Audio noise issues – SNES Jr w/ RGB mod

[polyh3dron]

I have three RGB-modded consoles I’m using with my relatively new OSSC with HDMI out – a NESRGB-modded AV Famicom, a RGB-modded N64, and a RGB-modded SNES Jr. They’re all hooked up via SCART, using the pricier shielded SCART cables from retro_console_accessories, to my gscartsw, and then I have the gscartsw’s VGA output going to my PVM, the headphone jack output going to speakers on either side of it, and the gscartsw’s SCART output going to my OSSC which outputs via HDMI (using a Monoprice fat Redmere cable made for a long run) to a Panasonic 65VT60 plasma TV. I’m going directly to the TV from the OSSC and then using the ARC to get audio to my receiver. A pretty standard setup from what I’ve seen around here, even with a popular chart dedicated to settings for my specific TV model (none of which seem to work for me because nothing above Line2x mode gives me any signal for whatever reason).

I’m using the ARC instead of going directly to my receiver because I had it set up the other way before, but tried this as a change in an effort to get the Line4x and Line5x modes working. It didn’t help at all, and Line2x remains the only working mode for me.

With all that backstory out of the way, on to the most immediate issue I’m looking to fix: Audio noise, only coming from the SNES.

Through my aforementioned dual outputs of my gscartsw, the SNES audio going straight to my speakers from it sounds pristine. Not one bit of noise coming from it. However, the HDMI audio coming from my OSSC has a TON of noise on it. It’s definitely noticeable when in an idle menu screen, or during more sparse musical arrangements. The noise is relatively narrowband and distinctly digital in nature, and I have the OSSC’s downsampling to 48Khz turned on because I can not hear any audio at all with it turned off. This noise doesn’t occur when I am using the AV Famicom or the N64. Only the SNES. Anyone have any tips for me? I’d really like to get this OSSC working well, but so far it seems to be quite the disappointment compared to my Framemeister.

[nmalinoski]

I think this might be related to your issue: https://shmups.system11.org/viewtopic.php?p=1288693#p1288693

In a nutshell, audio problems can arise from the HDMI transmitter on the OSSC trying to digitize the weird sync timings of the NES and SNES. So far, the best fix seems to be a dejitter mod for the SNES, though I imagine routing audio around the OSSC, directly to your receiver or TV, would also solve audio issues.

[polyh3dron]

That is really unfortunate. I’m already running a long HDMI cable from my old consoles to the rest of my more modern TV setup. It’s not really practical for me to do a separate analog audio run too. I’d say that this in and of itself would be cause for me to switch back to the Framemeister, but luckily, I have a Super NT coming my way very soon, and the real SNES may end up getting retired.

[polyh3dron]

I’ll also add that there is literally zero reason for the digital audio clock for the OSSC’s analog-to-digital audio converter to be synced with the video signal, especially when there are so many consoles out there with non-standard refresh rates. IMO it’s a substantial oversight on the part of Marqs with this recent HDMI addition. It’d be nice to see a firmware update that could address this.

[marqs]

Audio ADC uses a dedicated clock – the issue is that HDMI uses a single TMDS clock which is derived from video clock, and audio is synced to that. In case of SNES that clock ends up being jittery as SNES doesn’t provide a periodic hsync, so it can cause all kinds of audio/video stability issues on receivers. You might want to keep an eye on the de-jitter mod which is currently in testing.

[polyh3dron]

Interesting update to this… I normally play SNES games using a SD2SNES. Every game I tried using, produced the noise I’m referring to. However, the Yoshi’s Island cart I just purchased plays from the same setup with ZERO NOISE.

Anyone else who has a SD2SNES, a RGB-modded SNES Jr and a OSSC with HDMI, try it out for yourself. And before anyone says it’s an issue with my SD2SNES, it sounds fine running on the same SNES with a Framemeister, and the same SD2SNES runs fine sitting in my Analogue Super Nt. Also, the sound coming out of the SNES going straight to a pair of speakers from my gscartsw sounds completely pristine. It’s only when it’s using a SD2SNES and hooked up through my OSSC that I get the noise.

[polyh3dron]

So the update to 0.80a fixed my audio issue! (and I assume the issues of many others)

Now if only I could get Line3x or 4x workin on my VT60 🙁

[b0nz0beavis]

SNES works in Lx3 on my VT60. Borti’s RGB mod installed in SNES, with OSSC connected direct to the TV.

Lx4 doesn’t work with SNES, but does with SMS,MD, Saturn and N64.

Are you stuck with Lx2 for all consoles or just SNES?

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