McIntosh mr78 (1972)

Name: McIntosh mr78
Brand: McIntosh

A high-performance FM tuner with Phase Locked Loop demodulation and exceptional selectivity for its era.

Overview

The McIntosh MR78 is an FM tuner introduced in 1972 as the flagship model in McIntosh's tuner lineup. Designed for serious FM listeners, it delivers outstanding sensitivity and selectivity, with performance that remains competitive with modern tuners. It features a four-gang tuning capacitor and a crystal filter in the IF stage, contributing to its excellent signal rejection and stable reception.

Specifications

Power consumption	60 watts
Dimensions (W x H x D)	16" x 5-7/16" x 12" (406mm x 138mm x 305mm)
Weight	27 lbs (12.2 kg)
Frequency response	20Hz to 20kHz
THD (mono)	0.15%
THD (stereo)	0.3%
Capture ratio	1.0dB
Selectivity	90dB
Signal-to-noise ratio (mono)	80dB
Signal-to-noise ratio (stereo)	70dB
Stereo separation	40dB at 1kHz
Alternate frequency	Yes
Tuning meter	Signal strength and center of channel
Muting	Adjustable
Outputs	Fixed and variable
Output level (variable)	2.5 volts
Output impedance	4700 ohms
Power requirements	100, 120, 220, 240 volts, 50/60 Hz
Sensitivity (IHF)	1.8µV
Sensitivity (50dB quieting, mono)	2.5µV
Sensitivity (50dB quieting, stereo)	25µV
AM suppression	65dB
Image rejection	100dB
IF rejection	100dB

Design

The MR78 was McIntosh's first tuner to use a Phase Locked Loop (PLL) multiplex demodulator circuit. It also featured a four-gang tuning capacitor and a crystal filter in the IF stage for excellent selectivity.

Context

The MR78 was introduced in 1972 as McIntosh's top-of-the-line FM tuner and served as the flagship model in their tuner lineup during the early 1970s.

Market

The MR78 remains highly sought after by vintage audio enthusiasts and can command high prices on the used market. Common issues include failing capacitors in the power supply and multiplex sections, which should be replaced to restore original performance. The tuning meter bulbs often burn out and need replacement. The four-gang tuning capacitor is generally reliable but can become noisy or develop poor contact; cleaning with a specialized contact cleaner is recommended.