Bad audio quality through SCART from Genesis (using headphone out) – OSSC 1.6

[Zoomer88]

Hello everyone! Just got my OSCC 1.6 with audio inputs. I’m really happy about the picture quality it can provide. Hooking it up to my LG OLEDC7. Everything including Line 5x is working.

I’m using it for my region modded Sega Mega Drive (Genesis) Model 1. Only one issue is bugging me and that’s a weird sound distortion going on over HDMI. It’s as if some sort of quantization is going on since only some of the tones are being affected (especially the lower ones, like bass guitar lines in Comix Zone for example). It sounds like some sort of ringing is being added. Definitely noticeable and not very pleasant.

I’ve got a couple of TVs with SCART inputs that I’ve used before and I have no such problems with them when I connect the console directly. The setup was the same together with the same AV Receiver getting audio signal from TV through HDMI ARC.

Audio signal from the console is being routed through separate 3.5 audio jack going into SCART connector (here are the cables I’m using
http://www.ebay.co.uk/itm/SEGA-MEGADRIVE-1-GENESIS-1-RGB-SCART-TV-LEAD-WITH-STEREO-AUDIO-2-METRES/390416057480?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 ).

I’ve also tried connecting audio from the console separately routing it through OSSC’s 3.5 audio input – the result is the same. Of course no problems observed if I connect the console’s audio directly to the TV or AVR.

I’ve tried changing the “Downsampling” option in OSSC’s menu to no avail. I can’t hear any difference.

Any suggestions?

[BuckoA51]

Could this be some kind of sound processing on your AVR that only applies to HDMI?

[jonlad]

Glad this isnt just me then…

I can confirm I also have this problem on a Jap MD 1 with a Retro RGB scart into headphone jack.

Happens with optical from TV to my receiver (OSSC is direct to TV) – also happens when I have sound only routed through my TV, which removes the receiver out of the equation

Most notable on Streets of Rage 2 on the character selection screen, lots of distortion on the high end. Can also hear on the intro screen, distortion on each bass drum hit.

Also noticeable on Sonic 1.

Tried changing the downsampling option on the OSSC but this made it even worse.

I thought my speakers were busted at first but no other consoles have this issue (SFC, NeoGeoCD)

Just to make sure, I tested with headphones direct into the MD, no distortion, sounds great.

Cant be the MD or receiver.

Can this be tested by others?

[Zoomer88]

Glad I’m not the only one. Yea, I do confirm that this isn’t the receiver. The distortion could also be heard on tv’s speakers. I’ve also been able to reproduce it on my older TVs with sSCART by connecting and then removing OSSC. The distortion disappears without OSSC.

[Zoomer88]

Thinking about it – is it possible to disable audio in over SCART? Maybe it’s still active when I’m testing audio signal over separate cable? Perhaps some interference in the SCART cable is still being picked up by OSSC and mixed with clean signal from the minijack in?

Or is the SCART audio disabled when minijack is in use?

Still that does not explain why the issue is present only with OSSC. Maybe it’s sensitive to this specific interference or the interference generated by OSSC’s power supply?

[Harrumph]

I might not understand what you are doing, but I don’t think you can insert audio into the AV jack while having AV1 (scart) selected. The input only works if you are using AV2 (component). And even if you could, I don’t think this would make a difference because the audio inputs from scart and the AV1out/AV2in are connected to the same input on the audio ADC. The AV1out/AV2in switch makes sure you cannot feed to the ADC from both inputs at the same time (which one could with the 1.5 version).

[Zoomer88]

I’m getting audio over HDMI from a source plugged into terminal labeled “A1 OUT/A2 IN”. It could be a phone playing music for example. Everything’s getting mixed and send over HDMI.

Back to the issue. When I’m connecting another source to 3.5 jack and playing sound from it – there are no problems. It seems that only audio from the console affected in such a way. Could someone please test Sega Genesis with OSSC 1.6?

[Gummi]

Are you guys sure one or both of your SCART cables aren’t just poorly shielded? I would personally not trust the cable linked from eBay. Most generic cables that are not from Retrogamingcables.co.uk or Retro Console Accessories are rarely of any decent quality.
Zoomer88, is your cable from either of the two most recommended cable sellers?

I’m getting audio over HDMI from a source plugged into terminal labeled “A1 OUT/A2 IN”. It could be a phone playing music for example. Everything’s getting mixed and send over HDMI.

