The Tubulus Concentus looks amazing! https://www.tubulus.net/product-category/i2s-cables/

I should have stated when ordering the AVPlay HDMI cables (above link) the seller will want to know what DAC/ Streamer you are using. The main reasons are for PCM and also DSD wiring which is not applicable in PCM1704 world. For basic I2S PCM play the AGD DACs need "PS Audio" compatible HDMI...

Congrats on your HE7S. The 1 ft. (0.3m) cables are a tricky challenge as the length and stiffness of the cable not wanting to bend make installation more difficult. But you are on the right track with using the shortest HDMI cables (lowest jitter) with these older DACs. The BlueJeans cable...

The annual holiday promotion sale from Audio GD is on. 7.5% off. http://www.audio-gd.com/En%20audio-gd.htm

@duffer5 Make sure the source providing I2S clocking is compatible with the DAC. I know on Gustard DDCs the signalling needs adjustment to be compatible with the Audio GD I2S method. Worth a try to check. Audio I2S over HDMI is an ad hoc approach with no standards.

Audio GD is having an anniversary sale. 5% off one item, 10% off with multiple item combo. http://www.audio-gd.com/En audio-gd.htm

@PLGA Have you tried selecting another input for one second and then switching back to optical? How long is your Toslink cable? Is the TV set to incompatible mode like multichannel surround? I never use optical but think I had a similar switching issue with I2S and the older PLL firmware...

@OCC7N The ACSS signals (current) are very small like +/-10mA across the pair.

You can order the DI20 with 75 ohm clock input. It is simply a resistor and connector swap.

Both my MK2 DACs restore external clock IF the 10M clock signal is present at time of powering on the DAC AND external cock was selected on prior power cycle ELSE internal. The DI20 used the operate like you describe - always booted internal clock. Had to change the DI20’s faceplate...

Opened up the HE7 mk2 and has the same yellow transformer as your R7HE mk2 and no 110 ohm resistor on the transformer. So clearly two different AES/EBU circuits used.

Correct… on pins 2 & 3 you can’t measure anything with an ohmmeter as the two red coupling caps block current. Best way to debug and know for sure is to use a scope. I would ask Kingwa about the 110 ohm resistor termination. He could have changed procedure during production.

Does your R7HE mk2 have the 110 ohm terminator across the transformer input. See pictures of my HE7 mk2 below? I think it is 110 ohm resistors as you can't measure across the transformer windings in circuit. Not sure what resistor that is with '001'. The red caps are in series with the...

.. add DI20HE I2S and elite 10M clock for A+ ! The reviewer used Roon Nucleus+ server with an AudioQuest Cinnamon USB cable to DAC. And internal Accusilicon XOs.

Underwood Hifi close to Atlanta, GA, USA sells and supports Audio GD. They supplied the DAC for review. And are listed as a "Worldwide Agent" for sales and support. http://www.audio-gd.com/Products-EN.htm