No Audio Output with OSSC 1.6 fm 0.78a

[nye678]

Hi, I just got my OSSC today and while trying it out I cannot seem to get any audio output from HDMI. I’ve tried a Genesis with SCART and the Dreamcast using VGA with the audio routed to A3 IN. With SCART I do get audio from the 3.5mm audio jack though.

The model is the new 1.6 and the screen shows 0.78a for the firmware revision.

I stupidly didn’t get the remote, not realizing that I can change any options without it. So if I do need one to resolve this can someone please recommend one that is easily sourced in the US? I was going to try updating the firmware with ossc_0.78-aud not being sure if the a in 0.78a meant audio, but then found out I can’t upgrade without a remote or jtag programmer.

[BonzoBits]

Logitech programmable remotes work fine. I think the OSSC wiki has more details.

[Morpheus_79]

But maybe it should be mentioned:
The ‘a’ in the displayed ‘0.78a’ stands for ‘audio’ – so you already have the latest correct firmware for outputting audio. And aside from the ‘TX mode’ setting (which should be set to ‘HDMI’ by default… while i don’t know for sure, if setting it to ‘DVI’ actually disables audio output), there are no options for specifically disabling/enabling audio.

[nye678]

So I have found a remote around the house that is compatible and have verified that the TX mode is set to HDMI. Also tried fiddling with all the other options but nothing affected the sound. I tried re-flashing 0.78a, and also downgrading to 0.77a. Neither of which had any effect. I’ve done a visual inspection of the board and everything looks alright. And I’ve swapped the OSSC out for my cheapo scaler to verify that the console, tv and cables are all functional, which they seem to be.

Any ideas for next steps? I have an old analog oscilloscope and an fpga board I can use as a logic analyzer. But I am not very skilled with those tools yet.

[Morpheus_79]

As i wrote here:

i’ve build a couple of 1.6 OSSCs over the last months – 3 of ’em had no audio output. I suspected the ECS-3X9X 24.576 MHz quartz crystal… and was right. On all three boards i had accidentally created a small solder bridge between the two pins of the quartz. Sadly somehow on the top side of the pcb, between the casing of the quartz and the board itself.

Maybe(?… with a big question mark, since you bought a preassembled OSSC) that’s the problem in your case too. It’s an issue you probably can’t see (since the solder bridge could be under the quartz) and it is easy to verify (simply use a multimeter in continuity mode to check, if both pins of the quartz crystal are electrically connected).

[James]

What TV are you using? Not exactly the same but I’m using a DVDO unit to inject audio into HDMI with my OSSC 1.5 (until my 1.6 turns up) and I get no audio if “UHD colour” is enabled for that input.

Also I had to change one of the audio settings on the tv to get sound from my framemeister.

[nye678]

Is this the one? Not detecting any continuity on the multimeter. Is there another way to test if the crystal is bad?

The TV is a Sony KDL-26M3000. This is the model here,
https://esupport.sony.com/US/p/model-home.pl?mdl=KDL26M3000&template_id=1&region_id=1&tab=howto#/howtoTab

Also I’ve tried another TV and there is no sound with that one either.

[Morpheus_79]

Is this the one? Not detecting any continuity on the multimeter. Is there another way to test if the crystal is bad?

Yes… that’s the one. You could use an oscilloscope to check, if it delivers the 24.576 MHz needed for the PCM1862 audio A/D converter IC (U8) to work. But i would assume: the crystal isn’t bad, since those things won’t fail very often. You can check it anyway…

If there’s no problem, the tricky part begins… where you could check the power supply to the PCM1862 and its output (IF it outputs anything at all). But that’s something, i just happen to know one or two things about (in theory). Hopefully others can help…

[nye678]

There doesn’t seem to be anything coming out of the 1862. I checked pin 18 labeled DOUT according to this data sheet. Also checked the supply voltage and that looks fine, 3.3v. And there is definitely something coming in on the analog inputs.

[Goyadoy]

Hi, same issue here, but I have more information about it.
Previous I had Dell P2715Q – 4k monitor with audio out. Sound worked fine, no issues. Then I purchased Dell U2718Q – very similar monitor, but sound through HDMI not worked at all, I tested all settings in monitor and OSSC, but nothing helped.
Then I decided to try cheap HDMI to DisplayPort converter with my new monitor (HDMI-out on OSSC to DP-in on Dell U2718Q), and sound is returned! But the converter not support a lot of resolutions, so I can’t use it with OSSC as my main input.
I do not know why is this issue is happening, but hope it can addressed in future firmware updates. All another devices that I tried with the monitor don’t have any audio issues.

[nye678]

Hi Goyadoy. Interesting that between so similar a monitor the audio didn’t work. For my case none of the TVs I had access to worked with the audio over hdmi. I actually ended up sending my unit back and the new one has worked perfectly.

[Utgardaloki]

I have another similar problem that I can’t figure out. I have no audio over HDMI when running SNES in NTSC mode. Neither a supercic modded PAL machine running in NTSC mode or a supercic modded NTSC machine running in NTSC mode have any sound over HDMI. Both machines have sound in PAL mode how ever.
I’ve since updated the firmware from what the OSSC came with (can’t remember which version) to the latest 0.81-aud and same thing… no audio over HDMI in NTSC mode while PAL does.

Any ideas?

[BuckoA51]

You may need the dejitter mod for your SNES in order to get sound.

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