Accuphase C-7 (1979)

Name: Accuphase C-7
Brand: Accuphase

MC head amplifier released in April 1979 with a fixed 100 Ω input impedance optimized for a wide range of MC cartridges.

Overview

The Accuphase C-7 MC Head Amplifier was released in April 1979 by Accuphase Laboratory, Inc. as a dedicated head amplifier for moving coil (MC) cartridges. It was designed to directly reproduce the original character of MC cartridges, with all stages using push-pull DC configuration and a modular construction sealed in epoxy resin. The unit features a PASS switch that allows direct input-to-output connection for use with non-MC cartridges.

Specifications

Gain	26dB
Frequency response	5 Hz ~ 100 kHz +0, -0.2 dB
Max Input	35 mVrms (20 Hz to 20 kHz, 0.002% distortion)
Harmonic distortion	0.002% (20 Hz to 20 kHz at maximum input)
S/N ratio (IHF-A, RIAA applied)	72 dB (0.1 mV input)
Input conversion noise (IHF-A, RIAA applied)	-152dBV
Input impedance	100 Ω
Output impedance	100 Ω
Semiconductor count	Transistor: 26, FET: 9, IC: 2, Diode: 8
Power supply voltage	AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption	5W
Dimensions (W x H x D)	102 x 61 x 350 mm
Weight	2.5kg
Original price	¥70,000 (April 1979)

Design

The C-7 uses a differential push-pull input stage with four RETs (Ring Emitter Transistors), a type developed specifically for signal amplification by Accuphase. The ICL method eliminates the input capacitor through perfect balance in the differential circuit. The main circuit is modular, with the printed board sealed in epoxy resin. Each channel has its own dedicated constant-voltage power supply located adjacent to the amplifier module. The unit contains one power transformer, two amplifier modules, and a relay.

Context

The C-7 was developed to directly convey the individuality of MC cartridges, with its 100 Ω input impedance chosen after auditioning various models—from low-impedance types like 2–3 Ω Orthophone to high-impedance 40 Ω EMT cartridges. Its circuit design is derived from the head amplifier sections of the Accuphase C-220 and C-240. Kensonic, the parent company of Accuphase, first launched the P-300 amplifier, C-200 preamp, and T-100 tuner as its initial products.

Market

The Accuphase C-7 was originally priced at ¥70,000 at its April 1979 release. User reports indicate that when functioning properly, volume must be "cranked past 12 oclock" when used with an Accuphase AC-1 MC cartridge.

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