PC Engine duo RGB audio hum/buzz

[Keith Courage]

so, I've been trying to figure out a solution to the audio buzz that seems to affect all of these consoles when installing RGB. I've tried all kinds of different grounds to the scart cable, tested many different amp placements, I've tried much higher quality shielded cables, and I've even run separate audio wires from the scart cable directly to the headphone jack and still audio buzz persists.

So does everyone have a hum/buzz in their audio with RGB? Anyone out there that does not?

Wondering if this is this just a byproduct of the RGB amped signal. the same audio buzz exists with 3 different RGB amp styles that I've tested over time as well.

[thesteve]

put a cap scart end across power/ground
should reduce it

[Keith Courage]

Thanks for the advice. Added a cap and it does drop the interference down a little bit but not that much. I suppose it's better than nothing though.

[L-Digital]

This is something I have been trying to get to the bottom of for a long time. I also have this issue with my PCE and SNES. I have found out two things which leads me to believe that this is something to do with the configuration of the Scart format itself. I could be very wrong though.

Experiment 1. I use a framemeister XRGB mini. I have two different input adaptors. Scart > XRGB and JP21 > XRGB

When using a Scart setup I always get the buzzing that increases with bright screens (Konami Logo is a good test). Using the same quality JP21 configuration on the same games with the same system results in what I would estimate to be around 80% reduction in buzz.

Experiment 2
I recently did a rgb mod on a White PCE and deliberately left off the audio L and R so no sound was being channeled via the Scart lead. My plan was to use the interface phono audio out to have a nice separate clean set of audio. 
What I found was even with no audio at all connected via the Scart or the interface, I still got the buzzing sound which increased with brighter images. This astonished me considering audio was not wired up at all.

Very very strange

[thesteve]

Well normally the hum is from a shared ground, when you ran it separately if it still went to the tv then it could still be ground

Sent from my VS920 4G using Tapatalk

[L-Digital]

Keith did you manage to get this sorted? How did you wire things up?

There is a buzz on mine which I am determined to eliminate

[Keith Courage]

recently spoke with Kcsims who got a better quality cable and the hum/buzz is gone. Still wondering what makes this cable better and where to possibly get a better cable to make my own in the future.

if you don't want to try to track down a better cable you can cut down the buzzing some by adding a capacitor in between the positive and negative points in your scart cable as theSteve mentioned.

I just used a 100 uf capacitor which might even be overkill but it seem to bring the buzzing down by about half with the cables I use. positive goes to the 5 volts on the scart end and negative to one of the grounds on the Scart end.

[L-Digital]

Thanks. What rating cap are we talking?

[mickcris]

recently spoke with Kcsims who got a better quality cable and the hum/buzz is gone. Still wondering what makes this cable better and where to possibly get a better cable to make my own in the future.

if you don't want to try to track down a better cable you can cut down the buzzing some by adding a capacitor in between the positive and negative points in your scart cable as theSteve mentioned.

does their cable have individually shielded wires?

i've never really noticed it too bad with the ones i make and have also never had anyone complain about it either.  Don't think there is anything special about the ones I make though.

[Vimtoman]

Normally hum is a ground loop on audio.
If possible you need to find out what the frequency the HUM is.
If you have a scope that would help.

I fi you cant try a 220uH in series with the audio supply with maybe a 10uf  cap down to ground on the either side of the coil.

[Kcsims]

Just wanted to chime in and let everyone what cable I am using and what my setup is.

First off the cable came from:
https://www.retrogamingcables.co.uk/games-consoles/pc-engine/pc-engine-pce-duo-turbografx-16-nec-core-grafx-rgb-scart-video-av-cable

I had my system modded by KeithCourage and it was an original briefcase setup.  I run rgb through a framemeister.

Using the cable from retrogamingcables seemed to eliminate all the humming in the audio.  Not sure what the difference is in the cables are, but I had ordered all my other cables from them so I gave this one a shot too.

Hopefully this can help others out looking for a cable and those looking to modify existing cables.

If anyone has any questions, please let me know, happy to help out however I can.

[mickcris]

well there is nothing special about those cables.  i assumed you guys were talking about the slight buzzing that happens when there is a lot of white on the screen but maybe this is something else.

[Keith Courage]

well there is nothing special about those cables.  i assumed you guys were talking about the slight buzzing that happens when there is a lot of white on the screen but maybe this is something else.

Yes, but it's also noticeable when playing hu card games that have low volume. Meaning you can slightly hear the buzzing coming through even when music is playing because the music is not loud enough to drown it out. You need to listen real hard though. Then you can really hear it when music stops for a moment until it fades away. Especially in the original bomberman.

in all honesty it's not that big of a deal to me personally. I've just had others ask me about it and was wondering if anyone else who had dealt with this had found a solution.

could just flat out be that lots of people are using cheaper cables where the gauge of wire is way too thin causing some kind of audio buzz. I know generic thinly wired composite video cables do this as well so most likely the issue.

[ClodBuster]

Thank you so much for your suggestions. Both the hum as well as jailbars are so annoying when dealing with RGB.

I experienced the same hum/buzz noise when using third party RGB Scart leads for the SNES, Turbo Duo and Genesis. I found out that more often these cables do not have seperate coax shields for every video and audio signal lines. Using modified first party RGB Scart cables (e.g. for Nintendo GameCube or Xbox 360) helped, since they incorporate these coax shields.

Another possible solution would be using RCA leads for the signals, since they're coax. If they need to look neat between console A/V plug and the SCART plug, you could use thin silicone/rubber tube wrapped around the bunch of wires.

I'll also try the cap fix once I build my custom cables.

[thesteve]

as far as the freq of the hum its 60Hz, from the blanking on a white screen
the cap reduces it by half as it doubles the effective grounds in the cable