Back in 1970 the MC-275, 75 watts/channel, sold for 444 and the MC-250, 50 watts/channel, was 379 (the MC-2505 sold for 449. Terry DeWick restored my MC-250 to specs last year. Balanced Input 3 (1 Solid State, 1 Vacuum Tube, 1 Composite) One month ago I purchased a McIntosh MC-275 Mk IV to replace my MC-250 for two-channel and home theater listening.Vacuum Tube section: Unity Coupled Output Transformer Output Type Solid State section: AutoformerР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє.Circuit Design Solid State and Vacuum Tube.Circuit Configuration Solid State section: Quad Balanced.Speaker Binding Post Type Patented Solid CinchР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє Speaker Binding Posts.Frequency Response Solid State section:.Rated Power Band Solid State section: 20Hz to 20kHz.Damping Factor Solid State section: >40.Dynamic Headroom Solid State section: 2.5dB.S/N below rated output Solid State section: 122dB.Vacuum Tube section: 0.5% maximum harmonic distortion at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz Total Harmonic Distortion Solid State section: 0.005% maximum harmonic distortion at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz.Vacuum Tube section: 300 Watts 2, 4 or 8 Ohms Power Output per Channel Solid State section: 600 Watts 2, 4 or 8 Ohms.Our Power Management System that will turn the entire unit off after a set amount of time when no input signal has been detected.McIntosh Monogrammed HeatsinksР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє that are connected to advanced high current output transistors efficiently cool the solid state amplifier section.Our patented, gold-plated Solid CinchР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє speaker binding posts that easily and securely attach the speaker cables.Power Control that can send power on/off signals to other connected McIntosh components for easy system power up and shutdown.Quad Balanced design that cancels virtually all noise and distortion that may have crept into the audio signal.Sentry MonitorР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє observes the output current and shuts the amplifier off if it ever exceeds safe limits.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. Power Guard SGS helps prevent premature vacuum tube failure by monitoring the screen grid current in the KT88 output vacuum tubes. 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 SGSР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє technology. Power Guard Screen Grid SensorР В Р вЂ Р Р†Р вЂљРЎвЂєР РЋРЎвЂє (SGS).Power Guard Р В РІР‚в„ўР вЂ™Р’В® 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.While an entirely new design, the MC901 comes with the technology one would expect from a McIntosh amplifier:

Mcintosh mc 250 vs 2100