Accuphase E-303X (1983–1987)
Accuphase took its 1978 E-303 back to the drafting table, tripled the output stage, and built an integrated amp meant to survive the CD era.
Overview
Twenty and a half kilograms of amplifier, and it still only stands 160 millimeters tall including the legs. That ratio tells you most of what you need to know about the Accuphase E-303X: a wide, shallow, densely packed chassis — 445 by 160 by 370 millimeters — with almost no air inside it. Accuphase released the E-303X in December 1983 at ¥298,000, and the company's own literature framed it as a "new generation integrated stereo amplifier with consideration for the playback of digital sources such as PCM and CD," built on technology and materials cultivated in Accuphase's separate preamplifier and power amplifier lines.
A 1983 integrated amp that names Compact Disc as a design consideration was reading the room correctly. The E-303X was rated at 150 watts per channel into 8 ohms, 200 watts per channel into 4 ohms, and 75 watts per channel into 16 ohms. All of that is under EIA continuous average power conditions, both channels driven from 20 Hz to 20 kHz at no more than 0.01% distortion (HiFI-Stereo, 1986, p.59). It was also rated down to a 2-ohm load. Accuphase's documentation explains why: nominal speaker impedance is measured at one frequency, and real speakers dip well below their badge rating. The E-303X was built to absorb those dips rather than trip a protection circuit.
American buyers got it through Madrigal Audio Laboratories, which distributed Accuphase in the United States. The 1986 HiFI-Stereo equipment directory listed the E-303X at 150 watts per channel with MM phono, tape, AUX, and CD player inputs. It gave MM phono sensitivity as 2 mV for 0.5 V output at 1 kHz, a subsonic filter rolling off at 12 dB per octave below 10 Hz, and hum-and-noise figures of 65 dB (MC), 75 dB (MM), and 100 dB (line). The same directory confirmed the Madrigal connection. Three years later, the 1989 edition still listed the E-303X with its 150 W/ch rating, its prominent front-panel power meters, and a three-position loudness compensation circuit (HiFI-Stereo, 1989, p.78).
The timeline is not clean. audio-database.com gives a release date of December 1983, and thevintageknob.org dates production from December 1983 to December 1987. A separate source has described the model as spanning roughly 1986 to 1989. The Archive treats the 1983-1987 window as the more credible one, because it lines up with the original release documentation and with the 1986 directory treating the amp as current rather than new. Collectors comparing notes should know the discrepancy exists.
Documentation is thin. No original manual, service literature, or factory spec sheet appears to have survived in the usual collector channels, and no full bench test from Audio, Stereo Review, or High Fidelity has surfaced. Most of what follows comes from Accuphase's own product documentation and the two HiFI-Stereo directory entries. If you own original literature, the Archive would welcome a scan.
Key Features
Triple Push-Pull MOS FET Output Stage
The output stage uses six power MOS FETs in a triple push-pull configuration. Accuphase's documentation notes the devices carry a maximum drain loss rating of 600W, which is the headroom that lets the amplifier deliver 200 watts per channel into 4 ohms and 75 into 16 without changing character. This was the central revision over the 1978 E-303. The original used two TO-3 pairs per channel, and the E-303X tripled the push-pull array. The rating is 150 W/ch into 8 ohms at 0.01% THD, with an IM strain rate of 0.005%.
Ahead of the output devices, the power amplifier section runs a differential push-pull input stage, a cascode push-pull second stage, and a pre-drive built around MOS FETs. Cascode is a technique borrowed from tuner front ends. It avoids the Miller effect at high frequencies, which is why the E-303X can claim a main-amp frequency response of 1.5 Hz to 150 kHz within +0/−3.0 dB at one watt. Damping factor is rated at 150 into an 8-ohm load at 50 Hz.
Direct-Coupled Signal Path with DC Servo
Accuphase wired the MC head amplifier, equalizer amplifier, high-level amplifier, and power amplifier directly together, with no coupling capacitors between stages. That removes a layer of coloration. It also invites DC drift, the classic failure mode of capacitorless designs. Accuphase's answer was a DC servo stabilizing each amplifier block. The E-303X's own literature credits the servo with solving the drift problem completely.
Full-Scale MC Head Amplifier with Three-Step Loading
Most integrated amplifiers of the era treated moving coil cartridges as an afterthought. The E-303X gives the MC input its own dedicated flat amplifier ahead of the EQ stage. The MC signal enters without passing through a capacitor, runs through carefully selected low-noise elements, and sees a low-impedance negative feedback loop to keep noise generation in check. Accuphase also shielded the constant-voltage power supply elements for the head amp, on the theory that even power-supply noise would degrade the signal-to-noise ratio of a moving coil signal.
Input impedance for MC cartridges switches across three positions: 10, 30, and 100 ohms. Sensitivity is rated at 0.085 mV for rated output, and maximum input at 1 kHz and 0.005% distortion is 9.5 mVrms with the head amp engaged. Gain from the DISC input through the tape record output is 66 dB with the head amp on. For moving magnet cartridges, sensitivity is 2.7 mV into 47k ohms with the head amp off, and maximum input is 300 mVrms.