Someone correct me if I’m wrong, but I’m pretty sure you won’t get any sound into the HDMI stream from anything plugged into the “A1 OUT/A2 IN” port unless the OSSC source is set to component (A2). It should not inject sound into the stream from anything connected to A1. So you can’t just plug the 3.5 jack MD output straight into there if you are connecting the console via SCART.

[jonlad]

All my cables are from RetroGamingCables, incuding the MD1 scart.

I have no audio issues from any other console.

[Gummi]

I see. That is strange indeed.
I got confused by you and Zoomer btw, meant to direct the cable question at you 🙂

[jonlad]

LOL all good

It would be helpful if someone else could test by playing those two games i mentioned in my post above

[Zoomer88]

Gummi, thanks for trying to help.

Well no, my cables are not from “most recommended cable sellers”. They’re the ones I linked in my first post.

While I certainly can’t exclude the cable quality, I tend to believe this must be something else since a) I don’t get audio quality degradation when I’m not using OSSC, b) audio quality is bad even when I’m using separate high grade minijack-to-minijack cable routing audio through A1 and c) jonlad seems to have the same exact problem using what I believe is most recommended cable.

I might invest in quality cables from said sellers but it would be great if someone else test Genesis audio through scart (preferably from Model 1). I’m not really happy about paying return shipping costs for the cables and possibly for the OSSC itself if there’s no improvement/it’s a hardware bug and not fixable/works as intended etc. Genesis is the only console I bought the OSSC for.

And as I pointed out before – yes, you can plug in any other audio source to A1 and it gets mixed together with audio coming from SCART and sent over HDMI. This behavior is observed on the current (and I believe the only one for v.1.6?) firmware. I’m not sure if this was intended and might be a bug. For what I know this even might be a culprit to the issue.

Edit: now that I’m thinking about it – it might be a great feature – to be able to explicitly disable scart audio and inject audio coming from A1.

[SirRockALot]

I don’t have audio issues with my OSSC and the Mega Drive (sounds exactly as good as any other console and I couldn’t tell a difference between using the SCART input directly on my TV), but just wanted to share some general thoughts regarding cables.

– I had nothing but poor results with generic, cheap eBay/Amazon cables. They often do cause severe A/V problems. This includes everything from a Game Cube SCART cable to a Dreamcast VGA cable. Over time I replaced every single one of those with a cable manufactured by an expert (like the ones mentioned here already). Of course, upgrading the rest of your system like getting an OSSC or installing an RGB bypass on your console will only highlight the weakest link more.

Interference is a real issue. I mostly noticed two problems:

– Composite video leaks into RGB. Most cheap cables are wired for sync-on-composite instead of csync for maximum compatibility (have composite as a fallback in case the TV doesn’t do RGB, I guess). Even on consoles that have csync. Had a Neo Geo AES where checkerboard interference patterns went away the instant the cable was switched from composite to csync. PAL Game Cube (does only sync-on-composite) would show interference even with fully shielded cables because composite leaks into RGB inside the SCART switch. Sync stripper to get csync fixed it.

– Video leaks into audio. Even with the cables from RGC both SNES & Mega Drive have audio buzz / high pitched noises depending on video output. Not super noticeable, but it is there. If you hear it most during certain screens, that’s likely what that is. You can check a worst case for yourself by bringing up the grid test from the 240p test suite. You can fix this by either running audio separately or getting fully shielded cables. If you don’t hear the audio issues when you plug in headphones into the consoles but do once the audio has passed through the SCART cable alongside the video signal, that’s probably the issue.

Fully shielded cables and integrated sync strippers are quite expensive, but they’re definitively not snake oil. They can make a clear difference for audio & video.

[BuckoA51]

Sync stripper to get csync fixed it.

That makes no sense, the sync stripper lives at the SCART end of the cable, so the interference would have been added by then.

Sync strippers are not required for the OSSC and adding them just for the sake of it is not recommended, but using proper 75ohm CSYNC directly from the console can cut down on interference. Theoretically, properly shielded cables should work just as well either way (with composite, luma or csync) but that doesn’t always seem to be the case.

[jonlad]

I was able to use a 3.5mm jack from the MD headphone jack to the AV1 input on the OSSC (1.6). It plays audio when on AV1 scart.

Sound is the same as using the scart audio cable – distortion still present.

Thats the TV, receiver, MD and scart cable eliminated.

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