SCART switch adds buzzing

[derFunkenstein]

I bought a Hama SCART switch (which was new in the package when I received it) and a Hama SCART cable to go my my recently-acquired OSSC.

 

My hardware:

 

TCL 55P605

OSSC

Genesis 2 VA4 with Retro-Access SCART cable

Saturn model 2 with what seems to be a SCART cable from thefoo.83 on eBay (which is a seller i picked up on here).

Dreamcast with VGA

 

I've also got some other stuff for audio and whatnot but that's not important. Eventually I'll also have an SNES with RGB when repairs are done.

 

When I hook either of my SCART-equipped systems directly to the OSSC everything is awesome. The video looks good, the audio is pure, and most importantly there's no buzz/interference. So the system and the system-specific SCART cables are good, I think.

 

When I connect even one of the systems to the Hama switch and connect to the OSSC that way, there's a buzz that's more pronounced when the image is brightly colored. It almost goes away on a totally black screen. But it's always there and it's annoying. Actually I've got two of the switches, which I accidentally bought. They both behave the same way.

 

So now I've got the task of tracking down the issue. Opinions on whether it's the switch or the cable? A different cable would certainly be cheaper than buying a different switch.

[Stephen Moss]

Can you bypass the Hama switch and connected directly to the OSSC?. That will at least eliminate the switch as the source of the problem if the buzzing is still present or implicate it if the buzzing disappears.

 

Could be a bad ground somewhere along the line allowing noise pick up in the cable or the systems themselves could be generating the noise internally and transmitting it down the cable.

 

I don't know how you have connected the power to the other systems but you could try connecting them/the Hama switch to the same power unit (if compatible) as the noiseless equipment or into the same power outlet as the noiseless equipment as that may help indicate if a ground loop is causing the noise should the noise disappear.

Edited February 26, 2018 by Stephen Moss

[derFunkenstein]

Can you bypass the Hama switch and connected directly to the OSSC?. That will at least eliminate the switch as the source of the problem if the buzzing is still present or implicate it if the buzzing disappears.

 

Could be a bad ground somewhere along the line allowing noise pick up in the cable or the systems themselves could be generating the noise internally and transmitting it down the cable.

 

I don't know how you have connected the power to the other systems but you could try connecting them/the Hama switch to the same power unit (if compatible) as the noiseless equipment or into the same power outlet as the noiseless equipment as that may help indicate if a ground loop is causing the noise should the noise disappear.

 

The Hama switch is passive, so no AC adapter to worry about (not even a port for an optional one). The SCART cable is M/M and I don't have a coupler, so I can't test it individually. I only have a method to use both the cable and the switch, or neither right now.

 

I feel like it's definitely not the individual systems, since when they're plugged into the OSSC directly there's no noise.

[marc.hull]

Ground your switch.

[derFunkenstein]

Ground your switch.

Sorry, not sure how to go about that. It's a totally passive device. The only connections are either for SCART cables or RCA outputs. Can you elaborate please? Thanks!

[marc.hull]

Sounds like ground loop bees. Touch the RCA jacks when the system is running and see if that changes the tone.

[derFunkenstein]

Sounds like ground loop bees. Touch the RCA jacks when the system is running and see if that changes the tone.

Doesn't seem to make an audible difference, but it's a familiar tone. Kinda like the buzz from a single-pickup guitar in an amp, like when the amp and guitar get too close together. If that describes a ground loop, then that must be what I have.

 

Also because I have a bunch of things on the TV stand, everything is plugged into the same Belkin power strip: https://www.amazon.com/gp/product/B000JE9LD4

 

Is the solution to get a grounded/powered switch?

[marc.hull]

No. That's grounded. Unplug the consoles you are not using and see if that eliminates the buzz.

[derFunkenstein]

No. That's grounded. Unplug the consoles you are not using and see if that eliminates the buzz.

it's a different frequency now but it's still very present.

[alex_79]

I think that's caused by the SCART cable from the switch to the OSSC, as cheap ones don't have the wires individually shielded, so the various signals cause intereferences with each other.

If you can solder or know someone that can, you can wire your own SCART cable using mini-coax cables for video and audio signals which should solve the problem. You only need an unidirectional cable for this application (just mark the connectors to know which one goes to the OSSC) and probably, you can also skip pins 8 (status and aspect ratio signaling) and 16 (composite/RGB signaling) if the OSSC doesn't need them (you'll have to check). So you'll only need 6 coax cables (R, G, B, Sync, Left Audio, Right Audio).

[derFunkenstein]

I think that's caused by the SCART cable from the switch to the OSSC, as cheap ones don't have the wires individually shielded, so the various signals cause intereferences with each other.

If you can solder or know someone that can, you can wire your own SCART cable using mini-coax cables for video and audio signals which should solve the problem. You only need an unidirectional cable for this application (just mark the connectors to know which one goes to the OSSC) and probably, you can also skip pins 8 (status and aspect ratio signaling) and 16 (composite/RGB signaling) if the OSSC doesn't need them (you'll have to check). So you'll only need 6 coax cables (R, G, B, Sync, Left Audio, Right Audio).

 

 

Yep, you're right. I bought a new SCART cable on Amazon that arrived today. This cable is kind of pricy, but it does its job perfectly. I started a return for the Hama one. My switches work perfectly without any noise, even if all three systems are turned on at the same time.

 

So this thing is solved, and I'm ecstatic.

Edited March 1, 2018 by derFunkenstein

[Zap!]

It's pricey, but I just got myself a gscartsw SCART switch. Lots of options and high build quality.