Accuphase E-406 (1993)

Name: Accuphase E-406
Brand: Accuphase

An integrated stereo amplifier released in June 1993 with high-power output and advanced analog circuitry.

Overview

The Accuphase E-406 is an integrated stereo amplifier developed by Accuphase Laboratory, Inc., combining preamplifier and power amplifier sections in a single chassis. Released in June 1993, it was designed as a high-performance solution using technologies refined through years of separate component development. The amplifier delivers 170W per channel into 8 Ω and features discrete circuitry, balanced inputs, and a dedicated headphone amplifier. It includes a remote commander (RC-10) and supports optional input boards via two rear-panel slots compliant with the AAB interface standard.

Specifications

Production Year	June 1993
Output Power (8 Ω)	170W/ch
Output Power (4 Ω)	220W/ch
Total Harmonic Distortion	0.02% (4–16 Ω, 20 Hz–20 kHz)
Damping Factor	120 (8 Ω, 50 Hz)
Frequency Response (Main Input)	20 Hz – 20 kHz ±0.2 dB at rated output
Input Sensitivity (High Level)	147mV for rated output
Input Impedance (Balanced)	40k Ω
S/N Ratio (Main Input)	130dB (input short, A-weighted)
Power Consumption	620W at 8 Ω rated output
Dimensions	475 × 180 × 423 mm
Weight	28.0 kg
Power Supply	AC100V/117V/220V/240V, 50Hz/60Hz
Speaker Outputs	Two sets of solid brass terminals, bi-wire capable
Remote Control	RC-10, infrared pulse system, 2×R03 batteries

Design

The E-406 uses Accuphase’s original differential pure complementary push-pull circuit topology with current feedback in both line and power amplifier stages. The input stage employs a Darlington-connected, emitter-grounded differential amplifier, while the output stage features a triple parallel push-pull configuration with four parallel output devices mounted on a large heatsink. Power transistors are high-current audio-specific devices. The power supply uses separate toroidal transformers for preamp and power amp sections, including a 9 kg transformer for the amplifier, along with 33,000 μF×2 block capacitors and a local active ripple filter. Signal switching is handled by nitrogen-filled, gold-plated relays under microcomputer control. The chassis is non-magnetic and vibration-resistant, with a signature champagne/gold faceplate and large dual analog power meters with peak hold.

Context

The E-406 was developed as Accuphase’s ideal integrated amplifier, combining decades of expertise from their separate preamp and power amp designs. Accuphase was founded in late 1972 by former Kenwood engineer Jiro Kasuga, with Kenwood as a partial owner; Kenwood retained ownership interest until the mid-1990s.

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