.

What is so special about a valve's sound compared to a transistor's? Overdrive a transistor amp, and it sounds shrill and brittle like breaking glass. Overdrive a valve amp, and it sounds fuller and louder. The reason is when clipped (overdriven) a valve adds lots of even order harmonics to the signal, which our ears find pleasant. Cipping a transistor amp adds both odd and even harmonics. Our ears dislike the odd harmonics as they are not harmonically related to the fundamental tone. Valves just sound better!