Accuphase C-240 (1978)
Stereo control amplifier released in September 1978 with fully symmetrical Class A DC circuitry and a distinctive push-button interface.
Overview
The Accuphase C-240 is a stereo control amplifier manufactured by Accuphase Laboratory, Inc. in Japan and released in September 1978. It features a fully symmetrical push-pull Class A DC design across all amplification stages, from the head amplifier input to the headphone output. The unit is housed in a natural rosewood cabinet and features a unique front panel layout with four rotary knobs, one lever switch, and 57 push switches, offering a tactile interface with electronically controlled relay switching for input selection. It was built during the "Golden Era" of Japanese high-fidelity audio equipment.
Specifications
| Production Year | Released September 1978 |
| Frequency Response | High level input: 20 Hz – 20,000 Hz +0/-0.2 dB; Disk input: 20 Hz – 20,000 Hz ±0.2 dB |
| Harmonic Distortion | 0.005% (20 Hz – 20 kHz, rated output) |
| Power Consumption | 80W |
| Dimensions | 466 mm (W) × 188 mm (H) × 391 mm (D) |
| Weight | 18 kg |
| Power Supply | 100 V, 117 V, 220 V, 240 V, 50/60 Hz |
| Input Sensitivity / Impedance | DISC1,2 (Head Amp OFF): 2.0mV/100Ω, 47kΩ, 82kΩ, 150kΩ switching; DISC1,2 (Head Amp ON): 0.1mV/100Ω fixed; Tuner, AUX, Tape Play: 126mV/50kΩ |
| Rated Output / Impedance | Output: 2.0V/2Ω; Tape Rec1,2: 126mV/500Ω |
| Headphone Output | 0.3Ω impedance, 0.25W into 8Ω (1kHz, 0.01% distortion) |
| S/N Ratio | High level input: 110dB; Head Amp OFF: 85dB; Head Amp ON: 72dB |
| Tone Controls | 8-step push switch, ±8dB at 50Hz/20Hz (bass), ±8dB at 20kHz/50kHz (treble), 2dB steps |
| Loudness Compensation | Three settings: +6dB, +9dB, or +10dB at 50Hz (+6dB at 20kHz on COMP3, active below -30dB volume) |
| Subsonic Filter | 17 Hz, 12dB/octave |
| Semiconductors | 159 transistors, 10 FETs, 102 diodes |
Design
The C-240 uses a Class A DC system with symmetrical push-pull drive in all amplification stages, including the head, equalizer, high-level, and headphone amplifiers. The head amplifier features an input differential push-pull configuration with specially developed ring emitter transistors (RET) for small signals, while the equalizer amplifier uses FET buffers and RETs for high-frequency power amplification. The high-level amplifier employs a DC servo method (PAT, PEND). The volume control uses 18-brush sliding elements with mirror-finished conductive plastic resistors. Input selection is electronically controlled via relays, activated by feather-touch push switches, with each push switch and relay using a dual-circuit arrangement to reduce contact resistance. The PureCon headphone amplifier ensures high-fidelity output.
Market
An example unit was listed at $1,350 five years ago, described as in excellent condition with only minor aging such as scratches and coloration, and confirmed by a professional technician to be in flawless working order.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.