Simon Price
Aune S9c Pro Review : It’s rare you get DACs that perform ridiculously well at the sort of money of the Aune S9c Pro which retails for $700/£600.
This is partly why I asked this brand to sponsor me and you will notice the banners on the website now….. because I love the economies of scale and pure out and out value that many Chinese products provide. It essentially means, to my mind, any fan-boy who professes that a certain local brands designers know-how makes products best, is circumvented by pure economics and good design for what is possible at price.
If you have not checked this product out you should do so. Units can be bought or trialled in the UK from dealer / distributor Eden Audio, whose website is here. Contact Adam and let him know you saw my video. This is a gem of a product at this price. Product link here
Watch my YouTube Video here
More Questions I asked of Aune….
1. Why is there no on/off switch or knob at the front and only a rear switch?
Because we found that many users prefer to completely cut off power. The power off function on the front panel in our previous design was rarely used. Maybe usage habits vary from region to region.
2. Upsampling or oversampling DAC on any of the inputs?
There is oversampling which is a necessary processing step for DACs based on the Multibit Sigma-Delta Modulator.
3. Is USB deemed the best input of this DAC by sample rate but by anything else?
In terms of the range and diversity of input bitrates and formats, USB input is indeed the best. However, in terms of signal quality, there is not much difference between USB and other inputs.
4. I can hear the sound is a little more balanced when you feed it high sample rate audio over the USB input compared to lower sample rate music on the same input and coaxial RCA input. Is this down to the way you say it ‘Outputs different frequencies corresponding to different resolutions’ when talking about the PLL. Can you explain that.
Indeed, the processing is different because higher audio sampling rates require a higher clock frequency, and a higher clock frequency allows for more detailed processing in the PLL.
5. Is the DAC fully MQA compliant and doing full unfold of the MQA signal – if say connected to my Bluesound Node 2021? Is MQA only on USB input or other inputs?
The S9c Pro fully supports the identification and full decoding (Full-Decoder and Renderer) of MQA only when using the USB input. When the data stream is an MQA signal, the S9c Pro will automatically process it. The USB output of a source device needs to support USB 2.0 AUDIO device driver automatic recognition.
6. Do the DACs work in Dual mono mode – ie one per channel?
Yes, one ES9068 for each channel. Two DACs in total.
7. As I understand it the coax/optical and AES converts the signals to I2S (I squared S), which forms the signal into timing and clock signals separately so you can rebuild the signal. Is that right? As I understand I2S is basically clock signals and data signals on different HDMI pins. Is this so when it goes into the PLL you take any distortion away from the combined effects of clock and data signals being combined or is there another explanation?(A PLL in lay terms is I understand to match the frequency of the incoming audio signal to eliminate jitter – jitter being time distortions in the audio that affect SQ)
This question can be answered in two aspects. In the I2S signal, the clock signal needs to be synchronized with the data timing. Among the three clock signals, MCLK is the most important, and the other clocks are derived from a frequency division of MCLK. The accuracy and jitter of MCLK determine the accuracy and clarity of the DAC demodulation signal, so the signal distortion is reduced; We incorporate a phase-locked loop (PLL) to process the MCLK in the I2S signal, removing the quality issues in the original MCLK while maintaining high synchronization between the processed MCLK and the original signal. If they are not synchronized, it may cause inconsistent signal delays of different frequencies in the DAC output, thereby affecting the listening experience.
8. The USB signal doesn’t have to be converted to I2S as it is already I2S on a rail on the USB cable? (When Aune are talking about differential transmission on website) Is this right?
The USB transmission uses the transmission method specified in the USB protocol, which has already dispersed I2S audio data into many fixed-capacity data packets for transmission. These packets are equipped with transmission verification to prevent data errors. There is a significant difference between data packets and the I2S signal stream. When the data is transmitted to the XMOS internal system, it undergoes packet decompression, subsequently restoring the original I2S signal stream. Therefore, XMOS, as a USB transmission, is asynchronous compared to a computer player.
9. Can you explain the bit about sharing the clock signals of the DAC and XMOS in lay terms, per the segment of your website headed ‘clock sync tech for the 16 bit usb core framework’
The XU316 used in the S9c Pro is a programmable chip with 16 processing cores. The system clock used for USB communication and the audio signal clock are completely separate. We provide the clock used by the DAC to the audio processing section of the XMOS simultaneously.
10. Can you explain exactly what is going on with clock sync and how this is different to other DACs in the easiest lay language not pre-supposing any knowledge.
It’s like a musician playing the piano where the beats fluctuate, sometimes faster, sometimes slower, and cannot guarantee consistency from start to finish. It can also be understood as the pitch variation caused by the speed instability (Wow & Flutter/ WRMS) of old LP record players. Although the clock quality of modern DACs is generally high, as a professional audio manufacturer, we have higher aspirations. The actual results also prove that better synchronization levels lead to higher sound quality.
11. What exactly is going on with the mode 2 and mode 1 tuning modes – I can hear what you describe – but how exactly is as you say “fast locking and low latency” (mode 1) accomplished in contrast to more precise clock signals (mode 2). Why not just offer mode2 if more precise? Please can you explain this in lay terms.
Fast locking differs in PLL stabilization time. When solely listening to music, sample rate changes are infrequent, and the slight pause between switching songs with different sample rates does not affect the user experience. However, when the device is used for daily entertainment purposes, there can be frequent sample rate changes, especially in some gaming audio where the sound quality requirements aren’t very high but interruptions in sound affect the user experience.
