AJ and Jack are correct, the Butler amps are definitely hybrids. A tipoff are the clearly visible internal heat-sinks for each channel, which would be for heat dissipation of their solid state output devices. Secondly, quoting from the product page: "A superlative marriage of tube and solid-state technology without the limitations of either. Literally, you get the reliable, efficient power capability of solid-state with all the greatly extended dynamics, warmth and musicality of the highest quality vacuum tube design available today."