Preamplifiers — Accuphase C-3900S

The Accuphase C-3900S is a precision stereo preamplifier from the Japanese maker, with left and right channels kept fully separate, and it was introduced at a recommended retail price of EUR 32,200. It is the first Accuphase preamplifier to use a Dual Balanced AAVA volume control, and it sits in the current catalogue alongside the C-2900, C-2300 and C-57.

Key specs that matter

Sources connect through six line inputs on Cinch sockets and four balanced XLR inputs, and a dedicated EXT PRE input in both balanced and unbalanced form lets an external preamplifier or processor loop into the chain. Two balanced XLR and two Cinch line outputs feed power amplifiers, while PLAY and REC Cinch connections serve a recorder. Rated output is 2 V at an output impedance of 50 ohm. Frequency response is listed as 20 Hz to 20 kHz within +0 and -0.2 dB, with a distortion figure of 0.005% while S/N reaches 118 dB. The chassis measures 477 x 156 x 412 mm, weighs 25.3 kg and draws 60 W.

Engineering and use context

AAVA replaces a resistor-based attenuator with a set of voltage-to-current amplifiers that switch in and out to change level, which keeps any variable resistive element out of the music path. In the Dual Balanced version two fully balanced AAVA circuits run per channel, and ANCC noise correction is integrated into them, which the maker says lowers noise by around 15% against the predecessor. At the front of the signal path sits a discrete current feedback input amplifier with high gain, and the output uses eight amplifiers in parallel. Left and right channels each have their own toroidal power transformer, filter capacitor bank and unit amplifier, and the circuit boards are made from glass cloth fluorocarbon resin. The volume knob drives a quiet sensor rather than a potentiometer and can be moved by remote. Front-panel functions include a five-stage loudness compensator, a balance control with finer steps and a discrete headphone amplifier on a 6.3 mm jack with selectable gain. The case is finished with a natural-grain wood cabinet.

Pairing

The rated output level and low source impedance suit the input stages of standard high-performance power amplifiers, and the twin balanced outputs allow two amplifiers to be driven at once, for example in a bi-amplified system. Owners using a surround processor can route its front channels through the EXT PRE input so the C-3900S handles both stereo and home cinema.

Alternatives

The Accuphase C-2900 is the smaller preamplifier in the same range and also uses AAVA volume control.