Усилители мощности моно — McIntosh MC901

The McIntosh MC901 is a single-channel hybrid power amplifier that places a solid state amplifier and a vacuum tube amplifier on one chassis, an arrangement McIntosh names Hybrid Drive. Combined output reaches 900 W per unit. McIntosh put the unit on its list of retired models, still offered while stock lasts, and its launch price was USD 22,000 per unit. Its success led the company to develop the more compact MC451.

Key specs that matter

The transistor section is rated at 600 W and the valve section at 300 W, each into 2, 4 or 8 ohms. Maximum distortion from 20 Hz to 20 kHz is 0.005% on the solid state side and 0.5% on the tube side. Signal-to-noise ratios are 122 dB and 112 dB below rated output. The solid state amplifier spans 10 Hz to 100 kHz at -3 dB, while the tube amplifier reaches 10 Hz to 70 kHz. Dynamic headroom is 2.5 dB and 1.2 dB, and damping factor exceeds 40 and 18 for the two halves. The enclosure is about 445 mm wide, 340 mm high and 750 mm deep, with a weight of 81.6 kg, or 90.7 kg packed.

Engineering and use context

The valve half runs eight KT88 output tubes together with four 12AT7 and two 12AX7A signal tubes. Three balanced XLR inputs are provided - one reaches only the solid state section, one only the tube section, and a third composite input feeds both at once. Output connections use patented Solid Cinch binding posts with separate taps for 2, 4 and 8 ohm loads. A DualView power output meter on the front carries an independent mechanical meter for each amplifier section, so the load on the transistor and valve stages can be watched separately. The tube section introduced Power Guard SGS, which monitors screen grid current in the KT88 tubes and, if it rises too far, attenuates the input signal in real time to keep the tubes at safe levels and prevent premature failure. The built-in low pass filter knob offers settings including 100 Hz and 1 kHz for dividing the range between the two sections.

Pairing

The split design targets loudspeakers with separate bass and treble terminals, where the stronger transistor stage can take the woofers and the tube stage the upper range. A stereo setup needs a pair of units, and the all-XLR input panel requires a preamplifier with balanced outputs. The composite input lets a single balanced cable drive both halves when a preamplifier offers only one balanced output per channel.

Alternatives

The McIntosh MC451 is the smaller hybrid monoblock of the same concept, combining a solid state section with a valve section that uses four KT88 tubes.