XPA-7 Gen 2 Interference Noise

[ngmitter]

I recently purchased a used XPA-7 Gen 2. The amp works well, except when there is no audio playing through the amplifier, I get a strange interference type of noise. It is audible from about 5-6 feet way, and does not change volume as the receiver volume knob is turned. It's still present when playing music, but easily masked by the music itself.

I've tried changing the channels on the XPA-7, but it made no difference. It's the same exact sound on my FL, FR, and C speakers, which are the only ones hooked up to the XPA-7 at this time. If I unplug the RCA interconnects from the receiver or amplifier side, the noise goes away.

The noise is NOT heard on any speakers connected directly to the receiver, a Denon x6200W. I also never experienced an issue when I had my UPA-1 and XPA-200 connected to the receiver. It's only happened on this amplifier.

I've turned off any WiFi signals in the room and removed by phone, but the noise is still present. I'm also connected to the same wall receptacle as the previous amps.

Any thoughts on what this might be? The amp is great, otherwise, but I'd like to fix this issue.

[novisnick]

May 25, 2017 8:19:37 GMT -5 ngmitter said:

I recently purchased a used XPA-7 Gen 2. The amp works well, except when there is no audio playing through the amplifier, I get a strange interference type of noise. It is audible from about 5-6 feet way, and does not change volume as the receiver volume knob is turned. It's still present when playing music, but easily masked by the music itself.

I've tried changing the channels on the XPA-7, but it made no difference. It's the same exact sound on my FL, FR, and C speakers, which are the only ones hooked up to the XPA-7 at this time. If I unplug the RCA interconnects from the receiver or amplifier side, the noise goes away.

The noise is NOT heard on any speakers connected directly to the receiver, a Denon x6200W. I also never experienced an issue when I had my UPA-1 and XPA-200 connected to the receiver. It's only happened on this amplifier.

I've turned off any WiFi signals in the room and removed by phone, but the noise is still present. I'm also connected to the same wall receptacle as the previous amps.

Any thoughts on what this might be? The amp is great, otherwise, but I'd like to fix this issue.

@keithl may better adress this but what I hear you describing is the noise floor of the amp. You should call Emotiva directly and ask for a tech. IMHO a gen 2 amp should not have an audible noise floor.



Please let us know your findings. Good Luck 

[KeithL]

The noise floor of the amp itself should be pretty close to white noise (and it's what you hear with nothing connected to the inputs).
ALL electronic circuitry makes some small amount of noise - but with our amps the noise floor should be barely audible if at all.
The fact that the noise goes away when you disconnect the inputs demonstrates that it's not the amp.

That leaves a few possibilities......

Because of the way most preamps are designed, the noise floor on the output of most preamps is fixed. Basically, if you start with the volume on the preamp all the way down, you'll hear some minimum amount of noise, which is the noise floor of the output circuitry. If you start turning up the volume, this noise floor will remain constant, then, when you reach a certain setting, it will start to rise with the volume setting. This is the point where the noise from the source, and the input circuitry on the preamp, has exceeded the noise floor of the output circuitry. The preamp's noise floor is also usually white noise (hiss)... and the amount of noise you hear from it will depend on the amount of noise the preamp outputs and the gain of the amp you've got it connected to.

Assuming that's not what you're hearing, then you're going to have to do a little detective work. Odds are that the noise is coming from the receiver itself, and simply being boosted by the amp enough that you notice it, or is coming from one of your source devices, or by the way they're connected. Since the noise level doesn't change when you change the volume setting, that means that it's "leaking in" somewhere rather than simply being part of the signal itself.  What you need to do is to start disconnecting source devices and see when the noise goes away. If it's still there with JUST the amp and the receiver connected, then it's got to be coming from the receiver itself, or the interconnects, or some sort of ground issue between them. If it goes away when you disconnect some particular source device, then you need to look in that direction. Remember that noise can get into a system through the ground connections as well as through the signal lines. (For example, it's common for noise from the ground on a computer to get in through the USB connection, even if you're listening to a different input. If that's happening, you'll usually actually notice subtle changes in the noise when the picture on the computer monitor changes - and it will probably go away when the computer is off.)
 
The way you describe the noise, as "an interference type of noise", strongly suggests something to do with the computer. The easiest way to confirm this - or not - is simply to turn the computer ENTIRELY off and see if it goes away. Since virtually all computers use a switching supply, and many of them remain partially on even when the computer is off, I would suggest actually powering the computer down and UNPLUGGING it temporarily to check this.

