Help! Bad Hum Part 2

[SCOOTERDOG]

My DVD player started to develop a bad hum when playing DVD Audio Disc's so I thought I might have a bad cable going on. I replaced all 6 analog cables from the player to the amp. Well this changed nothing. So I pulled the unit out and an hooked up a cheap dvd player I have using just the stereo analog outs and checked each of the 6 channel inputs on the amp and no hum. So I re-hooked up my dvd audio player and viola no hum. At this point I thought this was strange but hey maybe a ghost in the machine. So I put everything back together and dam if I didn't get the hum back.

At this point frustration is starting to set in. So I started checking the other outputs and discovered the hum is coming from the video output, both component and SVHS. When I put a movie in the player no hum because I am outputing the audio thru the optical cable.

So it seams there is a hum developing in the video output section but it only happens when I am running with the audio outputing thru the 6 analog outs. I have never had a problem like this where the video is causing hum in the audio outputs.

Thanks

Scooter

If there are any technicians here perhaps you can help me solve this. Could it be in one of the power supplies? Anyway it's been a great machine and would like to solve this without having to buy a new one. The unit is a Technics DVD A10

[Duke Spinner]

howsabout shorting the video out ...???

[SCOOTERDOG]

"howsabout shorting the video out ...???"

ummm not quite sure what you are saying...try again

[sunburnwilly]

Are you having problems like this anywhere else in the house ?

[SCOOTERDOG]

Nope no problems in any other part of the house. Like I said I tried another player and there was no hum from it. I have never had a hum problem that was related to the video output. I am using the DVD player just for my DVD Audio and CD disc and its just fine without the component or SVHS cables connected. It's pretty strange

[sunburnwilly]

Maybe you should run an individual ground to that component .

[crazytubepower]

Maybe not

[JJkizak]

One thing to check is if the cables pull out the ground shields on the player connectors. Some of them are very cheap and the new tight fitting cable connectors will actually rip out the shields. But if this hum problem has occurred over time it has to be (maybe) something internal with the player/players.

JJK

[Guest BobG]

Your problem is most likely a ground loop. You can search this forum for that topic and get some more detailed info, but I'll give you the basics here.

When you connect multiple components together, the total electrical circuit becomes complicated. Normally, there should be a single ground return path, but with multiple components this is not always the case. Especially if some of the components have three prong AC cords and also if TV cable is connected to any of the components in the system.

If this is true in your situation, then the hum is most likely caused by a ground loop rather than a faulty cable or component. Here is a way to check: if you have TV cable or a satellite dish connected to ANY component in the system, temporarily disconnect the cable. Completely. Not connected to any component in the system. Does the hum stop? If so, you need an coax antenna ground isolator like the Mondial Magic Box. (if the ground loop hum is caused by cable from your satellite dish this type of isolator will not work).

If you don't have cable or satellite connected in your system, then the ground loop is most likely from one or more system component with a 3 prong AC plug. That third prong/conductor is providing an additional path to ground and causing the hum. Eliminate that component from the system and see if the hum stops (tough to do if the component is your receiver). If so, you need an AC ground loop isolator.

Let us know the results. Many here have dealt with ground loop issues.

[SCOOTERDOG]

Bob G,

Thank you for your response. I just had a new HD Receiver installed and now that I think of it the hum started just after this. But the part that confuses me is when I removed my DVD player that was causing the hum and checked it with another DVD player of much lesser quailty and it stopped. That's what was so strange. Now I am using the Technics DVD-A10 Player for only its DVD Audio section and there is no hum. As long as I don't connect the RGB component cables or the SVHS cable to it, it is clean sounding as ever.

Is there a reason why one component would cause a hum and the other wouldn't?

My nice player is a Technics DVD-A10. Its a 22lb beast and built like a tank and the other one I used to check to see if I got hum with it is a 3lb POS Cybertron that produced no hum. I'll check on the AC ground loop isolator and see if that does it.

Thanks

Scooter

[SCOOTERDOG]

Bob G,

"(if the ground loop hum is caused by cable from your satellite dish this type of isolator will not work)."

What would I use if it is the sat cable?

Thanks

[sunburnwilly]

Hi Scooter , This is the Magic Box that Bob G wrote about .

[Guest BobG]

Satellite coax passes DC voltage to operate the LNB hung on the dish. The Mondial Magic Box and several other ground loop isolators will block the DC and cause your LNB to power down. No permanent damage, but no sat signal either. I'm sure there are ground loop isolators designed for this application but I'm not knowledgeable on that topic. Sat installer should be able to help you there.

The superior disc player hums while the el-cheapo does not. This is just a fluke and is not indicative of quality differences, just different grounding schemes in the two players. In fact, it probably indicates that the better player is working for lower hum and noise, but in your system it combines with your lash-up to provide multiple paths to ground and current flows between the various components. Ground loop does not indicate that you have a bad component, it's just a challenge to deal with in any complex system hookup.

[SCOOTERDOG]

Thanks Bob!

I was also wondering. On my last dish there was no ground wire coming from the dish to the mutiplexer, but on my new dish there is. I wondering if I disconnect it would it remove the hum. I'll try when I get back from Calif.

scooter

[Steve Donalson]

Scooter,

If a new ground was added for the sat dish that is prob. where you problem is coming from. I have dealt with ground loops many, many times. What often happens when a sat dish is installed a different grounding location is selected to ground the dish. The potential between this ground and the ground that your electrical outlets connect to is introduced into your system as a 60Hz hum. I have found by simply relocating the dish ground to the same grounding location as everything else will typically resolve this issue with a sat dish.

[SCOOTERDOG]

Thanks for the info Steve & Bob. This will be the first thing I do when I get backhome. I'll let you know if it worked.

again, Thanks!

scooter