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Post by gus4emo on Apr 8, 2015 19:48:36 GMT -5
So I bought my 9 Mediabridge coax cables, again the only amps humming are the XPA7 and the XPA200, the subwoofer amp is dead silent, all using the exact same cable...although I have to put my ear on the speaker grill to hear it, it's still there....
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Post by redog on Apr 8, 2015 19:49:41 GMT -5
How often is your ear on the speaker grill?
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Post by gus4emo on Apr 8, 2015 20:02:06 GMT -5
Every time I check, there it is.
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Post by redog on Apr 8, 2015 20:03:03 GMT -5
Every time I check, there it is. Ha, well you sir need an oppo 105. Problem solved. It replaces everything but the amps. |
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hemster
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Post by hemster on Apr 8, 2015 20:08:41 GMT -5
Every time I check, there it is. The fix is easy. Resist the temptation to place your ears on the speaker grills! Listen to your music/movie from your listening/watching position instead and enjoy!  My neighbor has a new Chevy Volt and he's obsessed with the fact that it's supposed to be dead quiet. He can hear the electric motor whirring from outside the car if he's carefully and intently listening for it. But is not audible from in side the car at normal operating speeds. Told him to kick his paranoia out to the horizon in front and keep driving ahead... as if trying to catch it! |
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Post by gus4emo on Apr 8, 2015 20:32:36 GMT -5
Not trying to be smart, but would you buy an amp after the salesman tells you "by the way it comes with a hum"? Don't get me wrong I love the amps...
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Post by redog on Apr 8, 2015 20:34:17 GMT -5
Not trying to be smart, but would you buy an amp after the salesman tells you "by the way it comes with a hum"? Don't get me wrong I love the amps... what is your source? |
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DYohn
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Post by DYohn on Apr 8, 2015 20:35:26 GMT -5
Many amps hum. What's your preamp? Try this: take a piece of wire and touch one end to your preamp chassis and the other to the amp chassis. Does it stop?
By the way do you have cable TV connected to your system?
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Post by knucklehead on Apr 8, 2015 20:47:27 GMT -5
Its probably the cables - those are so good they transmit everything.
Seriously - if you have to put your ear right up to the speaker to hear the hum I don't think you have a problem. Anything that can't be heard when your butt is parked at the 'normal' listening position isn't a problem IMO.
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Post by knucklehead on Apr 8, 2015 21:46:24 GMT -5
Not trying to be smart, but would you buy an amp after the salesman tells you "by the way it comes with a hum"? Don't get me wrong I love the amps... I once had a girlfriend that came with a hum... |
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hemster
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Post by hemster on Apr 8, 2015 21:54:06 GMT -5
Not trying to be smart, but would you buy an amp after the salesman tells you "by the way it comes with a hum"? Don't get me wrong I love the amps... I once had a girlfriend that came with a hum... Presumably that's because she couldn't remember the words, right?  |
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Post by sonicseeker on Apr 8, 2015 21:56:21 GMT -5
Not trying to be smart, but would you buy an amp after the salesman tells you "by the way it comes with a hum"? Don't get me wrong I love the amps... I once had a girlfriend that came with a hum... Oh no you didn't  |
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Post by knucklehead on Apr 8, 2015 22:03:17 GMT -5
I once had a girlfriend that came with a hum... Oh no you didn't Oh yes she did! |
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Post by NotTheHerbie on Apr 9, 2015 1:09:12 GMT -5
So I bought my 9 Mediabridge coax cables, again the only amps humming are the XPA7 and the XPA200, the subwoofer amp is dead silent, all using the exact same cable...although I have to put my ear on the speaker grill to hear it, it's still there.... gus4emotiva, I recently upgraded from an XPA-3 to an XPA-7 as part of transforming my living room into my new home theater. In parallel with swapping in the XPA-7, I added an Oppo BDP-103 and Comcast Xfinity X1 cable box. To my horror, when I powered everything up for the first time, I discovered I had gained a very audible 60Hz hum and I could occasionally hear mechanical transformer hum coming from the XPA-7. Prior to installing my new configuration, I had purchased an XMC-1 which drove the XPA-3 . . . and everything was dead silent! After doing some research online and performing a few experiments, I discovered the source of the 60Hz hum was my cable TV cable connected to the Xfinity X1. If I disconnected the HDMI cable running from the X1 to the XMC-1, the 60 Hz hum went away. Same thing if I disconnected the cable TV coax from the Xfinity X1. To solve this problem, I purchased a "coaxial isolator" made by Tii Technologies. It is their model# TII 220. From their website, "The 220 Coaxial Isolator provides galvanic isolation both the shield and center conductors of a standard 75 ohms coaxial system while maintaining low insertion loss for RF signals. The Isolator eliminates ground loops, and provides a degree of protection for electronic equipment from electrical transients and inadvertently “Hot” coax shield or center conductors." I bought it on Amazon.com for about $20 and looks similar to below.  