May 25, 2017 8:19:37 GMT -5 ngmitter said:

I recently purchased a used XPA-7 Gen 2. The amp works well, except when there is no audio playing through the amplifier, I get a strange interference type of noise. It is audible from about 5-6 feet way, and does not change volume as the receiver volume knob is turned. It's still present when playing music, but easily masked by the music itself.

I've tried changing the channels on the XPA-7, but it made no difference. It's the same exact sound on my FL, FR, and C speakers, which are the only ones hooked up to the XPA-7 at this time. If I unplug the RCA interconnects from the receiver or amplifier side, the noise goes away.

The noise is NOT heard on any speakers connected directly to the receiver, a Denon x6200W. I also never experienced an issue when I had my UPA-1 and XPA-200 connected to the receiver. It's only happened on this amplifier.

I've turned off any WiFi signals in the room and removed by phone, but the noise is still present. I'm also connected to the same wall receptacle as the previous amps.

Any thoughts on what this might be? The amp is great, otherwise, but I'd like to fix this issue.

[ngmitter]

Wow, great feedback. I'll do some experimenting tonight as you outlined. I don't recall this ever happening with the UPA-1s or the XPA-200, but perhaps I shifted some cables or changed inputs during the shift.

You may be on to something about the computer. I may have heard a slight change in pitch when the image on the monitor changed. I'll systematically unplug sources to the Denon and see what that does.

Thanks!

[novisnick]

Thanks @keithl , i knew youd have some better input.

[creimes]

I had the same sort of issue with a Sanway amp I was using on my subs, the Sanway amp had a grounded plug which the Emotiva amps don't but when I broke the ground tab off the AC cord the ground hum went away, even though I was running the amp through a CMX-2 I had to remove the ground from the plug end.

Chad

[gus4emo]

May 25, 2017 8:19:37 GMT -5 ngmitter said:

I recently purchased a used XPA-7 Gen 2. The amp works well, except when there is no audio playing through the amplifier, I get a strange interference type of noise. It is audible from about 5-6 feet way, and does not change volume as the receiver volume knob is turned. It's still present when playing music, but easily masked by the music itself.

I've tried changing the channels on the XPA-7, but it made no difference. It's the same exact sound on my FL, FR, and C speakers, which are the only ones hooked up to the XPA-7 at this time. If I unplug the RCA interconnects from the receiver or amplifier side, the noise goes away.

The noise is NOT heard on any speakers connected directly to the receiver, a Denon x6200W. I also never experienced an issue when I had my UPA-1 and XPA-200 connected to the receiver. It's only happened on this amplifier.

I've turned off any WiFi signals in the room and removed by phone, but the noise is still present. I'm also connected to the same wall receptacle as the previous amps.

Any thoughts on what this might be? The amp is great, otherwise, but I'd like to fix this issue.

I have the same amp, CMX2 didn't get rid of the hum, but most of it, had a 6 feet 12 gauge extention cord, plugged it to the wall then plugged the amp, all this after also putting a wire on 2 screws on the receiver/preamp, no human at all, it's been 2 years, knock on wood. ..

[gus4emo]

May 25, 2017 14:32:35 GMT -5 gus4emo said:

May 25, 2017 8:19:37 GMT -5 ngmitter said:

I recently purchased a used XPA-7 Gen 2. The amp works well, except when there is no audio playing through the amplifier, I get a strange interference type of noise. It is audible from about 5-6 feet way, and does not change volume as the receiver volume knob is turned. It's still present when playing music, but easily masked by the music itself.

I've tried changing the channels on the XPA-7, but it made no difference. It's the same exact sound on my FL, FR, and C speakers, which are the only ones hooked up to the XPA-7 at this time. If I unplug the RCA interconnects from the receiver or amplifier side, the noise goes away.

The noise is NOT heard on any speakers connected directly to the receiver, a Denon x6200W. I also never experienced an issue when I had my UPA-1 and XPA-200 connected to the receiver. It's only happened on this amplifier.

I've turned off any WiFi signals in the room and removed by phone, but the noise is still present. I'm also connected to the same wall receptacle as the previous amps.

Any thoughts on what this might be? The amp is great, otherwise, but I'd like to fix this issue.

