Vintage McIntosh MC40 // Tube Amplifier Monoblocks / Professional Electronic Restoration

The McIntosh MC40 hardly needs an introduction. With solid American engineering, and a design that embraces the principles of classic and modern aesthetics, these monoblocks are not just amplifiers; they are a timeless expression of audio excellence. This pair proudly shows some patina of time, yet sonically they perform as well as when they left the production line 60 years ago.

RESTORATIONS

• Full 30-point service check
• Replaced input jacks
• Replaced two power supply capacitors
• Tested all tubes
• Cleaned controls, switches, and internal electronics
• Exterior detailed

SPECS

Type   Monophonic vacuum tube amplifier

Power output   40 watts into 8Ω (mono)

Frequency response   20Hz to 20kHz

Total harmonic distortion   0.5%

Input sensitivity   0.5V

Signal to noise ratio   90dB

Speaker load impedance   4Ω to 16Ω

Valve complement  2x 6L6GC (output), 2x 12AX7, 1x 12AU7, 1x 12BH, Solid State Rectifier

Dimensions   13.75"W x 7.75"H x 8"D

Weight   30 lbs. ea.

LINER NOTES

The MC40 uses an advanced design of the McIntosh output transformer. The Unity Coupled^® transformer design incorporates all of the benefits of the original McIntosh design and even further improves the power bandwidth. Leakage inductance (lack of coupling) between the primary and secondary wind­ings of the output transformer limits the high frequency response of an amplifier. The primary and secondary windings of the McIntosh output transformer are interleaved five times to improve coupling. The inter­leaving is accomplished by winding groups of primary layers, then secondary layers alternately, until the total transformer is wound. Interleaving helps to extend the McIntosh power band width to over 100,000 cycles. Since 1947 his new technology has been built into every McIntosh power amplifier.