VCR, not cable causing hum in amp??? (1 Viewer)

[Philip_T]

Well, I finally got my Parasound 885 and hooked it up anticipating some improved sound for my Denon2802 pushing Klipsch RF3-II's (f), RFC3-II (c), some Polk bookshelf rears and a def tech sub. I turned it on and put the hammer down. WOW! This was the sound I was hoping for all along. Much improved soundstage, background tracks aren't drowning out, cleaner, more powerful bass, etc. I was in heaven, until I went to change CD's. Then I heard the imfamous "hum" that I later found out is much documented here at HTF. After finding out that the main cause for this is the improperly grounded cable line, I rushed home after work, turned on the amp, unplugged the cable from the wall, and silence. OK, I anticipated this and had my handy grounding block, went to my cable box outside, but there was already one there. So I tightened the screws and tried again, no luck. Next, I removed the rca audio outputs from my vcr, silence. Hmmm, so I tried them in my tv audio out and the hum did not return. So my question is this, is there any way to cure the outputs from the vcr going into the Denon from humming? I currently have my cable coaxial coming from the wall into my vcr input, then coaxial out of vcr into the tv, with the rca audio out from tv to the Denon Video 1 audio input. TV doesn't sound as good, but no hum. PLII definately sounds weaker watching tv or vhs. DVD's sound fine. This is a temp fix that works for now, but I would like to run cable audio out from my vcr someday. I have the cable guy coming tomorrow to look at the cable box hookup, but it looks like that may not be the problem and I dont want to have to pay the service charge if he's not needed. Any advice would be greatly appreciated. BTW, receiver, amp, vcr, tv and sub are plugged into the same power strip, and I've been convinced not to try the ground cheater method either.

 

[Geoff S]

I don't know if this helps you, but almost always when I have my Denon 4802 (or any recevier I've used for that matter) connected to an analog source that isn't playing (the receiver's input set for that source), especially on long cable runs I get some static noise. When Digital I get no noise at all.

 

[Marvin]

Philip, I have the exact same situation as you; same amp, same hum even though there already is a cable grounding block outside. I tried a ground loop breaker: http://www.hometech.com/video/atten.html#dc
but this didn't seem to help at all. This one was only about $10 or so with the shipping so I figured it was worth a shot. I've seen other such devices on the web for $50-100.
Right now I'm using a cheater plug, which I'd like to get rid of. I'd be interested in finding out if the cable guy, or anyone else, is able to help you at all.
By the way, in my case, I get the hum/static when the receiver is set to CD and DVD, i.e. a digital source. It goes away when I set it to tape - the opposite of what Geoff found.

 

[Philip_T]

Well, the cable guy came and went and needless to say, I still have my hum. All he did was take the coax out of the vcr and plug it into the tv and said, "see, tv not making hum, its not the cable". I about went through the roof. Regardless, he spoke very little english and we couldn't understand each other, but in his infinite wisdom, he thought it was my Denon. He didnt even check the grounding outside. I pray theres no service charge for that.
Marvin, I checked all my input selections and it hums on all of em, even tape. Back to the drawing board for now. Ive heard of a 75-300-75 trick that I may try later today. I'll let you know.

 

[Wayne A. Pflughaupt]

Marvin,

Hmmm, so I tried them in my tv audio out and the hum did not return.

Were you feeding the TV’s audio into the receiver? If all you were hearing was the TV speakers, this does not prove anything since the little TV speakers will not reproduce a 60Hz hum.

There are other things to look for as well. For instance, if you sub is plugged into a different outlet from the rest of the equipment, the sub could be on a different circuit or (even worse) a different electrical phase from the other equipment. This can cause a ground loop. Try plugging the sub into the same outlet as the other gear, at least for test purposes, and see if that makes a difference.

Regards,
Wayne A. Pflughaupt

 

[Kevin Deacon]

I have the same problem with hum. I had the cable guy run the ground to the inside of the electrical panel and ground it there. This helped very little so I am now using the Rat Shack 75-300-75 trick at the expense of having ghosts on certain cable channels, but the hum is gone.

 

[Philip_T]

Wayne,
Thanks for your response and great info. I went and checked all the screws again on the grounding wire, both at the cable box and on my water main, both were hunkered down. Wire doesn't appear that old, house built in 1993. Tried your advice on removing incoming rg6 at ground loop and hum disapated a little, but was still there.
Im wondering if a ground loop isolator might help?
Regarding the tv audio, yes, I had the audio running into the receiver and the tv speakers down all the way, no hum from the amp, but poor audio quality in general (its just a cheap 27" Sanyo).
Sub is plugged into same surge protector as amp/rec/tv/vcr. Again, thanks for all your tips, its definately help my narrow it down.

Regards,
Phil

 

[Marvin]

This is probably a good indication that the problem is not with your CATV feed.

