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. Designed to correct transmission characteristics, it uses 33 bands based on ISO standard center frequencies to flatten sound field response. It features discrete amplifiers built from 706 transistors, 8 FETs, 10 ICs, and 129 diodes, avoiding IC operational amplifiers for signal purity. The unit includes both unbalanced RCA and balanced XLR input/output connections, with balanced input impedance switchable between 600 Ω and 40k Ω. It is intended to be inserted between a preamplifier and power amplifier, with no tape loop or 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 where filter sharpness remains unchanged regardless of boost or cut level. Each bandpass filter consists of two buffer amplifiers and 33 dedicated amplifiers, all using discrete transistor and FET designs without 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, and the chassis uses separate left and right signal paths to prevent crosstalk. Ventilated steel top and bottom panels aid cooling, and the front is protected by a smoked acrylic cover. The front panel comes in champagne gold or black (G-18B). Two unswitched rear AC outlets 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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