Equalizer Amplifier: Differential FET Input, Cascode, Darlington
The phono EQ stage uses an FET-buffered differential input, a cascode pre-drive, and a Darlington-pair output, every stage push-pull. Accuphase's reasoning is that the EQ amplifier determines RIAA accuracy, so it gets the same circuit care as the power stage. The Darlington output raises the input impedance of that stage by the static forward current transfer ratio of the driver transistors, which keeps the pre-drive from being loaded down by what follows. Constant-voltage power supplies sit on each printed circuit board to reinforce the arrangement.
Logically Switched Signal Routing
Input terminals connect directly to the circuit board, and relays sit as close as possible to that board so the signal takes the shortest possible path. A logic circuit commands the relays. Accuphase specified crossbar twin-type relays with gold-plated silver-palladium contacts, hermetically sealed against the outside air. These are small-signal relays developed specifically for audio rather than lifted from industrial catalog stock.
Switch-Type Tone Controls and Three-Position Loudness
Tone adjustment is switch-based rather than continuous, which makes repeatable curves possible. Bass turnover selects between 200 Hz and 500 Hz. Treble turnover selects between 2 kHz and 7 kHz. Each band offers ±7.5 dB of range in 1.5 dB discrete steps, measured at 100 Hz for the 500 Hz bass setting, 50 Hz for the 200 Hz bass setting, 10 kHz for the 2 kHz treble setting, and 50 kHz for the 7 kHz treble setting.
The loudness compensator offers three curves rather than a single fixed boost, selected to suit room acoustics, speaker characteristics, and taste. At a volume setting of −30 dB, Comp 1 adds 3 dB at 100 Hz, Comp 2 adds 6 dB at 100 Hz, and Comp 3 adds 8 dB at 100 Hz plus 6 dB at 20 kHz. A separate −20 dB attenuator drops the volume without disturbing the volume control's position.
Logarithmic Peak-Reading Power Meters
The front-panel meters use logarithmic compression with peak hold, reading output directly in dB into an 8-ohm load. They are the visual signature of the model and the feature HiFI-Stereo singled out in its 1989 listing. They are also the most legible thing about the amplifier from across a room.
Subsonic Filter, Tape Dubbing, and Speaker Switching
A subsonic filter engages at 17 Hz with a −12 dB per octave slope to strip out noise from record warps. Two tape decks can be connected at once, with a monitor switch for the signal being recorded and a dubbing switch that copies between decks regardless of the input selector's position. Two speaker switches allow either pair or both at once, and a mode switch flips to mono for checking left-right phase. Headphone output is 0.4 V into a 4-to-100-ohm load.
Historical Context
The E-303X is a modernized version of the 1978 E-303. The internal layout was reorganized away from the original's asymmetrical arrangement, the lengthy internal cabling was reduced, some push-buttons were eliminated, speaker terminals grew substantially, and a second line-level input was added. The power MOS FETs stayed, but the output stage went from two TO-3 pairs per channel to the triple push-pull arrangement described above.
Accuphase positioned the E-303X and its sibling E-305 for serious systems using floorstanding speakers that demand a large current reserve. The power supply is specified for 100, 117, 220, and 240 VAC at 50 or 60 Hz, which made it adaptable across markets. Power consumption is 90W at idle, 320W under the Japanese Electrical Appliance and Material Control Law rating, and 550W into an 8-ohm load at rated output.
Inside the chassis sit 108 transistors, 23 FETs, 17 ICs, and 103 diodes. That parts count explains the 20.5-kilogram weight and the density of the layout. A natural rosewood wood cabinet, the A-8, was sold separately at ¥16,000. It measures 466 by 190 by 385 millimeters, slightly larger than the amplifier's own 445 by 160 by 370.
Collectibility & Value
Asking prices for the E-303X have moved into serious territory. A serviced example listed by Retro Audio Berlin carried a €2,949 asking price in March 2026. A separate listing for the earlier E-303, not the X, was asking €2,300 in February 2026, which gives a rough sense of the premium the revised model carries. Listings for the E-303X itself have described units as cosmetically very good and working perfectly at 220 V. Others appear from Japan marked AS-IS, usually because of the 100 V native power supply.
Buyers should note the voltage question. The E-303X was built for multiple mains voltages, but many Japanese-market units are 100 V and need a step-down transformer outside Japan. A Russian seller's listing for an E-303 noted 100-220 V operation with defects present on the front panel. Cosmetic condition varies widely, and "working" and "clean" are separate questions.
On failures, the record is thin for the E-303X specifically. A YouTube repair series on the earlier E-303 documents a popping noise traced to the power supply, and LiQUiD AUDiO has published a repair writeup on the E-303 under a heading about its problems. Whether those apply to the X revision is not established. Service documentation does exist. A schematic is available, and a datasheet has been archived, so a competent technician has something to work from.
Replacement LED lamp kits for the meter and indicator lighting are available cheaply. One eBay listing sits at $24.50. That is an accessory, not the amplifier, and should not be mistaken for a market value signal on the unit itself.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.