Split audio out (3.5MM) of HDMI?

d_brennen · 18 Oct 2020 at 13:03

Situation: I have monitors that I'm happy with but they don't have audio out. I want to plug in various HDMI devices (console, raspberry pi etc) and have 3.5mm audio out to speakers or headphones. I've seen some cheap eBay specials that do this but has anyone experience of doing this? Not really a job for an AV receiver as it's occasional desktop use...

E: monitors are FreeSync 75hz max, 3 devices say

lucid · 18 Oct 2020 at 13:47

The audio de-embedders will work. You might need to check that the audio signal is set to PCM stereo at source though unless you buy something capable of decoding, but that won't fall in to the 'cheap' category.

The output from the de-embedders will be analogue stereo. Whether that's via a 3.5mm jack or a pair of stereo RCA connectors makes no difference, the signal itself is still analogue stereo.

Get an appropriate lead to connect to your speakers - probably jack to jack - and you're in business.

Driving headphones is something different. The output from the de-embedders may be too low for that, and the volume level will be fixed at a certain point, so you won't have a way to make the sound louder or quieter. You will need a headphone amp to fix both these issues.

d_brennen · 18 Oct 2020 at 15:22

Good stuff, thanks. Many of them mention HDMI 1.4, if / when I upgrade my GPU, do you know where I stand with regards to HDCP? Also, FreeSync if I run my PC through an extractor?

lucid · 18 Oct 2020 at 16:02

You're going to need HDMI 2.0 at least, I think.

The Wikipedia page for HDMI standards is pretty good. It has a table which crossreferences the various features against which HDMI version is required for support.

Just a thought, but wouldn't this be easier to do with a PC sound card? Either an internal or a USB external. That would free you from these restrictions and maybe even allow you to run with Display Port.

d_brennen · 18 Oct 2020 at 18:04

lucid said:
You're going to need HDMI 2.0 at least, I think.

The Wikipedia page for HDMI standards is pretty good. It has a table which crossreferences the various features against which HDMI version is required for support.

Just a thought, but wouldn't this be easier to do with a PC sound card? Either an internal or a USB external. That would free you from these restrictions and maybe even allow you to run with Display Port.

Not sure what you mean? I'm looking to run devices that output audio over HDMI and split that out to my speakers. Currently my speakers are plugged into the PC but it's a faff to get behind the computer and monitor to plug in a guest device and some don't have a 3.5mm jack anyway. My thinking was to have an audio extractor/HDMI hub on the desk and just leave the speakers plugged into that

lucid · 18 Oct 2020 at 18:31

My apologies, I remembered reading 'monitors' in your OP but forgot about the Pi and console. Forget the sound card idea. It's not appropriate here.

You still have a bit of a bottleneck in the de-embedder if you want to run high frame rate stuff though.

Does your console and the Pi have alternative audio out sockets?

d_brennen · 18 Oct 2020 at 19:30

Pi has 3.5mm but it still means clambering behind everything to plug stuff in, was thinking of getting either a Series S or One X to make use of game pass but I believe neither of these have 3.5mm sockets? Not sure, but in any case it'd mean plugging stuff in and out and I'm lazy

Not really fussed over anything higher than 1080/60 but I do set the frame rate target to 75fps, my monitors max supported. FreeSync is the dog's danglies though, don't want to lose that and can't find out if these switchers/extractors mask the monitors capability from the machine...

I'll email some suppliers/manufacturers, hopefully they'll understand what I am asking

lucid · 18 Oct 2020 at 21:26

I understand what you're asking, and have answered that you will need at least HDMI 2.0 in the de-embedder. The reason is partly HDCP / EDID restrictions, and partly the bandwidth required to pass the signal.

What I have been trying to do is steer you towards thinking about a solution that retains the ability to use higher frame rates without paying through the nose for a device to get an audio signal when these signals are already available direct from the devices.

Good luck getting some answers from the resellers.