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Post by Talley on Feb 15, 2016 16:17:30 GMT -5
My XPA-7 was quiet in the beginning but developed a loud buzz in both the transformer and the speakers after a couple months of use. I was unable to change anything in my setup to remove the noise including buying a CMX-2 for DC noise. It was unbearable to listen to so I sent it back for service. They called me and said it had no abnormal noise with all the full load tests. My XPA-2 is dead quiet so I am unsure what the problem is with the XPA-7. Emotiva agreed to refund the XPA-7 and I am going to try the XPA-5 instead once they get a new shipment in. One point they suggested is that Panasonic plasma TVs cause a lot of line noise if you have one. Yeah. I had a panny plasma a while back and it made some of my emotiva Amps humm! Sold the panny... a year later got a samsung plasma and thought I woild give the amp a try again... this plasma also causes hum... im now selling off all plasmas I own. I need amps that do not hum. I returned both the amps also I got mine quiet... not the amp possibly your AC lines. Seems like Emotiva is just sensitive in this area possibly. |
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Post by 509Paul on Feb 15, 2016 16:28:00 GMT -5
I am curious if OLED panels have the plasma buzz characteristics or if that was only limited to the design of plasma panels.
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Post by Talley on Feb 15, 2016 16:38:25 GMT -5
I just got using REW and my Umik-1 and did an RTA and had the microphone literally stuck onto the amp and the primary frequency that was spiking was 120hz and then 240hz and again at 1khz, 2khz and 3khz.
All are harmonics off a ground loop. I need to work harder trying to eliminate mine I suppose and/or it's just the transformer fainly buzzing. The Umik picks it up better than my ears of course and it's fainly to me audible but with the mic directly on the case it can pick it up like a stethoscope picks up a heartbeat
I'll post photos later.
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Post by bigalbeco on Feb 15, 2016 20:54:02 GMT -5
I once had a ground loop problem that drove me nuts, Went so far as moving lots of electrical circuits to move all possible dimmers in the house to one leg in the circuit breaker panel. Drove another ground rod in the ground trying to isolate grounds. My Zenith projector had a power cord with a ground, subwoofer had a cord with a ground and none of the other stereo components had cords with grounds. I had a humming subwoofer and static video lines in the picture traveling from bottom to top. In the end I disconnected everything and only had the home theater preamp and projector hooked up. All I had to do is hook a ground wire to the preamp grounding lug and shove it into the grounding hole in the electrical socket and it took care of all the issues.
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Post by Talley on Feb 15, 2016 22:29:45 GMT -5
I once had a ground loop problem that drove me nuts, Went so far as moving lots of electrical circuits to move all possible dimmers in the house to one leg in the circuit breaker panel. Drove another ground rod in the ground trying to isolate grounds. My Zenith projector had a power cord with a ground, subwoofer had a cord with a ground and none of the other stereo components had cords with grounds. I had a humming subwoofer and static video lines in the picture traveling from bottom to top. In the end I disconnected everything and only had the home theater preamp and projector hooked up. All I had to do is hook a ground wire to the preamp grounding lug and shove it into the grounding hole in the electrical socket and it took care of all the issues. Ya typically a single ground wire connecting all the devices together using a large cable and then to the outlet will move any current away from signal cables and reduce this. It's a finicky situation. I'm a Master Electrician and Grounds or faulty ones can be the most problematic things to troubleshoot. |
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Post by smarties on Mar 4, 2016 9:11:43 GMT -5
I don't have Emotiva (got another amp brand) Two amps, one is a problem.
Occasional transformer hum. Quieter at night.
Sometimes pulses like a heart, or goes up and down in pitch every 40 seconds
Sometimes totally quiet, sometimes it isn't.
Mains DC blocker reduced it, but not totally removed it.
Tried plugging into a 1500VA APC UPS, amp growling away very loud. With the other amp-no noise at all.
No humm or buzz from the speakers themselves.
I had another amp from the same brand (7 chan) and a couple of channels buzzed (from the speakers) when no RCA cable was connected. No buzz when RCA cables connected.
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ilok
Minor Hero
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Post by ilok on Mar 6, 2016 10:13:38 GMT -5
SMPS doesn't have this problem  |
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Post by smarties on Mar 6, 2016 11:32:46 GMT -5
SMPS doesn't have this problem Who wants god awful class D amps for anything but the subwoofer? |
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ilok
Minor Hero
Posts: 64
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Post by ilok on Mar 6, 2016 11:42:19 GMT -5
SMPS doesn't have this problem Who wants god awful class D amps for anything but the subwoofer? I'm still trying to sell my mega buck class A amp |
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Post by 509Paul on Mar 11, 2016 15:59:06 GMT -5
Just got my XPA-5 from Emotiva that I traded for the noisy XPA-7 and it is dead quiet along with my XPA-2. Those XPA-7s must be VERY sensitive to picking up noise and buzzing.