Would you then think that it's somewhere along the cable run inside my house? I had disconnected the cable from the wall in my living room and that got rid of the hum but was left with some static.
(The cheater got rid of all the noise.) Should I try putting the ground loop block somewhere else, e.g. closer to my VCR rather than where it is now?

In case it matters, the cable feed comes in to my house, then I have a splitter with half going to my cable modem and the other going to a signal booster which then goes to another splitter which feeds the signal to TVs in 2 rooms. Right now, the ground loop block is in between the signal booster and the 2nd splitter (the one that goes to 2 rooms). Do you think that's not the right location for this device?

 

[Philip_T]

Problem Solved!
Went to Rat Shak and picked up a ground-loop isolator here and ran it out from vcr audio out to receiver and blessed silence. Well, at least until I ran DMB at -15db.
Thanks for all of your input. You may want to give one of these a try Marvin. I cant say it will cure your hum, but it worked for my situation.
Regards,
Phil

 

[Marvin]

OK, thanks Philip. I'll give it a try. I had seen that before but I thought it was only for use in cars. I had thought you needed something in the cable/coax path (i.e. with RF connectors) rather than the A/V path.

 

[Wayne A. Pflughaupt]

Philip,

I had disconnected the cable from the wall in my living room and that got rid of the hum but was left with some static.

Once you get your ground lined out right, if you still have problems, then disconnect the feed from the grounding block (the cable company’s side, not the side going to the house), as I recommended for Philip

Regards,
Wayne A. Pflughaupt

 

[Vlad D]

Philip,

I also had the same problem. Same amp, same receiver. Hum was also caused by VCR. I solved the problem by just disconnecting my VCR from my receiver since I don't use it that much. But I think I'll give your solution a try.

 

[Marvin]

No, it isn’t. I certainly hope this was not installed by the cable company – they should know better. The ground block should be installed outside at the place where the service enters the house. This way the incoming signal is grounded. The way yours is set up, there is no ground for the cable modem.

Wayne,
No, that's not what I meant. There are 2 different pieces. There's a cable grounding block - that the cable company originally installed - on the outside of the house. This is connected to a wire that goes to the outside of my breaker box which is connected to the ground stake.
What I was talking about - the piece between the cable booster and splitter on the inside of my house - was the ground breaker shown here: http://www.hometech.com/video/atten.html#dc
Should I move THIS piece somewhere else in the path to my TV and VCR? Sorry for the confusion.

 

[Wayne A. Pflughaupt]

Marvin,
I’m not familiar with this device, but it probably works like the dual transformers that Kevin used. In any event, you have already said it didn’t help, so it really is moot. You might try Kevin’s trick using two 300- to 75-ohm transformers instead. I’ve also heard that one of the more expensive units, namely from Mondial (sp?), will work where the dual transformers fail.
A couple of other things:

• Try plugging the sub into the same outlet as the rest of the equipment, as I noted in the earlier post.
• Make sure no component with the cable feed attached (i.e., a cable box or VCR) is sitting directly on top of the receiver or amp.

By the way, your cable signal isn’t split many times – the booster may not be needed.
Regards,
Wayne A. Pflughaupt

 

[Marvin]

By the way, your cable signal isn’t split many times – the booster may not be needed.

You're probably right. Actually when I bought it my signal wasn't split at all. I bought it in the spirit of tweaking my system.

Anyway, I'm going to try detaching the Audio wires from my VCR to my receiver and if this takes away the hum, then I'll try that device Philip mentioned.

 

[Marvin]

Just an update in case anyone's keeping score: detaching the VCR audio wires (and also a video cable that I was using for the on-screen display) did NOT take away the hum so I guess there's no point in getting that device that worked for Philip.

Is there anything else I should try?

 

[Wayne A. Pflughaupt]

Marvin,

If I’m up to date, you still haven’t tried the back-to-back 75- to 300-ohm transformers.

Also, did you disconnect the cable company’s feed from the grounding block, as I noted in Post #5?

Regards,
Wayne A. Pflughaupt

 

[Marvin]

Wayne,
I tried that device I mentioned http://www.hometech.com/video/atten.html#dc which I assume is the same as a 75-300 transformer. Right?
No, I haven't disconnected the cable company's feed from outside so I guess I'll try that next - assuming I can (the grounding block was painted over the last time I had my house painted).
I've previously tried to tighten all the screws connecting the ground wire but wasn't able to make them any tighter.
Thanks

 

[Wayne A. Pflughaupt]

I tried that device I mentioned which I assume is the same as a 75-300 transformer. Right?

I wouldn’t assume that, because I have no idea exactly what it is.
But a look at the description should give you the answer: It says it is for blocking out infrared signals and DC power. Get the picture?
Regards,
Wayne A. Pflughaupt

 

[Marvin]

Wayne,
There are several items on that page. The one I bought and tried was the 63400 ground breaker. I think you're referring to the 20300 DC blocker.