Accuphase M-60 (1975)
Monoblock power amplifier introduced in July 1975 with 450W into 4Ω and 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, developed to eliminate inter-channel interference by dedicating one unit per channel. Built with high-quality components including Elna capacitors and Toshiba output transistors, the M-60 was engineered for both high-fidelity home audio and professional use in studios or public address systems. Its monophonic layout is physically asymmetrical, and the amplifier uses modular construction 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 uses a DC amplifier configuration with no capacitor in the negative feedback loop, and applies only a small amount of NFB. It features a heavy-duty power supply with a large transformer and dual 22,000 μF capacitors storing 152 joules. All amplification stages are symmetrical push-pull, and the amplifier includes a 25-contact rotary switch for 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 marked 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 from the company 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 issues include replacement of original Elna capacitors with lower-quality brands like Jack'con or Samxon, and mismatched output transistors from different manufacturers and batches, leading to failure. Some units have arrived damaged, with dented faceplates from shipping. Accuphase gear rarely requires full recapping due to robust thermal design and high-quality original parts, and owners often prefer to test capacitors rather than replace them preemptively.
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