Accuphase C-7 (1979)
MC head amplifier released in April 1979 with a fixed 100 Ω input impedance, chosen to suit a wide range of MC cartridges.
Overview
Accuphase Laboratory, Inc. released the C-7 MC Head Amplifier in April 1979. It is a dedicated head amplifier for moving coil (MC) cartridges, designed to reproduce the original character of the cartridge directly. All stages are push-pull DC, and the construction is modular, sealed in epoxy resin. A PASS switch connects input straight to output, so the unit can be used 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). Accuphase developed this type specifically for signal amplification. The ICL method drops the input capacitor by relying on perfect balance in the differential circuit. The main circuit is modular, with the printed board sealed in epoxy resin. Each channel has its own constant-voltage power supply, sitting next to the amplifier module. Inside are one power transformer, two amplifier modules and a relay.
Context
The C-7 was built to pass along the individuality of MC cartridges directly. The 100 Ω input impedance was chosen after auditioning various models, from low-impedance types like the 2-3 Ω Orthophone to the high-impedance 40 Ω EMT cartridges. The circuit design comes 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 priced at ¥70,000 when it came out in April 1979. User reports say that with an Accuphase AC-1 MC cartridge, a properly working unit still needs the volume "cranked past 12 oclock."
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