A/C hum in mains and subs

[RLMe36]

Hi all,

I've been lurking for a bit and have really enjoyed the enthusiam. In my set-up I have a Panamax 5300, that then feeds my rec, amp, and sub w/amp. I have a nasty hum in all speakers, probably about 30db or so, doesn't increase with volume, but does go away when I use cheater plugs on both the amp and sub's power cord in the back of the panamax.

What usually causes this and what is the recommended fix?

Thanks,

rob

 

[zumbo]

Unplug the cable tv coax from the system/tv. Check to see if hum is gone. Then look here: http://www.hollandelectronics.com/catalog/25.pdf
Buy here: http://www.cencom94.com/gpage.html8.html

 

[warnerwh]

What you have is commonly referred to as a ground loop.

 

[RLMe36]

Thanks for the response. I was in my local audio store yesterday picking up a new cd player and was told the same thing, bought a tributary (sp?) version of below for $100, but it unfortunately doesn't solve the problem. The noise still appears with this thing inline only when I re install the cheater plugs does it go away and all I hear is an extremely slight hiss from the tweets, which I attribute to reg reciever processing noise.

any other thoughts on what it might be?

TIA,.
rob

Unplug the cable tv coax from the system/tv. Check to see if hum is gone. Then look here: http://www.hollandelectronics.com/catalog/25.pdf
Buy here: http://www.cencom94.com/gpage.html8.html

 

[kode3]

Could a bad ground in the house cause this?

 

[RLMe36]

I have a dedicated circuit that I checked yesterday and re ran the ground to a better source. No effect. It is definitely cable/coax related, though. I unplugged the in cable and still have the hum, but if I unplug the out cable for the panamax it goes away. I am thinking that I may bypass the panamax with the coax altogther, maybe that will be an improvement.

the above was done with and without the trib ground loop device too.

If anyone has another suggestion I am open to it.

thanks,

rob-with background noise

Could a bad ground in the house cause this?

 

[mtrycrafts]

I have a dedicated circuit that I checked yesterday and re ran the ground to a better source. No effect. It is definitely cable/coax related, though. I unplugged the in cable and still have the hum, but if I unplug the out cable for the panamax it goes away. I am thinking that I may bypass the panamax with the coax altogther, maybe that will be an improvement.

the above was done with and without the trib ground loop device too.

If anyone has another suggestion I am open to it.

thanks,

rob-with background noise

Yes, bypass that Panamax and see what happens. In any case, that $100 Trib needs to go back

 

[warnerwh]

Some people (EE's and electricians) may not appreciate this but leaving the cheaters on the plug won't really hurt anything and there's many of us still kicking that had no separate ground in our outlets for most of our lives. You'll notice that most toasters don't have them and they draw quite a bit of current. The third pin is only an extra or safety ground. If you have a dedicated line then you most likely have the outlets with hot and neutral properly installed. If you don't know for sure you can go to a hardware store and get a polarity checker for five bucks. Simple to use just plug it in to an outlet and see if they're correct.
It sounds like there is a ground differential between a couple of your components which is all too common. There are such things as ground breakers but the cheater plug will save the day for less money and trouble and does the job, it's that third wire causing the problem. I also ran my own lines and my amplifiers two plugs are not connected to the extra ground just for the same reason you have. It is also not a bad idea to check the house ground. Many times they are just a clamp connected to a water pipe and it's all corroded. Just clean it up, tighten it good and then cover with some silicon caulk or something similar. I'd take back the thing you paid a hundred bucks for and tell them how well it worked.

 

[RLMe36]

Some people (EE's and electricians) may not appreciate this but leaving the cheaters on the plug won't really hurt anything and there's many of us still kicking that had no separate ground in our outlets for most of our lives. You'll notice that most toasters don't have them and they draw quite a bit of current. The third pin is only an extra or safety ground. If you have a dedicated line then you most likely have the outlets with hot and neutral properly installed. If you don't know for sure you can go to a hardware store and get a polarity checker for five bucks. Simple to use just plug it in to an outlet and see if they're correct.
It sounds like there is a ground differential between a couple of your components which is all too common. There are such things as ground breakers but the cheater plug will save the day for less money and trouble and does the job, it's that third wire causing the problem. I also ran my own lines and my amplifiers two plugs are not connected to the extra ground just for the same reason you have. It is also not a bad idea to check the house ground. Many times they are just a clamp connected to a water pipe and it's all corroded. Just clean it up, tighten it good and then cover with some silicon caulk or something similar. I'd take back the thing you paid a hundred bucks for and tell them how well it worked.

Thanks, I'll take a look at the house ground. I thought of checking the polarity yesterday, it checked out fine.

That thing is definitely going back, the funny thing is, if it worked I wouldn't of cared that it cost that much to fix the problem.

Thanks again.

 

[jrohland]

Loopty-loop

Have you checked the shield on the Cable TV wire between the Panamax and the TV/Cable box? It sounds like you have some kind of ground or shield fault there.

I ran my old home theater system with a ground-lift adapter for many years. That system had pretty much the same problem you describe except, I was able to eliminate one source of hum by using a cable isolator between the outside Cable TV wire and the power conditioner. However, I had a second HUM source which required a ground-lift on one of my components.

