Left audio channel is slightly quieter using the 3.5mm jack (Av2 IN)

[LaminGaming]

Recently, I’ve noticed that the left audio channel through the 3.5mm jack (Av2 IN) on my OSSC has become slightly quieter than the right channel. I know it’s got something to do with the jack specifically as it is fine through the SCART input, so I’m not sure what’s going on with it. I did try swapping the two jack ports around with a bit of soldering, thinking that might fix it, but I got exactly the same results. So it must be something else… I even tried different cables with no luck. I do seem to recall having the issue before and it somehow fixed itself, though, I could be misremembering. Any help is greatly appreciated.

[LaminGaming]

I still can’t work out what the issue is, so I decided to get some sound recordings directly from the OSSC to share what I’m talking about:

• NORMAL.wav – Is using stock settings.

• CHANNELS SWAPPED.wav – Has only “Swap left/right” turned on.

• MONO MODE.wav – Has only “Mono mode” turned on.

https://drive.google.com/drive/folders/1RH31R0fcuK88GHWqHAbth2o4oX4zhUQO?usp=sharing

I’m thinking maybe it’s an issue with something on the OSSC’s board, a faulty resistor or cap perhaps?

Edit: I used my audio probe and found that R49 and C125 (left channel) are quieter than R51 and C123 (right channel), so maybe R49 or C125 is the culprit… I also found that switching the jack switch to Av1 OUT had no issues

• This reply was modified 6 months, 1 week ago by LaminGaming.

[LaminGaming]

I’ve replaced R49 and C125, but nothing changed. The only other thing it could be is possibly the sound chip (PCM1862).

[LaminGaming]

@marqs: Sorry to ping you, but would you happen to know what’s going on with my OSSC?

[marqs]

Sounds like PCM1862 might have been indeed damaged. Is the board v1.6 or earlier which have less protection circuitry on the analog inputs?

[LaminGaming]

Yes, it’s a v1.6 board. Thank you for letting me know that it’s most likely the PCM1862, I guess I’ll have to try replacing it with a new one at some point. However, I did have the thought of maybe trying to somehow bypass the audio input for the AV2 and use the AV3 audio input instead, as I never use VGA with anything. Though, I wasn’t sure if that was possible. Replacing the PCM1862 is probably easier.

As for why the sound issue happened in the first place, I think it’s because of the faulty Mega Drive 1 I was testing that had a missing right FM channel from the YM2612 chip. So maybe that somehow affected the OSSC.

[LaminGaming]

Also, do you have any recommendations on where to get a replacement of the PCM1862? I also live in the UK if that helps.

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