C-3900S At A Glance

• Topology: Dual Balanced AAVA volume control with two separate balanced AAVA circuits, one per channel
• Construction: Full dual-mono — separate left and right amplifier blocks, separate toroidal transformers, separate filtering, separate unit amplifiers
• Power supply: Six 10,000 μF filtering capacitors per channel
• Noise floor: 0.91 μV operating noise at –18 dB (a 15% reduction from the C-3900 it succeeds)
• Chassis weight: 25.3 kg
• Input stage: High-gain discrete current-feedback amplifier with ANCC noise/distortion reduction
• Output stage: Eight parallel output amplifiers per channel
• Headphone amplifier: High-performance dedicated headphone stage
• Loudness compensator: 5-stage with finely adjustable balance control
• Construction details: Glass-cloth fluorocarbon-resin PCBs; natural-grain wood side panels with mirror finish

The C-3900S is Accuphase's flagship line preamplifier — the S-revision of the 50th-anniversary C-3900 introduced in 2022, now in its current production form following the C-3900S world premiere at Accuphase's Yokohama headquarters in early 2026. The S is not a cosmetic refresh. It is a measurable advance: 15% lower operating noise, a heavier chassis, doubled per-channel filtering capacitance in a fully dual-mono arrangement, and engineering refinements to the input and output stages that the original C-3900 did not have.

Dual Balanced AAVA — two complete volume controls, one per channel. The AAVA volume control is Accuphase's distinguishing technology: a current-domain summing volume control with no moving wiper in the signal path, no resistor-ladder switching, and no measurable change in noise or distortion across its range. The C-3900S takes the AAVA idea further by running two complete balanced AAVA circuits — one for the left channel, one for the right — in full dual-mono construction. Each channel has its own input amplifier, its own AAVA circuit, its own power supply rails, its own output amplifier, and its own filter capacitance bank. Cross-channel signal contamination is eliminated at the topological level, not merely minimized by good layout.

The noise figure that matters. Accuphase's published operating noise figure for the C-3900S at –18 dB attenuation is 0.91 μV — a 15% reduction from the C-3900's 1.07 μV at the same setting. At normal listening levels in a reference system, a noise reduction of this magnitude makes audible difference in the bottom octaves and at the very quietest passages where reverb tails and recording-venue noise live. This is the design choice Accuphase made when deciding whether the C-3900 needed an S-revision at all: the only justification was a measurable, audible improvement, and the company chose to deliver one.

Six 10,000 μF caps per channel, in full dual-mono. The C-3900S's power supply uses six 10,000 μF filtering capacitors per channel — twelve in total — arranged in full dual-mono with separate toroidal transformers per side. The capacitance per channel exceeds that of many full power amplifiers; this is the kind of supply reserve that prevents low-frequency transients from intermodulating against the supply rails and producing harmonic distortion at the output.

Discrete current-feedback input amplifier with ANCC. The input stage is a high-gain discrete current-feedback amplifier — not an integrated-circuit op-amp — paired with ANCC, Accuphase's Active Noise Cancelling Circuit, which actively cancels noise originating in the amplifier's own internal stages. Below the AAVA, eight parallel output amplifiers feed the line and balanced outputs; the parallel arrangement reduces output-stage noise and lowers the unit's output impedance.

Chassis and aesthetics. The C-3900S chassis is heavier than the C-3900 — 25.3 kg, an increase that reflects additional internal bracing and the heavier dual-mono transformer and capacitor bank. Side panels are natural-grain wood in a mirror finish, crafted in the Yokohama facility using selected virgin wood. The faceplate carries Accuphase's brushed-gold finish; the chassis sits on high-carbon cast-iron isolator feet.

For existing C-3900 owners. The C-3900 is not made obsolete by the C-3900S. The original is still a reference-grade preamplifier, and the differences are at the level that rewards exact-match listening rather than casual auditioning. For new purchases of a flagship Accuphase line preamplifier, the C-3900S is the current model and the one Accuphase recommends.

System pairing. The C-3900S is engineered for use with Accuphase's A-300 monoblocks, A-80 or A-48S stereo power amplifiers, or P-7500 / P-4600 Class A/B stereo amplifiers. It functions equally well as the line stage in a system fed by the C-57 phono preamplifier for vinyl, or by the DC-1000 / DP-1000 reference digital pair.

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