MC275

Power amplifier, McIntosh, 1961

A stereo tube power amplifier with two 75-watt channels on one chassis, switchable to 150 watts mono, using McIntosh's Unity Coupled circuit and bifilar output transformers.

A-18, isometric, same camera for both

Drawing: A-18
Introduced: 1961
Produced: 1961 to 1971
Made in: United States
Designed by: Not credited by sources
Launch price: US$444 (first-year price listed by Radiomuseum)
Size: 438 x 203 x 311 mm
Weight: 30.6 kg

McIntosh Laboratory, founded in 1949 by Frank McIntosh and Gordon Gow, introduced the MC275 in 1961. Its owner's manual describes two 75-watt amplifiers on one chassis that can run as a stereo pair, as two independent amplifiers or as a 150-watt mono amplifier. The circuit uses four KT88 or 6550 output tubes behind three black transformer covers on a chromium chassis. McIntosh brought the amplifier back in 1993 as a Gordon Gow commemorative edition and sells a sixth generation today.

See it in listening room no. 01, at the Farnsworth House

Front elevation of the McIntosh MC275, 438 mm wide and 203 mm high — Front elevation, dimensions in millimetres. Drawn from published dimensions and descriptions; detail is simplified.

Specification

Item	As published
Power output	75 watts continuous per channel (stereo); 150 watts continuous (mono)
Harmonic distortion	Less than 0.5% at rated output, 20 to 20,000 cycles
Frequency range	+0, -0.1 dB, 16 to 40,000 cycles at rated output
Noise and hum	90 dB or more below rated output
Tubes	1 x 12AX7, 2 x 12AU7, 2 x 12BH7, 2 x 12AT7 or 12AZ7, 4 x KT88 or 6550
Input sensitivity	2.0 V (stereo input); 0.5 V (twin amp and mono inputs)
Power requirements	105 to 130 V, 50/60 cycles; 400 watts at rated output

Reissued

McIntosh MC275 (sixth generation)

McIntosh builds the MC275 again. Pricing is through dealers.

See it at mcintoshlabs.com

The house

Founded: 1949
Founder: Frank McIntosh and Gordon Gow
Origin: Silver Spring, Maryland, United States (moved to Binghamton, New York, in 1951)
Today: Owned by Bose Corporation through McIntosh Group, after Highlander Partners sold it in a deal announced on 19 November 2024.

Further sheets

Sources

Notes for the record: Production years differ: McIntosh's legacy page says 1961 to 1971, Radiomuseum 1961 to 1973, hifi-wiki 1961 to 1970. The US$444 price is Radiomuseum's first-year figure; a Stereophile column reportedly cites US$444 from a December 1963 McIntosh price list, but stereophile.com returned 403 and was not opened. No designer is listed because no source I opened credits the MC275 to a named person: McIntosh's heritage page says Frank McIntosh and Gordon Gow designed the Unity Coupled circuit and that Sidney Corderman joined in 1951 as head of research and engineering. Dimensions and weight are from the owner's manual (17 1/4 x 12 1/4 x 8 in, 67.5 lb) converted at 25.4 mm per inch and 0.4536 kg per lb; Radiomuseum lists 438 x 203 x 311 mm and 30.6 kg.