DACs — Audio Note DAC 3.1x/II Balanced

The DAC 3.1x/II Balanced is a full-size D/A converter from the Audio Note (UK) catalogue built around the 18-bit Analog Devices AD1865N chip and a transformer-coupled valve output stage. The design follows the company rule of omitting oversampling, jitter correction, noise shaping and clock recovery stages, and it is offered with a front panel in anodised aluminium or black acrylic, depending on the chosen finish.

Key specs that matter

There are two digital inputs, a 75 Ohm RCA socket for S/PDIF and a 110 Ohm XLR socket for AES/EBU, and the converter handles sample rates of 44.1, 48 and 96 kHz. Audio Note gives a reference output of 3.2 V RMS with output impedance below 10 Ohm whether the XLR or RCA outputs are used, with a left to right balance better than 0.2 dB. The valve complement is two ECC82 or 5814a double triodes, one ECL82 and one 6X5 rectifier. The chassis measures 145 mm high, 450 mm wide and 425 mm deep and weighs 15 kg.

Engineering and use context

Audio Note argues that music is a continuous signal in time which is damaged when it is broken up and corrected, so it removes the digital processing stages found in most converters. Filtering is handled in the analogue domain instead, which the maker says keeps phase behaviour coherent. The filter transformers used for this job come from the company's own design and production. After conversion, the signal passes through an ECC82 or 5814a valve stage and on to an output transformer, which also provides the balanced connection. The 6X5 valve works as the rectifier in the power supply, so the unit uses valve rectification rather than solid state diodes for its high voltage rails. With both S/PDIF and AES/EBU on board, it can accept a transport or streamer fitted with either type of digital output.

Pairing

The balanced output makes the DAC 3.1x/II Balanced a natural partner for preamplifiers and integrated amplifiers with XLR line inputs, while the single-ended option covers RCA-only equipment. The very low output impedance allows longer interconnect runs without concern about loading. On the source side, an AES/EBU transport uses the XLR input, and one with a coaxial output uses the RCA socket. Its width lines up with the full-size Audio Note preamplifiers and power amplifiers for a uniform stack.

Alternatives

Higher in the same range, the Audio Note DAC 4.1x Balanced keeps the AD1865N converter and the same casing but moves to a 5814a and 6463 valve output stage based on the M6 line preamplifier.