Yet another subwoofer hum thread - AVS Forum
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post #1 of 12 Old 02-26-2013, 08:55 AM - Thread Starter
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I have tried to fix my problem using the various remedies I've found in threads on this and other sites, but to no avail.

My problem began in the usual way. We bought a new Denon AVR, replacing our pre-HDMI Pioneer Receiver. So, instead of the audio and video being split up, now they are combined through HDMI cables. We chose the Denon because it had 2 HDMI outputs and was less than $1000 and could handle FLAC files.

Because the hum was intermittent, I figured it wasn't a ground fault. I have everything plugged into an 8 year old Monster power conditioner (we're a bit out in the sticks and have some power issues). The satellite coax is also plugged into the Monster filter. Our Satellite dish is kitty corner from the "through the wall" point, exposing about 75 feet of coaxial to the elements. I think one of the sources of interference was my neighbor's industrial kitchen fan. There are also airports, submarines, and a Naval degaussing area down the road.

We had decided to upgrade to the Hopper, and we asked the tech to ground the satellite cable. This has actually made the problem worse. We are picking up sump and septic pump activity. My wife is wondering why we upgraded the receiver, especially since she thinks the video is also slightly degraded, having to pass through the AVR instead of running directly from source to plasma/projector.

Last night I was trying to read a CEDIA paper one of your members posted. I believe the point of that paper was that there are doohickeys that can isolate the subwoofer from the hum. I'm not sure I understood the paper well enough to choose a particular doohickey. My back up solution would be to run optical cable from the Hopper, since I don't think the Hopper produces any audio that optical can't handle. I'll leave the PS3 straight HDMI.

Other details. The speakers and subwoofer are AudioSonic, about 8 years old. I did have a Monster directional RCA cable, also 8 years old. I tried a new Rocketfish cable, which did not help. The plug is grounded and correct polarity. My wife has the latest Apple wifi, which is hooked up to cable.

My wife has amassed some points at Best Buy, so we might get the Geek Squad out. But I'm hoping for some ideas so we can point them in a fruitful direction.
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post #2 of 12 Old 02-26-2013, 09:36 AM
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The only thing it seems that you didn't do was to transformer isolate the cable, which is generally the most effective cure, the next most effective cure being to transformer isolate the sub interconnect. All of the money you put into anything with the Monster name on it is money down the drain, I'm afraid. BTW, ground loops aren't caused by improper grounding, they're caused by too much grounding. I'd isolate the cable first:
http://www.acousticfrontiers.com/Jensen-Transformers-Cable-TV-Isolation-Transformer-VRD-1FF.html

Isolate the sub interconnect with one of these:
http://www.amazon.com/Cables-Go-41163-Isolation-Transformer/dp/B000SO0SXC
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My wife is wondering why we upgraded the receiver, especially since she thinks the video is also slightly degraded, having to pass through the AVR instead of running directly from source to plasma/projector
I don't run my video sources through my AVR. Always thought it was a bit of an odd feature. I can only see it as useful if the TV doesn't have multiple input options.

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post #3 of 12 Old 02-26-2013, 02:36 PM - Thread Starter
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Thanks for your reply. I'm glad the doohickey you recommend is at least inexpensive. Your point about not running the video through the AVR is interesting. My wife works for a different online magazine specializing in projectors. There is much content there dealing with upconverting disc players. In that context, upconverting works. I think she hoped that the new AVR would also improve the appearance of non-HD DVD's that she likes to watch, as there are some claims made to improving video quality. Personally, I was hoping for improved audio performance so I could justify buying some Hi-Def recordings. If your theory is that the untrammeled video signal direct from source to screen is best, then I guess we should have spent the money on an amp/pre-amp like in the good old stereo days. But because we have the plasma and projector, we also liked the idea of the AVR acting as a switch instead of manually switching HDMI cables back and forth.
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post #4 of 12 Old 02-26-2013, 03:40 PM
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I've never run my video through my audio processor, IMO it adds an unnecessary element to the signal chain. If I was still running a CRT with one video input then I could see it.

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post #5 of 12 Old 02-26-2013, 04:36 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

I've never run my video through my audio processor, IMO it adds an unnecessary element to the signal chain. If I was still running a CRT with one video input then I could see it.

Interesting. How do you output audio from your source to the receiver then? There are ways of course but I am wondering how you do it.
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post #6 of 12 Old 02-26-2013, 07:20 PM
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Interesting. How do you output audio from your source to the receiver then? There are ways of course but I am wondering how you do it.
From the audio out of the TV, going through my DSP along the way.

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post #7 of 12 Old 02-26-2013, 08:01 PM
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Does your TV pass DD5.1 / DTS? What about the newer TrueHD / DTS-HD?
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post #8 of 12 Old 02-27-2013, 06:27 AM
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Does your TV pass DD5.1 / DTS? What about the newer TrueHD / DTS-HD?
Yes. The decoding still takes place in the AVR. I've compared running the audio of my blue ray direct to the AVR versus though the TV first, no difference.

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post #9 of 12 Old 02-27-2013, 09:04 AM
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Do you get the blue light on your AVR when routing audio through your TV? I would be surprised if you did. If you did then great. Some TVs don't even pass through DD let alone TrueHD and DTS-HD. If you get thd blue light you are not losing out on anything. If not and the Bluray you are watching has HD sound, then you are not getting the fullest audio available.
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post #10 of 12 Old 02-27-2013, 09:45 AM
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Originally Posted by bowmah View Post

Do you get the blue light on your AVR when routing audio through your TV? I would be surprised if you did. If you did then great. Some TVs don't even pass through DD let alone TrueHD and DTS-HD. If you get thd blue light you are not losing out on anything. If not and the Bluray you are watching has HD sound, then you are not getting the fullest audio available.
My AVR doesn't have a blue light. But if you're asking if the digital/analog source indicator indicates a digital source the answer is yes.

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post #11 of 12 Old 02-27-2013, 10:14 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

My AVR doesn't have a blue light. But if you're asking if the digital/analog source indicator indicates a digital source the answer is yes.

I see. This is the blue light that I am referring to: http://www.avsforum.com/t/863945/definitive-technology-procinema-series-600-800-1000-or-60-80-100-thread/2820#post_16199069

Most receivers with HDMI connections will have a blue light or so I thought? Could be wrong though. What receiver do you have if you don't mind me asking? I am now curious if your TV is only able to pass through DD 5.1, HD Sound or just Pro Logic OR all of the above.
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post #12 of 12 Old 02-27-2013, 11:08 AM
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What receiver do you have if you don't mind me asking? I am now curious if your TV is only able to pass through DD 5.1, HD Sound or just Pro Logic OR all of the above.
I have a Sherwood. It will decode all the above formats equally well whether I run through the TV or direct to it. I know because I've connected the blue ray through the TV to one input on the AVR, and direct to another input on the AVR, then toggled between the two. There is no audible difference.

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