Hi Russ,
I received a dual-mono kit of 9028pro the day before yesterday. Yesterday I assembled the dual-mono system and am now testing the sound of dual-mono system.
For audio signal transport, I used Hermes-BBB/Cronus boards as a clock master (45/49 clocks on board) and transport. The VDD-XOs from both of the master and slave DACs were removed with the slave sharing the same master clock from the master. A Mercury board was used for analog output with the output wiring as indicated by the instruction.
I used the slave as the right channel by placing jumper between GPIO 11 and 12 pins. Though this may be redundant, I placed a jumper between 11 and 10 on the master to secure its DAC address. Correct me if this is not necessary. Also, pin 1s were connected each other between the DACs as indicated.
For music player, I used an MPD capable of DSD512 running on a debian stretch with Botic driver and a HQ player running on an Ubuntu 16.04 linux system (i7 8700k) with its output to this debian system as NAA.
Results:
First of all, the dual-mono firmware (kindly enclosed in the kit, thanks Brian) worked very well. I've never experienced any annoying noise in playing music through this experiment. On MPD, both of PCM and DSD (up to DSD256) provided very clear sound but the system failed to play a DSD512 source: falling into a muted condition, though the software was still working. The HQ player which was set to playing only DSD worked up to DSD256 as well but also failed to play DSD512. Interestingly, the SQ of HQP in playing DSD became quite dull, losing its well acknowledged ability to produce good SQ.
The failure to play DSD512 may be due to sharing the MCLK between the master and slave. In this meaning it may be difficult to find any advantage of dual-mono with external clock master. PCM/DSD on MPD was not bad but so far it appears that this dual-mono system can not replace a single 9038pro with TrueSync setup.
There may be something wrong with my setup. If so, please let me know, thank you.
Regards,