help me eliminate the buzzing from my SNES audio

[AndehX]

So as we all know, game consoles can have a distinct buzzing sound in the audio, especially on brightly coloured screens. Traditionally the answer to this issue has always been "use a shielded cable"

I figured it was time to fix the buzzing from my SNES. the 240p test suite is great because it has a few brightly coloured test screens and the buzzing is extremely loud. So I went ahead and bought a PACKAPUNCH RGB SCART cable from RETROGAMINGCABLES.
Here's the issue though. The new cable didn't make a difference to the audio buzzing. I even went as far as to install a 3.5mm audio jack in place of the RF jack, and connected that directly to my speakers, and the audio buzzing is still there...

So what gives? Where is the buzzing coming from? Is there a mod I don't know about that removes or reduces the buzzing? Optical SPDIF mod is a no go as I need to connect this to my capture card.

[BuckoA51]

You could go optical mod then get a DAC with pass through.

[AndehX]

Any recommendations on a DAC?

Also, I'm having issues with audio sometimes not coming out of one channel sometimes its left sometimes it's right. Sometimes it only affects sounds effects and MSU audio is fine, other times it's the entirety of the audio. Any ideas what that could be?

[AndehX]

Ok I did some probing, and found that the audio buzz is being generated in the S-MIX chip. connected a 3.5mm jack to the left and right outputs of this chip, and I can hear the buzz, even when the video cable in disconnected. The outputs of the DAC next to it do not have any buzz at all. What methods can I use to filter out this noise? Caps on the voltage input of the chip? maybe caps on the outputs? I'm all ears.

As for the audio missing from left/right channel: I've noticed if I get audio from the 2 caps before the multi-out, it sounds fine, but through my SCART cable, audio seems to randomly fade out from the left/right channel... It's not the SCART cable because I've tried 2. I've also noticed that the audio will sometimes start loud, and then fade out from 1 channel. Again this is only from the multi-out, tapping audio directly from the caps, the audio is fine. I've tried reflowing the multi-out pins.

[copy]

I don't have any concrete advice, but it reminds me of these posts I found recently while researching SNES audio chips:

https://assemblergames.com/threads/snes ... ost-830791

Perhaps the S-MIX chip has gone bad, or there's a signal problem along the audio processing path?

[AndehX]

Perhaps the S-MIX chip has gone bad, or there's a signal problem along the audio processing path?

I originally thought the same thing, but tapping audio from the capacitors right before the multi-out, it sounds fine (minus the buzzing of course)

The only time I lose sound from either the left or right channel, is through the multi-out connector. Although I can't find any issues with it.

I also tried a bypass cap on the 5v input of the S-MIX chip, it made no difference.
Tried bypass caps on the left/right outputs of the chip, and this seemingly got rid of the noise, but in the process made the audio EXTREMELY muffled. Almost like going from 44050khz audio, down to 11000khz.

[AndehX]

Ok well I worked out that having that 3.5mm jack wired up was affecting the audio going out through the multi-out. I've removed it, and everything is back to normal.
As for the audio buzz, I am stumped. When I had the 3.5mm jack wired up, I could connect that directly to my speaker system and there would be no buzzing noise, although sending audio through anything else would result in loud buzzing. Send it directly to the Line-In on my computer? Buzzing. Send it to my speaker system via my Gscart switch? Buzzing. Only when it's directly connected to my speaker system is there no buzzing at all....
It's 100% related to the RGB lines though, as disconnecting them one by one alters the volume of the buzzing. When all 3 are disconnected, there's no buzzing. I just don't understand why everything picks it up except my speaker system...

[Syntax]

You have a ground loop somewhere.

[AndehX]

You have a ground loop somewhere.

looks that way. Shame I don't have the foggiest idea where to look...

[AndehX]

Here's an example of what im dealing with: https://www.dropbox.com/s/fik2qjmwme3yk ... e.mp4?dl=0

[Syntax]

reminds me of an issue I had with my GameGear buzzing unless I lifted the ground on the headphone jack,

If your cable is fully shielded and all the grounds go to their dedicated pins there is a chance some are floating.

