HDMI switches with spdif breakout

I’m currently using an HDMI 4-input switch that provides optical and coax digital (spdif) outputs to ‘break out’ the digital audio from my ARMX6. This lets me play a wider range of sample rates, etc, into a decent outboard Audio DAC.

The one I use is a MonoPrice HDX-401TA. Overall it works fine but has one minor snag. If I switch from using my Linux box to the ARMX6 the ‘ReadEDID’ fails. This prompts me to ask if anyone else is using an HDMI switch in a similar way, and if so, what model and how they are getting on.

the ‘ReadEDID’ fails

Does RISC OS patiently wait for a monitor to be connected and then ask for EDID information? It seems strange that an HDMI switch doesn’t do just that. (switch)

The switch is being set to connect the ARMX6 to the monitor before the ARMX6 is powered up.

Additional info: After starting this thread I experimented. With the HDMI switch powered after having shut down my Linux box I switched the HDMI to the ARMX6. The switch also has a choice of two audio modes. One called ‘2channel’ the other ‘5.1channel’. By default this powers up as the latter.

I switched this also to ‘2ch’ and then back to ‘5.1ch’. (Confirmed by a relevant LED on the switchbox.

Having done this when I powered up the ARMX6 I did not get the problem.

Which makes me think it is a quirk of the HDMI switch, or at least the fact that there is a switch between the monitor and the ARMX6. However the above may have been a fluke. I’ll need to repeat the test.

Despite the labelling, I think what actually happens is that the switch for the audio mode actually switches between presenting/supporting the list of audio modes the switch will accept and pass out via spdif with the list the monitor may accept. But again, with only one switch and monitor I can’t really explore this.

The odd thing is that the entire setup seems to have been powered down for many minutes to clear the behaviour. The monitor has a flashing LED that continues for a few mins after power is removed. But if I power things up as soon as that stops flashing, the problem appears. I have to wait much longer for it to clear itself. Yet the HDMI eats power. It has a set of bright LEDs and gets quite hot in use. Draws well over an amp at 12V. And when powered off, the LEDs die within a second. So I find it hard to convince myself that something inside it ‘remembers’ for so many minutes longer! Curious.

And once the problem has shown, later uses of the ReadEDID command fail with the same error.

Just tried the ‘switch audio mode back and forth’ again. This time, no success. I still got the ReadEDID error. So it looks like the previous case was a fluke or down to something else I did without realising it would affect things. :-/

When you switch off the Linux box, does it still have mains connected and on at the PSU? It may be retaining power to the KVM via USB if the PC is in standby-off mode, just waiting for the front power button to be pressed to start it again.

The linux machine is still connected to the mains. But there is no ‘KVM’.

I use an HDMI switch to choose which machine is connected to the monitor. And a passive USB switch to switch the keyboard, mouse, etc, between machines.