DACs — SMSL SU2

The SU2, also written SU-2, is a compact desktop DAC from the Chinese company SMSL, built around the ESS ES9039Q2M converter chip and a fully balanced analogue stage. It is a pure converter with no volume control, headphone output, USB input, Bluetooth or remote, and it is aimed at studio monitoring chains, active speakers and near-field desktop systems. In the US it sells at USD 99.99, and in France it costs EUR 109.

Key specs that matter

Three digital inputs are provided - coaxial S/PDIF, Toslink optical and AES/EBU. The decoder accepts PCM from 16 to 24 bit at 44.1 kHz to 192 kHz and DSD64 carried as DoP. Outputs are one balanced XLR pair at 4.7 Vrms and one single-ended RCA pair at 2.3 Vrms. SMSL specifies THD+N of 0.00006 percent (-123.5 dB) on XLR and 0.00008 percent (-121.5 dB) on RCA, and both the noise figure and the dynamic range are 130 dB via XLR and 126 dB via RCA. The metal case measures 150 x 42.5 x 133.1 mm and weighs 532.6 g. It runs from 100-240 V AC mains, drawing under 2.3 W in operation and under 0.1 W in standby.

Engineering and use context

After the ES9039Q2M, the analogue stage uses four OPA1612A op-amps, two per channel, so the signal stays balanced from the chip to the XLR sockets. The CK-03 clock module, an in-house circuit that SMSL also fits in other models, is there to reduce jitter on the incoming digital stream. The AES/EBU input is less common at this price, and it lets the SU2 take a signal from professional interfaces, transports and mixers. Leaving out USB means the unit needs a streamer, CD transport, computer interface or TV with a digital output ahead of it. Instead of a screen, front-panel LEDs show the selected input, signal lock, channel activity and sampling rate. The unit detects the active input by itself and restores the last setting after power-off. Mains power goes in through a standard AC cable, so there is no external adapter, and the box holds only the DAC, the mains cable and the documentation. With no attenuator inside, every change of level has to be made on the equipment that follows it in the chain.

Pairing

The XLR pair suits active studio monitors and power amplifiers with their own level control, or a preamplifier or headphone amplifier with XLR inputs, while the RCA output covers integrated amplifiers.

Alternatives

The SMSL SU-1 is a DAC built on the AKM AK4493S with an XMOS XU-316 USB input handling up to 32 bit and 768 kHz, DSD512 and MQA decoding on all inputs.