The main improvements in the new version of PRO2 are:
1. Adopting AKM's fourth generation flagship DAC: AK4191+two AK4499EX chips as the main chips for analog-to-digital conversion;
2. The crystal oscillator in the USB section uses a femtosecond clock combined with our self-developed constant temperature bath to enable the clock system to operate in a constant temperature environment;
XMOS has been upgraded to the new XU316 chip as a USB Audio solution, supporting up to DSD512 and PCM 768K sampling rates.
4. Upgraded the specially optimized ultra-low noise power system, solving the problem of high low-frequency distortion in AKM DAC;
5. Equipped with digital front-end, supporting volume adjustment, analog high and low gain adjustment, OLED brightness adjustment, and screen off playback; When inputting I2S, it supports up to DSD1024.

SDA-6 is a high-performance DAC developed by our Singxer team, which uses AKM's fourth generation flagship DAC: AK4191+two AK4499EX chips as the main chips for digital to analog conversion; AK4118 serves as a digital audio input receiver chip, using STM32 as the control core of the entire machine, and Xilinx's large-scale FPGA as the clock system and digital audio stream processing. PCM supports up to 768Khz, DSD supports native direct decoding, and supports up to DSD512.
The DAC chip adopts two AK4499EX chips released by AKM in 2022; DSD can choose the native direct solution mode, and the DSD digital stream does not pass through internal digital filters, working in NOS mode, which fully conforms to the design concept of HQLayer.
It has rich input and output interfaces, including standard USB2.0 input interface, SPDIF and BNC coaxial and AES balanced input, HDMI-I2S input interface, analog output including XLR balanced output and RCA single ended output; The full interface supports DSD input.
SDA-6 PRO supports external clock input, with USB supporting 10M clock input and other interfaces supporting WCK input. In USB mode, it also supports switchable input impedances of 50 and 75 ohms.
Main technical features:
1. Our independently developed adaptive clock system technology includes four independent ultra-low jitter audio crystal oscillators, and a femtosecond level local clock system is configured for the USB part. Combined with our self-developed constant temperature technology, we achieve constant temperature crystal oscillators.
2. High performance mixed signal phase-locked loop, excellent clock synchronization recovery technology, can significantly filter the secondary PLL of external digital input jitter;
3. Adopt 4-channel fully balanced full DC Class A discrete circuit output;
4. Large FPGA for digital audio signal processing, self-developed third-generation algorithm, and innovative multi input channel isolation technology ensure the purity of each input signal.
5. Built in 40 watt customized O-type transformer, outputting 4 independent power supply windings, up to 20 sets of distributed voltage regulation lines; The reference power supply provided for AK4499EX is a newly developed chao low-noise (as low as 0.3uV RMS) power system.
All versions support switching between 115V and 230V AC voltage, with an internal switch.
Technical indicators:
Sampling rates supported by each input interface:
PCM: 44.1KHz,48KHz,88.2KHz,96KHz,176.4KHz,192KHz,352.8KHz,384KHz,705.6KHz,768KHz
[Among them, USB and I2S support all sampling rates, and S/PDIF supports up to 192KHz]
DSD: 2.8 MHz (DSD64)   -  DoP,native
5.6 MHz (DSD128)  -  DoP,native
11.2 MHz (DSD256) -  DoP,native
22.5792 MHz (DSD512) -  native
45.1584 MHz (DSD1024) - native, I2S input only
USB and I2S support all DSD formats, while S/PDIF and AES/EBU support DSD64 DOP mode
Bit width: up to 32 bits over USB and I2S
               up to 24 bits over S/PDIF

Electrical standards for each interface:
1. The USB input socket is a standard USB-B type female socket, with a USB power supply range of 4.5V-5.1V;
2. The SPDIF interface inputs standard S/PDIF signals with an input impedance of 75 ohms and an AES input impedance of 110 ohms;
3. The power input is 115V/230V AC, and a 40 watt customized transformer is used internally for power supply;
4. I2S input is LVDS level in HDMI interface form, compatible with most front-end devices;
Analog output performance:
Output level (0dBFS):
PCM: RCA single ended output is 2.3V RMS, XLR balanced output is 4.6V RMS
DSD: RCA single ended output is 2.3V RMS, XLR balanced output is 4.6V RMS
Output impedance: 22 ohms (RCA single ended)/45 ohms (XLR balanced)
Frequency response: 20-20kHz+/-0.1dB
SNR: 130dB (20-22kHz A weighted)
Distortion characteristics:
THD+N (1kHz, 0dBFS) 0.00012% (-118db) at fs=44.1Khz (PCM, 20Hz-22kHz A weighted)
Dynamic response (1kHz, -60dBFS) 131dB (20Hz-22kHz A weighted)
Size and packaging:
Size: 262MM * 220MM * 46MM (excluding the height of the legs and the protruding part of the connectors at the back of the chassis)
The weight of a single machine is approximately 2.7KG.
The length, width, and height of cardboard packaging are 330MM * 310MM * 110MM
Shipping packaging weight approximately: 3.6KG
Accessories: USB cable x1, power cable x1, infrared remote control x1.

New test data to be updated
 
The following is the test data for the SDA-6 PRO production version, based on APX555: