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Post by fc911c on Dec 9, 2011 19:03:08 GMT -5
I have a hum issue as well and have noticed it especially with my rf-7's more than any other speaker i have owned but it has been present in any speaker i have tried. I have finally gotten irritated enough that this weekend i am doing a final series of troubleshooting as i have done some rather in depth ones in the past to ensure i dont have a ground loop issue. I have tested with both my rotel, marantz and HK receivers and all the speakers are dead silent so i am ruling the speakers out being defective 100%. I am hoping that the UMC-1 is not introducing noise, i dont think it is and i have all shielded emo rca interconnects and shielded HDMI cords from monoprice. My tests will consist of being isolated from from any cable tv connection. I also had my amp tested by emotiva about 6-7 or 8 months to ensure it tested out as it should and everything was in spec and the noise i had then i still have now. I have come to the conclusion, as of now, without my last round of tests that this amp is not fully refined when it comes to its noise floor. It is alot of power to have and i cannot complain about the sound quality and performance that it has given me. as i have been extremely impressed with those aspects. IMO, amps wheather low power, high power or part of a receiver, should be dead silent...like my HK and Rotel. If you know that 200 watts a channel is going to create a noise floor that is high, find a way to make it not. If my tests come out to where the amp is 100% the issue, i am going for biamping all around with amps that are around 100-125 watts a channel in the hopes that the lower channel wattages will help with lower noise floors. Unfortunately i am going with a different brand as i just have a bad taste in my mouth about this all. I do love Emotiva, they have excellent customer service, great subs, the UMC-1 has come such a long way and i love it especially comparing it agaisnt some receivers functionality. I will keep you informed as to how my tests go. thanks for the detailed report. These amps do seem problematic from what I have read here on this forum alone. One other thing you might want to know, in testing my interconnects for noise with my scope, the XPC cables didn't fair so well. My amps will be going back on Monday Frank |
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Post by roadrunner on Dec 9, 2011 19:24:36 GMT -5
SubXeRo
In previous threads about hearing noise from the XPA amps with high efficiency speakers like your Klipsch RF-7s, Lonnie has posted that the reason for this is because the XPA series amps have a gain of 32 while most amps have a gain factor in the mid 20s. He also pointed out that it has little to do with noise floor and as soon as a music signal is amplified you will not hear any distortion from your speakers.
If you want more details about this topic you can e-mail or call Emotiva and ask Lonnie or Nick to give you the full story and the steps that can be taken to minimize this noise.
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Post by wizardofoz on Dec 11, 2011 7:43:23 GMT -5
BOT...I used to have an XPA-5 that hummed but it was the torroid that hummed...and rattled the whole amp. May just have been a plac event issue but never had hum induced in the audio...since sold it but now getting a new one in the sale for some 5.1 in a new room. Hope it will be ok this time around...new house too
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alg
Seeker Of Truth
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Post by alg on Dec 11, 2011 7:48:48 GMT -5
I too have a hum or buzz coming throught two speakers from the XPA-5. The other 3 are barely audible buzz, and I have to put my ear right up against the speaker to hear it - so those 3 are basically silent, and I am happy with them. I am using Emotiva XRCA interconnect cables.
I noticed a buzz when I first plugged it in, and thought it was a mechanical vibration of the transformer, but I later tracked it down to two speakers. It is loud enough that I do hear it from my listening position during quiet parts of music, or if I play music at low volumes. It is less than a month old.
The buzz comes from woofer only, so it is a low frequency. My first thought was a ground loop but I am pretty sure I have eliminated that.
Turning up the volume on the UMC-1 has no effect on the volume of the buzz.
I unplug the cables at the amp, and it is silent. I unplug at the UMC-1 and it is silent. But I think this is a "red herring" in the logic. While plugging cables, and unplugging, I forgot to turn off the amp one time, and it went into protect mode, so it clearly "knows" when a cable is connected, and probably has some kind of muting feature when not connected?
Moving the interconnect cables has no effect on the noise. One would expect some change if the cables are picking up stray magnetic fields causing induced currents.
I swapped all the interconnect cables at the amp to one of the noisy channels. So a normally quiet channel was connected to the buzzing channel on the amp, and it buzzed. This is repeatable with all three that are silent when connected to a different channel on the amp.
I did unplug coax at the wall --- no change. Everything is plugged into the same circuit, and I tried turning lights on & off with no changes.
But to me, there are two facts that point to the source being the amp:
- moving the cables should cause some change if the cable is picking up magnetic induced current. It does not.
- swapping interconnect cable input from a silent channel should be silent on that channel, and buzz on the new channel if it was not the amp. But the buzz remains on the same channel.
