McIntosh’s first ‘Unity Coupled’ circuit was patented in 1949 and produced as the 50W-1 amplifier. Its high output power (50 watts from a pair of 6L6 tubes), wider bandwidth (20 Hz to 20,000Hz) and distortion of less than 1% were pretty impressive features for this time. Two years later the 50W-1 was replaced by the 50W-2 with similar specifications.

This amplifier was constructed on two separate chassis – one for the power supply (P50D) and the other containing the amplifier. Both units were of identical size and could be rack-mounted. The amplifier consisted of a pair of 6L6-G tubes driven by two 6J5’s with a 12AX7 doubling as phase inverter and preamplifier. For applications requiring continuous running above the rated power of 50 watts, McIntosh recommended the replacement of the 6L6-G output tubes with Tungsol 5881s.

Both the driver and output transformers were potted into a single case which also doubled as the actual amplifier chassis. Similarly, the power supply chassis was also integrated with the potted power transformer.

The 50W-2 was intended to be used with McIntosh’s C104, AE-2A or ACF-1 preamplifiers although it could accommodate any other high-quality control unit. To this end, various ‘plug-in’ components (for example, a 12AX7 preamplifier tube for use with McIntosh’s ACF-1 preamplifier or an input transformer) could be inserted into sockets provided on the amplifier chassis to maximize the versatility of the equipment.

Retailing for $249.50, the 50W-2 was produced from 1951 to 1955. Today this rare landmark amplifier typically fetches between $1000 - $1500 for good to excellent working examples.

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Photographs courtesy of Matt Hardy