Accuphase M-60 (1975)
Monoblock power amplifier introduced in July 1975 with 450W into 4Ω. It had a reputation for driving demanding speakers with clarity and control.
Overview
The Accuphase M-60 is a monaural solid-state power amplifier released in July 1975 as the flagship of Accuphase's lineup. It was the company's first monoblock design. One unit per channel was meant to eliminate inter-channel interference. It uses Elna capacitors and Toshiba output transistors, and it was built for high-fidelity home audio as well as professional use in studios or public address systems. The monophonic layout is physically asymmetrical, and the amp is modular, with all stages in symmetrical push-pull configuration.
Specifications
| Rated Output | 450W (4 Ω), 300W (8 Ω), 150W (16 Ω) |
| THD | 0.03% or less (rated output), 0.01% or less (-3dB output) |
| Frequency Response | 20Hz–20kHz (+0, -0.2dB, 8Ω); 2Hz–150kHz (+0, -3.0dB, 1W) |
| Damping Factor | 120 (at 40Hz, 8Ω) |
| Input Sensitivity / Impedance | 2.0V / 100k Ω |
| S/N Ratio (IHF-A) | 115 dB (at rated output) |
| Power Consumption | 65W (idle); 800W (4Ω rated); 540W (8Ω rated) |
| Dimensions | 482 x 170 x 345 mm (19" rack) |
| Weight | 27 kg |
| Output Meter | Logarithmic, -50dB to +3dB, Peak/Level switch |
| Attenuator | Precision 1 dB steps to -20dB, then -23dB, -26dB, -30dB, -∞ |
| Subsonic Filter | 17 Hz, 18dB/octave |
| Semiconductors | 47 Transistors, 3 ICs, 51 Diodes |
| Power Supply | AC 100/117/220/240V, 50/60Hz |
| Rise Time | 3 μSec |
| Slewing Rate | 25 V/μSec |
Design
The M-60 is a DC amplifier with no capacitor in the negative feedback loop, and it applies only a small amount of NFB. The power supply is heavy-duty, with a large transformer and dual 22,000 μF capacitors storing 152 joules. All amplification stages are symmetrical push-pull. A 25-contact rotary switch gives precise 1 dB attenuation. A Canon (XLR) input supports professional applications, and a separately sold forced-air cooling fan (O-81) can be installed. The unit is 19-inch rack-mountable with a 100 mm pitch.
Context
The M-60 was the first monoblock amplifier from Accuphase and the top of the company's range at its launch in 1975. It followed early products like the P-300 amplifier, C-200 preamplifier, and T-100 tuner. The company was founded in late 1972 by former Kenwood engineer Jiro Kasuga.
Market
A restored unit was listed for RM 14,000 in 2023, and a recent restoration cost $3,000. Common problems include original Elna capacitors replaced with lower-quality brands like Jack'con or Samxon, and mismatched output transistors from different manufacturers and batches, which lead to failure. Some units have arrived with dented faceplates from shipping. Accuphase gear rarely needs a full recap because of its thermal design and high-quality original parts, and owners often test the capacitors rather than replace them preemptively.
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