Preamplifiers — Accuphase C-2150

The C-2150 is a stereo control center from Accuphase Laboratory of Japan, and it was the first preamplifier from the company to pair the AAVA volume control principle with a new noise-cancelling topology called ANCC. Accuphase describes it as offering a level of functionality close to its higher models, with a broad set of connections and two slots for optional boards.

Key specs that matter

Inputs comprise five unbalanced RCA sets labelled Tuner, CD and Line 1 to 3, plus two balanced XLR sets, CD-BAL and BAL, along with recorder REC and PLAY jacks and separate external preamplifier inputs in both formats. Outputs are two RCA line pairs and one XLR pair, rated at 2 V with a 50 ohm output impedance and a 7.0 V maximum into loads of 600 ohms or more. Frequency response is 3 Hz to 200 kHz within 3 dB, distortion is 0.005% for all inputs, while S/N measured with a shorted input is 110 dB. Input impedance is 40 kilohms balanced and 20 kilohms unbalanced, and channel separation is 74 dB at 10 kHz. Overall gain can be set to 12, 18 or 24 dB. The chassis measures 465 x 150 x 405 mm, weighs 16.9 kg and draws 34 W.

Engineering and use context

The AAVA circuit splits the music signal into 16 weighted currents from one half down to 1/65,536 and combines them according to the knob position, so no variable resistor sits in the signal path. ANCC adds a low-noise sub-amplifier that cancels noise and distortion in the main amplifier, and it is used in the I-V converter, the balanced output stage and the headphone amplifier, with the largest benefit at low and medium volume settings. Each channel has five unit amplifiers on separate boards mounted on a motherboard, fed by its own power transformer. Logic-controlled relays keep signal paths short, thin-film resistors cut current noise, and the input buffer follows the instrumentation amplifier principle. Bass tone control turns over at 40 or 100 Hz and treble at 8 or 20 kHz, each with 10 dB of range, and there is also a loudness compensator, a 20 dB attenuator, phase inversion per input and a mono switch.

Pairing

The rear slots accept the DAC-50 digital board with two AK4490EQ converters in parallel and USB playback of DSD up to 11.2 MHz, the AD-50 phono board for MM and MC cartridges with 30, 100 or 300 ohm loading, or the LINE-10 board for one more line input. The front headphone jack delivers 2 V into 40 ohms and suits headphones of 8 ohms and above. The RC-230 remote handles volume and input selection.

Alternatives

The Accuphase C-2300 is a later control center that moves to Balanced AAVA and a four-band tone control while keeping the same chassis size.