McIntosh MC2120 Speakers (1980-1985) — Specs & History

Stereo power amplifier with Power Guard protection and output transformer-coupled design

Overview

The McIntosh MC2120 is a solid-state stereo power amplifier produced during McIntosh's classic solid-state era. It delivers 120 watts per channel into 8 ohms with exceptionally low distortion across the full audio band. Designed for both performance and speaker protection, it features the proprietary Power Guard system and output transformers that ensure consistent power delivery across all load impedances.

Specifications

Rated output stereo	120W+120W
Rated output mono	240W
Output load impedance	Stereo: 2Ω, 4Ω, 8Ω, 16Ω; Mono: 1Ω, 2Ω, 4Ω, 8Ω
Frequency response	20 Hz ~ 20 kHz +0 -0.25 dB (at 1W)
Total harmonic distortion	0.1% or less (0.25W–120W, 20Hz–20kHz)
Signal-to-noise ratio	95 dB or more (at rated output)
Input Sensitivity / Impedance	0.75 V, 2.5 V (switching type) / 100k Ω
Power consumption	50W (no signal); 460W (max output)
External dimensions	Body: 372W × 127H × 330D mm; Front Panel: 407W × 132H mm
Weight	25.9 kg (net); 31.8 kg (packed)
Power supply voltage	120 VAC, 50Hz/60Hz
Semiconductors used	39 silicon transistors, 2 ICs, 24 silicon diodes

Design

The MC2120 features a Power Guard system that compares input and output waveforms, lighting a warning lamp at 0.5% difference and activating protection at 1% to prevent clipping and speaker damage. The amplifier uses a monolithic transistor differential input stage for low noise, followed by a class A voltage amplifier. The driver and complementary service circuits operate near class A to minimize crossover distortion, while the power transistors run in class AB. The output stage is a single-ended para-push type using six complementary power transistors. Output is transformer-coupled, allowing full power delivery into any load impedance and providing protection in case of amplifier failure.

Context

The MC2120 is part of McIntosh's "Classic Models" lineup from the solid-state era, representing the brand's commitment to high-fidelity performance and robust engineering.