Quite often RGBS, common, shield and audio grounds are not linked in a scart head. Maybe this is your issue?

[rama]

Easy things to try:
Swap your devices AC plugs around, change their position and rotate them.
Ensure your PC audio input isn't configured as microphone input and that you're using the input dedicated as line-in.
Clean your console AV port (cotton swabs and alcohol), as well as your SCART equipment.
If using any other cable after the good quality SCART one, drop those and use a direct connection.

[AndehX]

I've tried all those except swapping the AC adapter. Do you mean try plugging it in somewhere else?

It confuses me because I can get clean audio, but only when I connect audio directly to my astro mixamp or my speaker system. Anywhere else and its loud buzzing

[AndehX]

Ok update: It's not my SNES that's at fault. It's something about my entire setup. Leading me to think it is actually some kind of ground loop issue. I get the same noise issues with my other consoles. I have no idea what is different now that I'm noticing the noise, compared to when I didn't notice it before... but removing the SNES completely from my setup (gscartsw, GBS scaler, VGAtoHDMI, PC etc) and connecting it to the TV downstairs, there is no noise.

What steps can I take to try and rectify a ground loop issue?

[Pikkon]

I have never used one but maybe a ground loop isolator might fix your issue.

[AndehX]

funnily enough, I actually have one, and it doesn't work. lol.

I've noticed that the actual audio is travelling through the ground signal. I can also still hear audio when just the left and right channels are connected, and no ground connection. Almost like ground is shorted into the left and right channels. If this is the case, I literally have no idea where this is happening. I've tried unplugging absolutely everything in my set up, except my SNES, and my monitor, and I still get the noise. Is it possible for my power strips to cause this kind of problem?

Also, it's worth noting that the noise im hearing is just the normal noise you'd get from the RGB signals coupling into the audio (like with cheap SCART cables) except in my setup, something is greatly amplifying this noise, or passing it back through the rest of my setup.

[rama]

Yes, your capture clearly sounds like there's a favourable ground between your TV / sound producing device and the console, that's not the audio ground return path, a "ground loop".

You need to try to guess which ground connection that could be.
In the end, all your devices are connected to the same ground at some point.
If you take a multimeter with a beep tester, you can verify that.
One of these ground paths is carrying the return currents of your audio, possibly video as well.

I lack the knowledge to tell you what exactly causes this, but it could be countless things.
Defective power strips, failing power supplies (TV, Scart solution, PC) or broken cords are all a possibility.

[AndehX]

Well, thanks for your help, but I'm honestly stumped. I'm pretty sure it has something to do with my PC as the noise only seems to be amplified when the audio is connected to my PC in some way (be it through the VGAtoHDMI, or directly through Line-In)
I've tried replacing the PC power cable and plugging it directly into the wall, and it doesn't seem to affect it. Also, I noticed that when wiggling the VGA connector going into the GBS8200, I can actually hear static coming through the audio, so something is definitely not right.
I'm about ready to give up tbh. I've exhausted every possible solution I can think of.

[Syntax]

If you can try powering the pc with a lead that does not have an earth pin.
It will probably clear the buzzing audio/loop.

Itll be the only thing in your system actually connected to the house earth I bet.

[AndehX]

If you can try powering the pc with a lead that does not have an earth pin.
It will probably clear the buzzing audio/loop.

Itll be the only thing in your system actually connected to the house earth I bet.

I could try that theoretically, but the issue is that I've already tried unplugging everything in my system except my SNES and my monitor, and I still hear the noise, so im not sure what good that would do

[crypton42]

I get the same buzzing, but only with my SD2SNES. Regular carts don't give me any audio buzz. I think this is a problem with using SD2SNES with 1Chip systems in particular, because my 2Chip SNES doesn't have this problem.
This guy did alleviated the buzz by "putting a 220uf capacitor on the 7805" https://www.retrogameboards.com/t/snes- ... zing/683/5
Have you found a better solution?