Over the last number of years, we have seen a proliferation of DACs from Chinese manufacturers offering models of increasingly better resolution - higher fidelity - and greater feature set. These days, I am of the opinion that we have achieved way above and beyond the ability for human hearing to differentiate these machines unless the manufacturers purposely added some kind of "coloration" to the analogue output whether it be frequency response or changes to the noise and distortion levels (the "tube sound" being a prototypical example we may come across).
For many devices these days, opening the manual will show us technical information like the frequency response of the filters in this example. I think this is a nice evolution among manufacturers recognizing that showing product performance is important to educated customers with graphs and technical details rather than mere prose which often provides little satisfaction for the consumer's intellect.
Today, let's start a multi-part look at this DAC; no need to hurry because I think the performance at this price point warrants serious consideration and the many ways and features one can gather performance metrics on (I don't promise to test everything of course!). Obviously it's not an expensive device, has a remote controller, has both unbalanced RCA and balanced XLR outputs, Bluetooth 5.0 input, capable of up to 32/768 PCM and DSD512 (1-bit, 22.6MHz) using USB 2.0, along with S/PDIF TosLink and Coaxial inputs for up to 24/192 and DoP DSD64. No money wasted on MQA licensing. Depending on what we find, this might be right for you...
As a DAC, this device internally uses dual ESS ES9038Q2M DAC chips. These Q2M chips have become quite popular with many mobile and desktop applications thanks to the fact that they are low-power chips yet provide excellent performance from the dual channels; each chip capable of stereo or mono operation. They are the "little brother" of the top-of-the-line ES9038Pro with 8 channels. And like the ES9038Pro, these Q2M's also can function in both voltage and current modes.
Just as the chips are like the little sibling to the top-of-the-line device, the way the SMSL DO100 is designed is reminiscent of the design of the Topping D90SE we talked about last year. The idea here is similar; both are driving the DACs in current mode, and both are using high quality TI OPA1612 opamps for current-voltage conversion (I/V C). A difference of course being that the DO100 only requires 4 sets instead of the 8 found in the D90SE.
Based on the datasheet, these ES9038Q2M chips are rated as THD+N -120dB, and DR 129dB(A) when operating in differential current mode. Any DAC capable of this level of performance assuming everything else like linearity, frequency response, and jitter look good will already place the device in the upper echelon of the highest performance DACs out there.
Press and hold down on the control knob to turn on / off. You can also use the control knob to change menu items and click to either register a change or toggle between parameters - all quite intuitive. Parameters include which digital input, filter settings FL1-7, DPLL 1-9 jitter tolerance (higher values might be needed to increase S/PDIF tolerance for some devices like TVs, I think my default was 3), UAC1/2 (use UAC2 mode for modern hi-res USB 2.0 performance with DSD), and screen brightness 1-5.
[DPLL refers to the "Digital Phase Lock Loop" which is part of the "Jitter Eliminator" circuit. This parameter adjusts the bandwidth for the timing of the input signal in order to maintain a lock. With highly jittery sources like say an old CD transport, if you hear crackles or pops, you might need to push the value higher. It has been said that keeping this value as low as possible (ie. keeping at 1) could improve sound quality. I have not personally been able to verify this. I'm guessing this parameter is only meaningful for the S/PDIF inputs.]
Power, volume (levels from 0-99) and input button