The MC901 is a monoblock amplifier that drives a single speaker. But it is unlike any other monoblock amplifier. What makes the MC901 so unique is that it's two amplifiers combined into one. Adding to the uniqueness is that each amplifier is of differing design philosophies: the MC901 consists of a 300 Watt vacuum tube amplifier attached to a 600 Watt solid state amplifier on one unified chassis. The ultimate solution for bi-amping loudspeakers: 300 Watt vacuum tube amplifier and 600 Watt solid state amplifier on one chassis Vacuum tube section powers mid and upper drivers Solid state section drives power hungry woofers DualView™ Power Output Meter Power Guard® that monitors and adjusts the input signal in the 600 Watt solid state amplifier section in real time, then makes unobtrusive adjustments to prevent harsh sounding distortion and potential speaker damaging clipping. Power Guard Screen Grid Sensor™ (SGS). The 300 Watt vacuum tube amplifier section of the MC901 breaks new ground as it's our first amplifier to feature our new Power Guard SGS™ technology. Power Guard SGS helps prevent premature vacuum tube failure by monitoring the screen grid current in the KT88 output vacuum tubes. If the current becomes too high, a circuit in Power Guard SGS is activated which then dynamically attenuates the input signal in real time to keep the vacuum tubes operating at safe levels. Sentry Monitor™ observes the output current and shuts the amplifier off if it ever exceeds safe limits. Quad Balanced design that cancels virtually all noise and distortion that may have crept into the audio signal. Power Control that can send power on/off signals to other connected McIntosh components for easy system power up and shutdown. Our patented, gold-plated Solid Cinch™ speaker binding posts that easily and securely attach the speaker cables. McIntosh Monogrammed Heatsinks™ that are connected to advanced high current output transistors efficiently cool the solid state amplifier section. Our Power Management System that will turn the entire unit off after a set amount of time when no input signal has been detected.