Accuphase G-18 (1985)
Third-octave graphic equalizer released in March 1985 with 33 bands, constant Q of 4.3, and discrete transistor-FET circuitry.
Overview
The Accuphase G-18 is a high-end third-octave graphic equalizer, released in March 1985. It corrects transmission characteristics, using 33 bands on ISO standard center frequencies to flatten the response of the sound field. The amplifiers are discrete, built from 706 transistors, 8 FETs, 10 ICs, and 129 diodes. There are no IC operational amplifiers in the signal path, for signal purity. Connections are unbalanced RCA and balanced XLR, both input and output. Balanced input impedance switches between 600 Ω and 40k Ω. The G-18 goes between a preamplifier and a power amplifier. It has no tape loop and no additional signal routing.
Specifications
| Format | 1/3 octave 33 band type |
| Center Frequencies | 16 Hz to 25 kHz (33 bands) |
| Q (Peak Sharpness) | 4.3 Constant |
| Band Level Range | -12.0 dB to +12.0 dB |
| Frequency Response | 0.3 Hz ~ 160 kHz (+0, -3.0 dB); 1.0 Hz ~ 40 kHz (+0, -0.2 dB) |
| Gain | 0 dB (band level control: 0 dB) |
| THD | 0.002% (EIA 16Hz–25kHz) |
| S/N Ratio (EIA) | 110 dB |
| Input Impedance | Unbalanced: 20k Ω; Balanced: 40k Ω / 600 Ω switching |
| Output Impedance | Unbalanced: 10 Ω; Balanced: 50 Ω |
| Load Impedance | Unbalanced: 1k Ω or higher; Balanced: 600 Ω or higher |
| Max Input/Output | 8 vrms, +20dBm/600Ω (balanced, control at 0 dB) |
| Power Supply | AC100V/117V/220V/240V, 50Hz/60Hz |
| Power Consumption | 55W |
| Dimensions (w/o cabinet) | 445 × 160 × 373 mm |
| Dimensions (with A-8 cabinet) | 466 × 190 × 385 mm |
| Weight | 12.0 kg |
| Original Price | ¥330,000 / $5,450.00 |
Design
The G-18 uses a constant Q system, so filter sharpness stays the same regardless of boost or cut level. Each bandpass filter consists of two buffer amplifiers and 33 dedicated amplifiers. All of them are discrete transistor and FET designs, with no IC op-amps. The input stage uses FETs in a differential complementary push-pull configuration. The power supply has independent left and right windings with a dedicated filter circuit. The chassis keeps the left and right signal paths separate to prevent crosstalk. The steel top and bottom panels are ventilated for cooling, and a smoked acrylic cover protects the front. The front panel comes in champagne gold or black (G-18B). Two unswitched AC outlets on the rear provide up to 200 watts for other components.
Market
The Accuphase G-18 sold with an optional wood cabinet (A-8, ¥16,000). In 2025-2026, units listed for $2,046 on HifiShark and $1,800 on US Audio Mart. A product brochure sold for €6 on Kleinanzeigen in January 2026.
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Service Manuals, Schematics & Catalogs
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