PC Engine duo RGB audio hum/buzz

[deubeul]

I tried the 100uF cap thing and it din't reduce the buzz

@ Keith: Is there a groung better than the other for this? do you link all the grounds together?

[Keith Courage]

Well I can hear a drastic change if I try the cable without the cap and then hold it on there for testing. Buzzing won't go away completely but you should hear a small difference. Make sure to put the positive end on the 5V pin. Not the lower voltage end that is after the resister. I always put it here. 8+ and 4 -

[deubeul]

Thanks for the drawing effort Keith!

I was putting the cap's positive directly on the pin16 of the scart, so AFTER the resistor(I don't use pin8)

I'll do tests tonight.

[deubeul]

No change

I wired the scart the exact same way, exept I have separate L and R sound, even if I assume you too and that you used the SMS/MD shematics for illustrational purposes.

I tried with different cap values and didn't hear any difference

[thesteve]

shorten you cable or use better wire/more ground wires

[deubeul]

I'll try that but the cable is already only 1,5m long ...

[vitaflo]

I had a similar problem and bought a better cable from Retro Console Accessories on eBay.  It reduced the buzz by probably 80%.  The cable has no caps in it so it could probably be reduced further with the methods described above.

The biggest difference between the Retro Console Accessories cable and the original one I had was the shielding and grounding.  Shielding is much better and every ground point on the Scart end has a connection to ground.

One thing I found when experimenting with the noisy cable was that on my set up (briefcase), if I ran audio out from phone output on the CDROM² to the same receiver the IFU was inputting audio to, the hum/buzz was very drastically reduced.  Note, I wasn't using the CDROM for actual audio, but in essence it seems like it was most likely getting rid of a ground loop (it's the only explanation I can think of).

So if you're having issues I would do that as a test, just to see if you can minimize it that way.  It's hokey but it did work.

[csgx1]

Installed a cap in my scart plug and it seems to reduce the hum on my set up.  It's still there but definitely not as loud.  Thanks for the tip. 

[gtsamour]

This RGB buzzing is really getting into my nerves.
All of my PCEngine consoles are RGB modded (and we're talking about 7 consoles) using the classic 4 channel transistor amplifier (full cirquit), that I make myself using panasonic capacitors. The picture is just amazing, crystal clear and after the two ceramic caps fix, no jailbars at all.
I make the scart cables too using high quality scart connectors and cable (made in Germany but not with individually shielded wires).

Unless I have made some kind of mistake with the cable wiring (which I doubt after the things I read here) I really don't know what else to try except maybe the cap in the scart connector (which I will).

I bought a cable from www.retrogamingcables.co.uk for the GameCube and desides being only 1.5m (too short) the cable was really high quality and gave excellent picture and clear audio on the GC.
This guy is really trying to "hide" some components he's using to make his cables (at least the GC cable I have experience about). Using a multimeter I came to the conclusion that there has to be resistors inside the GC side of the cable in the part that can't be opened.

Anyway, I have no idea why his PCEngine RGB cable manages to eliminate the buzzing on the PCE consoles (as someone here said) but I wouldn't be surprized if there was a coil inside the male DIN connector.

Since I brought this thread back from the dead, is there any progress made that someone could share about the issue?

[thesteve]

i havent messed with it in awhile
the reason the cap works, is it makes the 5V wire another signal ground
the issue is the wire gauge used being too small in the cable allowing for voltage drop
another way to mask it would be to add an amp to the audio and drop resistors in the cable (same concept as the cables with the 75ohm resistors on video)

[gtsamour]

Well actually the cap didn't do much for me. I do hear a slight buzzing reduction but not even close to 50% at least according to my assessment. Also the cap introduces a slight ringing sound that is hardly audible but I can hear it.

I tried 100, 220, even higher capacity caps to the same end.

I'm not yet convinced that this buzzing is due to cable picking up interference and a high quality shielded cable would eliminate it. Crappy cables yes, they would make it worse.

Anyway, I ordered a triple shielded SCART to SCART cable that i will cut one end and add the DIN8 connector.
It supposedly has the following caracteristics

"Gold-plated connectors with compact plug Metallic foil shielding for protection against electromagnetic noise and interference with magnetic shielding bronzed ferrite of high purity pipes without oxygen OFC.
High precision manufacturing Using 75Ohm double aluminum foil and high density plentaz plus a ferrite is used on the cable at the end that connects to TV, for absolute rejection of EMI and RFI interference.
Robust terminals that withstand mechanical stress.
Specially constructed dielectric by maintaining the cylindrical geometry of the cable by holding the mains always aligned."

If that doesn't eliminate the buzzing, I don't know what will....

[gtsamour]

I discovered something yesterday and thought I should let everyone know....

I have a TG-16 which I have added an amp externally taking the signals from the expansion port. Attached the amp inside the removable case on the back and installed a connector on that removable casing.

The connections on the pins of the expansion port are not soldered but easily removable.

So.... I noticed the following....
If everything is connected and I disconnect the sound (L and R channel) console side, from the pins of the expansion port of the console, the buzzing is still there and even gets louder when disconnected.
Now... if i cut the sound wires (L and R) from within the scart connector this time (console side sound wires still connected), the buzzing is COMPLETELY gone, complete silence.

The test was performed by having loaded a game (Everdrive), pause it (no music or sound) and have the TV on maximum volume.

So that leads me to believe that the buzzing is caused by interference picked up by the sound carrying wires, INSIDE the cable, obviously from the RGB signal carrying wires.
External shielding will NOT solve the problem. Individually shielded wires cable (if there is such a cable I haven't seen one) WILL solve it entirely and that would be the ultimate solution.

Individual shielded pair cable for the sound (running outside the main cable) will solve it as well (but its not pretty).

Good quality cables will definitelly make it better but don't know if its possible to completely make it go away.

[Johnpv]

I get a little bit of an audio buzz/hum on just certain games.  Most the time it's minor and only noticeable if the volume is turned up a bit, except in Ys IV where its just there all the time.  Would it be worth it to get different cables for me?  Keith, you did my RGB mod on a PC Engine Duo, would the cables from the UK site that KCsims posted work on myset up as well?

[thesteve]

just a note, reducing the current in the RGB lines will reduce it notably
it will also make you pic less vivid

[Keith Courage]

I get a little bit of an audio buzz/hum on just certain games.  Most the time it's minor and only noticeable if the volume is turned up a bit, except in Ys IV where its just there all the time.  Would it be worth it to get different cables for me?  Keith, you did my RGB mod on a PC Engine Duo, would the cables from the UK site that KCsims posted work on myset up as well?

Get a cable from mckcris here in the forums. His are good quality like the ones from the UK site. They drop the audio buzz significantly. It won't be gone altogether but definitely a huge improvement over cheaper made cables. http://www.pcenginefx.com/forums/index.php?topic=18903.0

Also some devices(RGB upscalers) don't suffer from the audio buzz as much as others. So it can be different depending on the setup one has as to if a cheaper cable works okay or not.