Please note that you need to insert this isolator prior to the cable TV coax "touching" any part of your system. If you insert it after passing through a conventional surge suppressor, you may contaminate every device attached to that surge suppressor. For my installation, I have the cable TV coax attached to the TII 220 which is then attached to my Furman Elite DM 15i coax surge suppressor. You could also attach the TII 220 directly to your cable box coax in. This completely eliminated the 60Hz hum. However, it did not eliminate the transformer hum that I discovered could also be heard through the speakers (now that the 60Hz hum was gone.) The transformer hum was a more curious problem as it would randomly come and go. Sometimes my system would be dead quiet and sometimes I could hear the mechanical transformer hum (from the XPA-7 itself) with the volume turned all the way down. Searching online I found a lot of information (and misinformation), but I also found a research paper that discussed transformer hum and its causes and tried to identify the significant causes. It concluded that one of the significant contributors to transformer hum was DC offsets on the AC power lines. Even rather small DC offsets were shown to cause audible hum. DC offsets on normal household AC can come from anywhere, from cheap wall wart DC power supplies to hairdryers and other appliances. Disturbances to AC power from neighboring homes and businesses can also make it into your home. Since this could explain the random nature of what I was hearing, I decided to try to eliminate any DC offsets from the AC power supplying the XPA-7 and see (hear) what happened. To address this, I purchased an Emotiva CMX-2 and inserted it between my Furman surge suppressor and the XPA-7. From Emotiva's website, "The CMX-2 offers a solution to a less-familiar, common problem - DC offset on the AC power line. DC offset is usually the result of unbalanced loads or by flaws in the power distribution system itself. It can cause DC current flow in the transformers that power your audio equipment, making them run hotter, produce more mechanical hum, and, in extreme cases, even potentially causing permanent damage. In addition to removing line noise, the CMX-2 also totally eliminates this annoying and potentially damaging problem as well." I am happy to report that since adding the CMX-2, the transformer hum from my XPA-7 has disappeared. My system is back to being dead silent (except for when it's pumping out glorious tunes or dynamic movie sound tracks.) My theory regarding the difference in behavior between the XPA-3 and XPA-7 is that the XPA-7 (or at least my XPA-7) is simply more sensitive to bad AC power than the XPA-3 is. I hope this helps. - Mike |
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Post by boomzilla on Apr 9, 2015 5:36:47 GMT -5
Hi gus4emoI've not experienced hum with my solid-state electronics, but I have had some tube components that were highly sensitive to power conditioners. I think that DYohn's advice is the first step to try, but should it not work, consider unplugging from your power-conditioner / surge-suppressor and try the components plugged directly into the wall. Just a thought... Boom |
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Post by vneal on Apr 9, 2015 7:20:29 GMT -5
Unplug each source one by one. If you have a PHONO PRE AMP my bet is it is that. If so relocate the plug or get a better Phono pre amp ( I did)
No PHONO PRE AMP? and you have checked each sources? Then it is probably your cables. REPLACE
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Post by vcautokid on Apr 9, 2015 8:22:17 GMT -5
A great question was asked in a previous post. What is the system compliment, Preamplifier,speakers etc. Any provider decoders, i.e. cable, satellite, etc. Troubleshooting with out all the components, and details is like trying to judge a beauty contest over the radio.
The way I troubleshoot by the way is component isolation, and elimination. Also the basics, AC power lines away from signal lines, or they run perpendicular to them. The Coax galvanic Isolator is a top tip if you DO have provider services that are always suspect for hum, and noise. My Charter service was real bad.
Some noise heard from directly the speaker is normal to a degree. If you hear it from your listening position, many feet away, then not so much normal.
More often than not, in hum, it is not always the exotic solution that gets it, it is many times the basics. Right down to a marginally bad cable, and so on.
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Post by AudioHTIT on Apr 9, 2015 8:56:36 GMT -5
In your original thread you jumped to the assumption that your subwoofer didn't hum because of the type of cable that connected it, the conclusion was to buy more of that type cable. As others have mentioned you have to do proper troubleshooting. I don't remember if you've ever disconnected all the inputs to the amp and reported results? I'd start at the amp and work back toward the source, but any method that isolates a single component at a time will work.
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jlamo
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Post by jlamo on Apr 9, 2015 11:55:29 GMT -5
I had a hum issue with my rythmik sub and a Nad receiver at the same time. I removed the nad and swapped with another receiver temporarily and the hum was in the sub but not the replacement receiver . So I thought maybe both the first receiver and sub just had this issue but after much trial and error I found that my laptop charger was the issue . I checked to see if it were on the same breaker as the equipment but it wasn't . I replaced the laptop charger and put the first reciever back and all was good. After I solved the issue and all was working good I continued to play around with the bad charger and plugged it in different outlets around the house and it always caused that hum. All because one amplifier doesn't cause a hum and another one does is not evidence that the second amp is bad or defective. Good luck.
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Post by gus4emo on Apr 9, 2015 12:14:59 GMT -5
I want to thank all of you for your replies, ok, I unpluged the cable going from the wall to the cable box, I even unpluged the cable box, the preamp is not on, still humming, I unplug a cable that goes from the preamp (which by the way it is a Denon 4520 being used as a preamp) and goes to the XPA7 then plug it into the sub amp (NHT), hum not there, plug back to the XPA7 hum is there.......maybe I should mention that before I hooked the XPA7 to the system I was using and still use my XPA200 and a Carver THX certified 5 channel amp, no hum at all, there was a slight hum I detected from the subwoofer, but gone after changing that cable to the Mediabridge, when I ordered the XPA7 also ordered Monster 400 THX cables for all 9 channels, then recently bought the Mediabridge cables since the one for the sub did not pick up anything (and I got the exact same one)........I was using less quality cables when I used the Carver and XPA7 together with same sub, no hum, and by the way the sub was humming a bit because I had to use an extension cable then, and again is gone after using the Mediabridge, this weekend I will keep trying to eliminate the hum following some advice from you guys, I will resist buying anything until I have tried everything.......I already have tried a couple of things as you can see on this thread.........I really love my Emotiva amps, but that freaking hum has to go........
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