Have I missed something, or does this appear to be in the XPA-5? My logic says it can be nothing else.
I have been in emails with Emotiva, and in all fairness, they have not heard the latest troubleshooting when they said it was ground loop. I am waiting until after the weekend to see what they say about the latest facts.
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Post by Telefunken_U47 on Dec 11, 2011 22:26:19 GMT -5
I had a humming problem with my XPA-5. It turned out to be the audio cabinet drawer was resonating with the transformer. I placed some rubber pads on the corners of the drawer and it was reduced to almost nothing.
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Post by mywhitenoise on Dec 14, 2011 13:41:18 GMT -5
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Post by SuBXeRo on Dec 15, 2011 21:43:00 GMT -5
here are some things i posted on another forum in regards to all this:
post 1:
i have tested. i have seen. i have lost. As a very basic test i connected all 5 of my speakers to the amp with zero rca connections to the amp, not even the cords attached. I plugged it into the wall and i got static from the tweeter and no humm/buzz from the woofers. Thats a step in the right direction. I then added my rotel to the mix, connected to the same outlet on a power strip only shared by the amp the the rotel. I then connected my L/R channel via shielded RCA, boot it all up and i have the same hum/buzz in the woofers and slight static in the speakers as i get with my UMC-1. No connections were made to my rotel aside from a rca-3.5mm jack where i used my phone to play music. I changed one of the rca cords out and it cut down on the woofer hum which is good but the tweeter is louder. I did just call emotiva and spoke to a tech and we discussed some things and he sys it is a kilowatt of power we are dealing with and high amplifier gain which are exasorbating things.
I dont know what this really tells me. Is it a ground loop? Is it an issue with the amp that when it receives a voltage it creates noise? I dont know if is hould be happy or sad.
Post 2:
Friday night i spoke with Bill, the owner of Jensen Transformers because i was looking to see what they suggested for my 5 channel setup. I was fortunate that Bills number was handed out to me as i prefer to talk to an actual engineer when it comes to issues with equipment in general. After my conversation with VInce at Emotiva about my XPA-5 hum/buzz and then having Bill explain to me more about ground loops, this is what i believe is going on. My entire setup is perfect and should not have a ground loop, so you may ask, Ian...wheres the issue then? It lies within the rca cables between the pre/pro and the power amp. Bill says that even the slighest mv droppage in voltage will cause a ground loop issue. Vince says that sometimes cords have a connection that just isnt solid enoughin the RCA cord or it gets worn and this can cause a voltage drop. Bill says that with a 6ft cord, its a length where voltage drops will begin to occur more easily.
I tested this idea out with a different RCA cord, swapping out my emo x series 6ft cord with a 6ft monoprice shielded coaxial and the hum was gone but the tweeter was a bit more staticy than with the emo cord. Its a brutal conclsion to come to that cords are this sensitive, even shielded that this makes and issues with hum buzz. I guess in a way though, it is nice to know that the amp is not the issue and i can officially rule out the XPA-5 for being "noisy" in the hum/buzz kind of way.
In the future, i am going to try and go with the shortest possible RCA cords of a quality type to prevent this last leg of the journey ground loop. Its hard when you are used to pulling components out to get to the rear of the equipment but i will just have to make it so that i can go around the furniture to access it. Overall it will be better for the equipment to not be moved and shorter runs should help to decrease the ground loop opportunities.
I hope this helps those who are battling issues like this. If not, those jensen transformer isolaters have pretty kool tech in them. They magenticaaly copy and transfer via magnetics an exact duplicate of the audio signal and have that break so the ground loop is broken. In a way, its great but you could still have bad grounds on either side of the isolater
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Deleted
Deleted Member
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Post by Deleted on Dec 17, 2011 9:40:20 GMT -5
I had a humming problem with my XPA-5. It turned out to be the audio cabinet drawer was resonating with the transformer. I placed some rubber pads on the corners of the drawer and it was reduced to almost nothing. great story. I love when fixes are this simple.  |
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Post by SuBXeRo on Dec 20, 2011 21:43:54 GMT -5
i have received my new outlaw 7125 tonight and i do not have any humm/buzz at all and i am still using the same emo x series rca's. Knock on wood this isnt just a temporary thing haha. After all this is can jusy assume that it was the amp.
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Post by w27 on Jan 23, 2012 16:38:09 GMT -5
I'm having the same hum problem with my XPA-5. I have an XPA-2 hooked up to the fronts and it's dead quiet. My extra efficient speakers don't help either. My question, since you returned the amp because of a mechanical problem not that you didn't like it... Did they cover the return shipping?
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