My I2s ground potential/interference problem


This is what my display looks like (black display flickering) with DS main power switch off and mains power lead removed. The moment I remove the I2s cable to my source the flickering stops and DS display looks normal (i.e. off).



It looks like there’s enough current being provided over the I2S cable to power up the processor and display. There’s a 5V line on the I2S connector with a poly fuse but I’m surprised that there’s enough current available and going thru the fuse to try to power up the processor and boot the FPGA, etc. I don’t think it’s a good idea to leave your I2S cable plugged in with the DS powered off (in the back.) Having the DS in standby is fine.


I am always leaving the DS in standby with power connected.

I also had the same problem with another source (also from Audiobyte/Rockna).

The problem persists independent of firmware upgrades.

I have the flawed display with the vertical moving stripes.

I am more worried if this affects the SQ of the DS, but I understand from your answer that this isn’t a voltage potential problem or ground loop, but rather a DC power over I2s from the source that powers the DS, even with DS mains switch off. Should it work like this - really?


Should it work this way? There isn’t a standard for I2S and different companies have made different assumptions about each of the signals on the HDMI connector, including who provides power, etc. The DS (and PWD) provide power thru a fuse so that they don’t provide more than they are designed for. Without more formal specification of an I2S interface over HDMI connectors there are bound to be incompatibilities of varying degrees between different companies.



It certainly is not intuitive for the owner to see a DAC ‘trying’ to power up without its power lead connected. It surely confused me…


If I’d have expected it I would have either added a software controlled load switch/relay or managed some sort of circuit equivalent to a diode (but with no diode voltage drop.)

Still there’s likely some other incompatibility to be found with still other manufacturer combinations… There’s a reason USB, HDMI, etc. specs are so complicated…