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Post by gus4emo on Apr 9, 2015 12:15:09 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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Post by gus4emo on Apr 9, 2015 12:48:21 GMT -5
I meant using the Carver and XPA200 TOGETHER
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Post by vneal on Apr 9, 2015 16:18:48 GMT -5
So the problem is your sub. I take it that it is internally powered. Check your connection to the Emotiva. Make sure it is connected properly to the correct input. ONE CABLE. Ground Loops are common with sub woofers and phono pre amps. Also where is you sub plugged in? Preferably not near the amp. If so change it. I always recommend a separate outlet for the sub. I know this is not always possible. Also try a different cable to your sub.
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DYohn
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Post by DYohn on Apr 9, 2015 16:56:32 GMT -5
With nothing connected to the XPA-7 besides speakers, can you hear your hum? If so then it is simply a hum in the amp. It could be defective, it could also just be noisier than you are used to. How does it sound when playing program material?
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Post by ncred02 on Apr 9, 2015 17:16:50 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... Dont ever venture into tubes. They hum, crackle and pop
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Post by gus4emo on Apr 9, 2015 21:34:04 GMT -5
I unplug cables from the XPA7 and the hum is GONE, I plug back and the hum is back..but why there is no hum going to the sub?...the subwoofer is not internally powered, the sub is about 18 feet away, the sub amp is where it has always been, I will also try the recommendation to touch chassis with a cable from preamp to the XPA7.
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Post by rocky500 on Apr 9, 2015 21:48:42 GMT -5
Trying running an extension cable from another wall socket. Can even be from another room. Then plug each component in one by one to see if the hum goes when it is connected to this extension cable. This is a great video to watch. From around the 11 minute mark on. twit.tv/show/home-theater-geeks/139
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Post by gus4emo on Apr 9, 2015 22:12:31 GMT -5
I have one of 2 CMX6 with only the 3 amps and the preamp, will unplug the sub to see what happens, if it fixes the problem I will be glad to find where to plug it...will try that first then try other things if it does not work...
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Post by AudioHTIT on Apr 9, 2015 22:25:38 GMT -5
I unplug cables from the XPA7 and the hum is GONE, I plug back and the hum is back..but why there is no hum going to the sub?...the subwoofer is not internally powered, the sub is about 18 feet away, the sub amp is where it has always been, I will also try the recommendation to touch chassis with a cable from preamp to the XPA7. Don't focus on the sub, this test tells you that the hum is not coming from the XPA-7, at least not from its circuitry. Continue with your troubleshooting. Another question, is everything on one circuit or multiple circuits? You said you had (2) CMX-6, are they both plugged into the same circuit? You're less likely to have a ground loop if everything is on the same circuit.
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Post by gus4emo on Apr 10, 2015 11:38:21 GMT -5
Ok, the other CMX6 is in the back of the room, I have the projector and the second sub plugged there, not sure if it is the same circuit they share.
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Post by gus4emo on Apr 10, 2015 20:32:26 GMT -5
Ok, getting better, I got a cable between the chassis of the preamp and the XPA7, I got some channels with almost no hum, I mean almost dead silent, but still other channels still humming even if ever so slightly, the XPA200 I had to just lay the cable down and got those 2 channels to almost dead silent because no matter where I connected it to it was still a slight hum, the XPA7 like I said still has some channels humming, let me mention that I used an old speaker cable to do this...with the XPA7 it didn't matter what I did, some channels are still humming, is there a specific cable I should use?
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DYohn
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Post by DYohn on Apr 10, 2015 21:07:53 GMT -5
Ok, getting better, I got a cable between the chassis of the preamp and the XPA7, I got some channels with almost no hum, I mean almost dead silent, but still other channels still humming even if ever so slightly, the XPA200 I had to just lay the cable down and got those 2 channels to almost dead silent because no matter where I connected it to it was still a slight hum, the XPA7 like I said still has some channels humming, let me mention that I used an old speaker cable to do this...with the XPA7 it didn't matter what I did, some channels are still humming, is there a specific cable I should use? No what you did was right, and as has been said proves the XPA 7 is not the source of the hum. The hum is likely being caused by a ground loop between your preamp and your amp created through the RCA cables. One possible cause is the preamp (especially if it is a receiver being used as a preamp) has a three-prong power cable and the XPA-7 (being internally double shielded) does not. This creates a slight voltage imbalance between the two devices. Try a cheater plug to lift the ground off the preamp and see if that helps. Here's a cheater plug:
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Post by gus4emo on Apr 10, 2015 21:22:47 GMT -5
So I plug the preamp into this and the cable from the preamp chassis to the loop of this adapter? Or just plug the preamp to this and that's it? I keep reading about avoiding this type of adapter because it's dangerous....
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DYohn
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Post by DYohn on Apr 10, 2015 21:25:31 GMT -5
It's not dangerous. Just try plugging the preamp through one of these and get rid of the test wire. Post if it improves the situation.
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Post by gus4emo on Apr 10, 2015 21:36:08 GMT -5
Will do, thanks!
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Post by gus4emo on Apr 11, 2015 14:19:18 GMT -5
Ok DYohn, went to home depot got one of those to come home and find out that the receiver is 2 prong, lol, however I had use the side of the receiver to connect the cable and running it to the amp, then I went to the back of the receiver and connected there, seems that the hum is GONE GONE GONE, will leave like that for now, don't want to even look at it, lol, spread the word....
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DYohn
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Post by DYohn on Apr 11, 2015 14:42:32 GMT -5
The problem is in your receiver. Get a real preamp! But glad you are happy.
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Post by gus4emo on Apr 11, 2015 18:34:14 GMT -5
Now you remind about when I had the same receiver with the XPA200 and the Carver amp, using the receiver for 2 channels, no hum whatsoever, curious....
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Post by gus4emo on Apr 11, 2015 22:26:38 GMT -5
Oh No, it just came right back, I'm very frustrated....
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hemster
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Post by hemster on Apr 11, 2015 22:58:37 GMT -5
^What changed? Something has triggered it. Think of other appliances plugged into the same circuit, whether you powered on another device, etc.
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