From the manufacturer's website:

The TRI-O.D. can be used with any amp/combo, or to drive a power amp and guitar speaker cabinets. While designed primarily for live performances, you can also record direct with each of the prevoiced tube amp sounds.

One footswitch takes you through three completely different tube amp characters. When you change channels, there is a distinct difference in the entire sound, not just the gain structure and EQ.

Each independent channel has its own Drive and Level controls, which allows you to set them relative to each other. The Master Output Section’s Volume control can then be set for the particular occasion – songwriting at sunrise or grinding at the local Grunge-O-Rama.

Because each channel can be turned off, you can designate how many you want to switch between: all 3, 2, just 1, or even none. Turning off all 3 channels enables you to use the Speaker Simulator and Master Output Section only. This feature is useful when you want to record direct using any other pre-amp, fuzz box, or effect unit in your collection.

True channel switching with a single footswitch is another Tech 21 innovation. The custom footswitch actuator provides a smooth transition between channels for instantaneous switching. Though deceiving in design, you’re never more than two stomps away from the sound you want.

Operable with optional DC power supply,, or 9V alkaline battery (not included).

Actual size: 4.5″ x 3.5″ x 1.5″ / Weight 14 oz.