These hum problems can be frustrating but, the ground-lift option can fix them. If your listening area is subject to standing water, a Ground Fault Circuit Interrupter between the Panamax and the electrical service might be a good idea. These can be purchased as short (pig-tail) extensions at any good hardware store.

I am not a qualified Electrician. Nor am I giving advice about how to connect electrical devices. I am only offering my own experiences in a similar situation. You should consult a qualified professional for advice.

jrohland

 

[RLMe36]

Have you checked the shield on the Cable TV wire between the Panamax and the TV/Cable box? It sounds like you have some kind of ground or shield fault there.

I ran my old home theater system with a ground-lift adapter for many years. That system had pretty much the same problem you describe except, I was able to eliminate one source of hum by using a cable isolator between the outside Cable TV wire and the power conditioner. However, I had a second HUM source which required a ground-lift on one of my components.

These hum problems can be frustrating but, the ground-lift option can fix them. If your listening area is subject to standing water, a Ground Fault Circuit Interrupter between the Panamax and the electrical service might be a good idea. These can be purchased as short (pig-tail) extensions at any good hardware store.

I am not a qualified Electrician. Nor am I giving advice about how to connect electrical devices. I am only offering my own experiences in a similar situation. You should consult a qualified professional for advice.

jrohland

I did try another method. I plugged in just the amp to another a/c source via a 10gauge ext cord which resulted in major hum then replaced the cheater plug and it went away. I even unplugged the right channel rca to see if it would have an effect, no was the answer as the hum was still there. I will say that the hum was considerable louder than when all power was coming from the panamax, so at least that thing is doing something.

You are suggesting that both the in and the out cables from the panamax may require the ground lifting device. I'll run a line from the wall directly to the tv and let you know if that works.

 

[warnerwh]

I wouldn't plug my receiver or amp into the Panamax unless it's pretty heavy duty. Another thing is to make sure no cables or interconnects lay anywhere near power cords. If they must cross them at 90 degrees or so as this will also cause noise/hum. Another thing is to see if plugging everything directly into outlets works. I had that problem with a Monster conditioner and plugged everything into outlets and the hum was gone.

 

[RLMe36]

I wouldn't plug my receiver or amp into the Panamax unless it's pretty heavy duty. Another thing is to make sure no cables or interconnects lay anywhere near power cords. If they must cross them at 90 degrees or so as this will also cause noise/hum. Another thing is to see if plugging everything directly into outlets works. I had that problem with a Monster conditioner and plugged everything into outlets and the hum was gone.

I don't know what qualifies as heavy duty, but its the model 5300 that has a delay realy specically for an amp. I also cleaned up the house ground and sealed it to slow the oxidation of the copper pipe.

The good news is that I ripped the system apart and test plugged everything on the living room floor. After plugging a piece at a time then seeing if it presented the noise. I have traced it back to the TV that is the driver, if I plug the svideo out from the rec to the tv the hum is back. If i disconnect the cable from the tv the hum goes away. So at the end it would appear that my cable tv line is infact causing the issue. I am waiting for a different loop isolater that was recommend in this post to come to see if that does it.

I now think the isolater would have worked, but I need to be in line with the TV and not just the first line that came out ( i.e. of the wall, then panamax, then Vcr, and finally tv).

 

[zumbo]

Yep. That should get it!

 

[RLMe36]

Unplug the cable tv coax from the system/tv. Check to see if hum is gone. Then look here: http://www.hollandelectronics.com/catalog/25.pdf
Buy here: http://www.cencom94.com/gpage.html8.html

Well as luck would have it Gene did an article about this very topic. I was wondering if there is a significant difference between the above solution and the Jensen transformers VRD-1FF that is mentioned in the article? I have one of the holland parts coming this week, but will get the Jensen version if need be.

Thanks,

 

[Audioholics]

Jensen is just one of the few companies posting an amplitude vs. frequency graph of their isolator and they have a very low insertion loss (-.1dB max).

 

[RLMe36]

Jensen is just one of the few companies posting an amplitude vs. frequency graph of their isolator and they have a very low insertion loss (-.1dB max).

So in other words, I should be fine with the one I choose.

 

[RLMe36]

So in other words, I should be fine with the one I choose.

Just as a follow up, I finally received my holland part for the ground loop isolation yesterday. The hum/noise is still present, but slightly louder than when using the adapters (Ugh! hands up in disgust). Now the bad part, I can't use this isolater since it cuts the resolution down so much, it actually creates a lot of snow in the picture, which leads me to believe not all are created alike, hence the reason for the recommendation for the Jensen version.

When I did the total tear down of the system the only component that introduced noise in the system was the TV. Just turning it on made noise, which I thought would be taken care of with the ground loop isolater.

Now my question is should I spring for the jensen version or is the TV some how transmitting noise to some place else?

In case anyone else thinks of it, I have just purchased a powervar 12 that will be arriving shortly. Not that i expect it to solve the ground loop problem, but it will clean up any noise in the ac lines which couldn't hurt.

rob

 

[zumbo]

Sorry it did not solve the problem. Good thing is was cheap. My Isolator did not fit tightly. I had to snug it up. Just a thought!

 

[RLMe36]

Sorry it did not solve the problem. Good thing is was cheap. My Isolator did not fit tightly. I had to snug it up. Just a thought!

Very true, so being the kind of person I am when it comes to hobbies (aka flush money away) I ordered the jensen transformer version and hope that it does the job.