Preamplifiers — Accuphase C-3900

The C-3900 is the top precision stereo preamplifier from Accuphase, the Japanese electronics maker based in Yokohama. Development began to mark the company's 50th anniversary and took five years, and the C-3900 was introduced in 2020 as the culmination of Accuphase's AAVA volume-control work. It was later succeeded by the C-3900S, which cut noise by a further 15%.

Key specs that matter

There are four balanced XLR and six single-ended RCA line inputs, with two balanced and three single-ended outputs. Volume is set by Dual Balanced AAVA, and the input stage is a high-gain discrete current-feedback amplifier with ANCC noise-cancelling circuitry. Left and right channels have separate toroidal power transformers, filter capacitors and amplifier units. A headphone amplifier is built in. The chassis measures 477 x 156 x 412mm and weighs 24.6kg, and it sits in a natural-grain wood cabinet.

Engineering and use context

A conventional preamplifier sets volume with a resistive attenuator, which changes impedances and adds noise. Accuphase's AAVA (Accuphase Analog Vari-gain Amplifier) takes the resistive attenuator out of the signal path. A set of V-I converters with different gains turns the signal from voltage into current, and each volume position switches a combination of these converters, changing the amplifier's gain directly. Impedance and frequency response therefore stay constant at every setting, and noise stays low at the levels most used in practice. Balanced AAVA joins two AAVA circuits in a balanced connection, and the Dual Balanced AAVA of the C-3900 runs two such balanced units in parallel, lowering noise by about 30% compared with earlier Accuphase preamplifiers. The volume knob does not turn a potentiometer. It drives an in-house position sensor inside a precisely machined block of extruded aluminium for accurate angle detection. Circuit boards use glass-cloth fluorocarbon resin for low dielectric loss, and in the dual-mono layout the channels stay electrically independent to minimise crosstalk.

Pairing

With this many inputs the C-3900 works as the control centre of a complex system with several sources, phono stages and DACs among them. The balanced outputs suit long runs to Accuphase power amplifiers such as the A-300 or the M-series monoblocks, and the extra pair of outputs lets a subwoofer or an additional amplifier for bi-amping be connected.

Alternatives

The Accuphase C-2900 brings Balanced AAVA to a less expensive preamplifier placed below the C-3900.