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Post by gus4emo on Mar 11, 2016 16:39:06 GMT -5
I had a weird experience, my XPA7 was humming through all channels, I separated audio from power cables, it diminished but still there, ran 2 bare wires from preamp to amp through screws on each unit, diminished but still there, it was now only on a couple of channels and faint, lived with it for months, decided to get a CMX2, it actually got louder, and here comes the weird part, I plugged a 14 gauge 6 feet extention between the wall and the CMX2, NO HUM, NOT EVEN FAINT...I mean GONE!
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Post by 509Paul on Mar 11, 2016 16:52:34 GMT -5
I am just glad my problem with the buzzing is gone and everything is great now. I was pretty discouraged with my initial results owning the XPA-7 and XMC-1 and not even wanting to turn it on because of the noise. I still have both my amps plugged into a CMX-2 just to filter any possible noise on the power line.
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dk
Seeker Of Truth
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Post by dk on Apr 2, 2016 0:41:50 GMT -5
I am having the same issue. My XPA 7 amp is causing a constant humming noise in my speakers. I have the XPA connected to a Marantz SR5008 receiver by rca interconnects. The sound in the speakers is similar to the humming coming from the XPA 7. I have unplugged all of the components to the receiver and the panamax power conditioner to determine the cause of the noise. I tried to ground the Marantz receiver and the XPA 7 amp by attaching copper wire to a screw on each component. Please help!
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Post by nickybh on May 9, 2016 9:20:03 GMT -5
Hey everyone,
I've been following this thread as an owner of an XPA-7. I too have significant transformer hum AND Panasonic plasmas. Not sure if I'll give the CMX-2 a try. Seems interesting that a company would create a product (CMX-2) in order to solve a problem that is inherent to really only their amps. I've never heard of a DC offset issue causing transformers to hum this, then again I'm no master electrician either.
That being said, I've had several high power amps (Marantz, McIntosh, Anthem, Lexicon, Classe) through my house and not one of them have done this. My system is comprised of a Panamax Max-5100 conditioner, Marantz AV-8801, XPA-7 interconnected with AQ XLRs, and various source devices.
When troubleshooting the situation, I did notice a slight improvement when the TV is unplugged but I can still feel the vibration of the transformer. It's quite intense. Feels like a cheap Pro Audio amp from the 80s that boasts too much power for its own good. Seems like a design issue, maybe that's why it's no longer available?
I'm trying to be a fan but this experience is causing me to doubt. I will give the CMX-2 a try and see how it goes.
Any input is much appreciated.
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Post by gus4emo on May 9, 2016 11:00:00 GMT -5
Hey everyone, I've been following this thread as an owner of an XPA-7. I too have significant transformer hum AND Panasonic plasmas. Not sure if I'll give the CMX-2 a try. Seems interesting that a company would create a product (CMX-2) in order to solve a problem that is inherent to really only their amps. I've never heard of a DC offset issue causing transformers to hum this, then again I'm no master electrician either. That being said, I've had several high power amps (Marantz, McIntosh, Anthem, Lexicon, Classe) through my house and not one of them have done this. My system is comprised of a Panamax Max-5100 conditioner, Marantz AV-8801, XPA-7 interconnected with AQ XLRs, and various source devices. When troubleshooting the situation, I did notice a slight improvement when the TV is unplugged but I can still feel the vibration of the transformer. It's quite intense. Feels like a cheap Pro Audio amp from the 80s that boasts too much power for its own good. Seems like a design issue, maybe that's why it's no longer available? I'm trying to be a fan but this experience is causing me to doubt. I will give the CMX-2 a try and see how it goes. Any input is much appreciated. Hi, not sure if you read my thread, but my final try on getting rid of the hum was a "let me try this" type of thing, I plugged a 6 feet, 14 gauge extention between the wall and the CMX2, well, what do you know, hum is GONE! Of course this was after getting the CMX2 and connecting 2 wires on the chassis of both the Denon and the XPA7.... |
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KeithL
Administrator 
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Post by KeithL on May 9, 2016 11:39:04 GMT -5
A SMPS is a type of POWER SUPPLY.... and has nothing to do with whether the amplifier itself is Class D or not. While many Class D amps also use an SMPS, and most older Class A/B amps used a linear power supply.... You can have a Class D amp with a linear power supply, or a Class A/B amp with an SMPS - like our XPA Gen3. SMPS have all sorts of benefits - and there are now some quite nice sounding Class D amps out there. SMPS doesn't have this problem Who wants god awful class D amps for anything but the subwoofer? |
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KeithL
Administrator
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Post by KeithL on May 9, 2016 11:44:27 GMT -5
Most toroidal transformers are more or less sensitive to DC on the power line - and, if it's there, will often hum, and also run hotter.
However, to be honest, having a significant DC offset on your power lines isn't especially common (but, if you have it, the CMX-2 will fix it).
Hum from the speaker outputs is also commonly caused by ground loops and other ground problems.
And, aside from that, NOISE on the power line, which includes high frequency noise, and a distorted 60 Hz sine wave (which is where that 120 hz and 240 Hz comes from)
can cause the transformer itself to buzz noticeable, or leak into the other circuitry.
Unfortunately, both high frequency noise, and 60 Hz hum, are very prevalent....
Plasma TVs may both generate power line noise, and actually "broadcast" noise into the air, where it can be picked up by nearby equipment and cables.
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