McIntosh 10B (circa 1957–1959)

Name: McIntosh 10B
Brand: McIntosh

Seventeen tubes, a gold anodized face, and a wood cabinet. It is an FM-only tuner, and a serious one.

Overview

The McIntosh 10B weighs thirty-two pounds. It has a wood cabinet and an anodized gold front panel. It is an FM-only, tube-type tuner, built at the very start of the stereo FM era. Sources date delivery to 1957/1958, though other documentation suggests 1958/1959. Either way, it was built before anyone had settled how stereo broadcasting would work.

The naming is a mess. Some documentation calls this unit the "MR10B" or "MXR10B," while the Vintage Audio Catalog simply calls it the "McIntosh 10B FM Stereo Tuner." The specs below come from sources that use these names somewhat interchangeably. If you see "MR10B" in a service manual or catalog listing, it is almost certainly the same chassis. This page uses 10B.

What makes the 10B genuinely remarkable — beyond the obvious build quality — is what it does with an FM signal. The frequency response stretches from 20 Hz to 20 kHz within ±0.5 dB, which was exceptional for the period and remains respectable by any standard. Total harmonic distortion is rated at 0.1%, a figure that tube tuners of the era rarely approached. This wasn't a casual table radio with pretensions; this was McIntosh applying its amplifier philosophy to the tuner problem, and the results show.

Key Features

Seventeen Valves and a Silicon Diode Power Supply

Radiomuseum.org documents seventeen valves in the 10B's signal path and control circuitry. The power supply uses a silicon diode rectifier rather than the tube rectifiers found in earlier designs, which was forward-thinking for the late 1950s. That cut heat and voltage sag under load, which helps the tuner's stability. The unit runs on 117 V AC.

Each stage - RF amplification, local oscillator, mixer, IF amplification, ratio detector, and the multiplex decoder - gets dedicated attention instead of sharing duties with another. That is the McIntosh approach: throw engineering at the problem until it gives up.

Four-Gang Tuning with Six Circuits

The front end uses four varying capacitors across six tuning circuits. More tuning circuits mean better image rejection and better selectivity, which helps when you're separating adjacent stations in a crowded band. Selectivity is rated at 60 dB, so the 10B can hold the station you want while rejecting the one next door, even when the signal strengths are very different. Sensitivity is rated at 1.5 µV for 30 dB quieting, so weak, distant stations come through with little background hiss.

Balanced Outputs and Flexible Connectivity

The 10B has both fixed and variable audio outputs. The fixed output feeds a preamplifier at a consistent level, while the variable output allows direct connection to a power amplifier with volume handled at the tuner. Audio output level is 2.5 V with an output impedance greater than 1000 ohms, enough to drive long interconnect runs without degradation. Antenna inputs take both 300 ohm twin-lead and 75 ohm coaxial cable. Channel separation is rated at 50 dB at 1 kHz, which for the late 1950s was impressive. Early stereo FM decoders often struggled to reach half that figure.

The signal-to-noise ratio is 70 dB, so in quiet passages the tuner's own noise floor stays well below the music. This is where tube tuners of the period typically fell apart, hissing and humming through broadcasts. The 10B's clean power supply and careful circuit layout keep that noise in check.

External Power Supply Design

John F. Rider's "Inside the Tuner" notes the 10B's construction as a tube-type, FM-only tuner with an external power supply. Keeping the power transformer and rectifier circuitry out of the main chassis reduced both heat and magnetic interference in the sensitive RF and audio stages. The tuner section stays cooler, which extends component life and reduces frequency drift as the unit warms up. It also lets the main chassis be more compact, though at 16 inches wide, 5 1/4 inches high, and 12 inches deep, the 10B is still a big piece of equipment that needs real shelf space. It weighs 32 pounds.

Physical Design and Finish

The wood cabinet and anodized gold front panel give the 10B a visual presence that matches its technical ambitions. The anodizing holds up well over decades when cared for properly, though examples with wear show their age more visibly than painted finishes might. The wood cabinet is typical of late-1950s McIntosh: solid, straightforward, and designed to protect the chassis while looking appropriate in a living room setting.

Collectors pursuing the 10B should note the model designation confusion appears in period documentation as well. Some sources reference the MR10B or MXR10B, and parts listings may appear under any of these names. When searching for service documentation or spare parts, it's worth checking all three designations. The chassis itself is the same; only the catalog naming varies.

Performance in Context

Audio magazine's May 1977 issue includes a reader letter describing work on the tuner model that would become the MR-77 during the winter of 1968-69. The writer recalls that "stereo IM distortion was the bane of all FM tuners at that time." The 10B's designers had been attacking that problem a full decade earlier, with the 0.1% THD rating and the 50 dB separation figure.

The 10B appeared on the used market in classified advertisements through the 1980s. An Audio (May 1986, p.140) classified listing shows a "108" - presumably a typo for the 10B - offered at $700 alongside McIntosh MC-75s at $7,000 the pair. That suggests the 10B was already being treated as a collectible rather than merely used gear, even as solid-state designs superseded its technology.

The fundamental design is sound, and a properly restored 10B delivers FM performance that rivals many contemporary tuners. The external power supply simplifies restoration somewhat, as the main chassis is easier to work on without the transformer weight and heat.

The 10B is not a tuner for someone seeking casual background listening. It demands a proper antenna, a quality preamplifier, and speakers that can reveal what it delivers. In return, it offers a window into late-1950s American audio engineering at its most ambitious — a time when McIntosh was willing to build a seventeen-tube FM tuner with a gold faceplate and let the specifications speak for themselves. The 10B speaks fluently, and collectors who listen carefully will hear exactly what the company was saying.