I have the same amp, CMX2 didn't get rid of the hum, but most of it, had a 6 feet 12 gauge extention cord, plugged it to the wall then plugged the amp, all this after also putting a wire on 2 screws on the receiver/preamp, no human at all, it's been 2 years, knock on wood. ..

meant no hum at all

[leonski]

I'd like to reinforce what Keith said about swithcing power supplies of computers. My Plasma TV which is 100% SMPS driven will scramble my AM Radio from 50khz (well below broadcast AM lower limit) to 30mhz, which is the upper limit of my receiver. This effect is 'good' to at least 25 to 30 feet.
Turn the darn thing off and try again.

Now that I think about it, I doubt ALL the RF hash that thing produced was SMPS related.    Plenty of other RF involved in a TV which I'm certain also contributes.  

I need to repeat this test with my OLED set.    I'll do so tomorrow and add to this post.   Stay Tuned!

New TV, a 2016 LG OLED set does NOT do the same nasty stuff as my Panasonic Plasma.  AM radio is listenable even at 10 feet from the set.  

[ngmitter]

I did some testing yesterday and it's definitely the PC power supply. As soon as I turned it off, the noise went away. After I turned the power supply off, I still heard a high pitched coil whine from my case. I'm not sure if the power supply is going bad, or if it's coming from my video card. Apparently the EVGA 1080's are known for whining.

Thanks again, guys.

[leonski]

They whine when they don't get their way.

[ngmitter]

Alright, I'm bringing this thread back. I recently rearranged my setup and am having the same horrible buzzing. I thought it was my PC, but perhaps there is more to it than that.

So, I suspected it was my video card or power supply. I actually had both replaced under warranty. They gave me a new power supply (upgraded model) and a new EVGA 1080 FTW. To my avail, this made no difference. The noise is still present.

While redoing my setup and installing my 4 Atmos speaker wires, we decided to add receptacles for the wall-mounted TV and a new quad receptacle for behind the AV rack. While in there, we reterminated the ground wire and everything seemed fine. I set it up without the XPA-7 until my new rack arrived. The noise was barely noticeable.

My next test will be running an extension cord to a different circuit in the house. I'll test the PC, then I'll text the XPA-7, and see if it eliminates the hum. If so, I'll assume that the particular circuit all of my electronics are on is not grounded properly.

Fast forward to Saturday where I got my new rack. The XPA-7 went back into the mix and I'm once again getting buzzing from speakers. With the PC off, the noise is barely noticeable. With the XPA-7 removed from the chain, the noise is barely noticeable. Have both the PC on and the XPA-7 in the chain, the noise is unbearably loud. It's as clear as day from 10 feet away. It is dependent on the PC system loading, I've noticed. At desktop, it's there but quiet. When I boot up a game, the noise is immediately apparent.

Any other thoughts or suggestions? Is it possible it's the XPA-7?

The difference in volume of the noise with just the receiver vs. with the XPA-7 is exponential.

[leonski]

2 ways for generic 'interference' to get into your system.

1. Thru the air, like a radio station. Cable dress and isolation of components can help with this problem.

2. Thru cabling / interconnects / power line. This way is 'right down the pipe'. Cable TV receivers are a big deal with this, too.

The causes, of course, number in the......well, it's a potentially big number.

Can you run an extension cord TO the PC from a completely different circuit? Preferably from the other side of the box?
If the noise persists, move the PC away from the system. If the interference diminishes, it's coming thru the air. If it stays the same, it maybe coming
down the power cord.

See my post, above, where my old Plasma TV would scramble a VERY good AM radio out to 25 or 30 feet and from 50khz (long wave) all the way to the upper limits of short wave, at about 30Mhz.
Regular AM Radio is between 550Khz and 1.7Mhz, give or take. No interference noted on FM at all. This was with the radio running on Batteries, not plugged into anything.

Next steps can get ugly and a Little $$ (not huge, but an expense nonetheless). This would include going BALANCED for interconnects and trying SHIELDED power cords. An Isolation Transformer might
help, but for an amplifier? It could get $$$ since you'd need at least a 1000va device which also weighs a TON.

[ngmitter]

Well, I don't have any interference on other devices, and I'm not really close to any radio or cell antennae. However, it's always possible.

As for cable tv, I don't have any cable box in my setup. No coax connection at all.

So, as a test, I ran an extension cord to the other side of my house on the bathroom GFCI circuit, which I know is a separate circuit from my spare bedroom. When the XPA-7 was plugged into the extension cord, the noise was still there, but quieter. With the HTPC plugged into the extension cord, the noise was essentially inaudible at desktop, but I'm hearing it more out of my atmos speakers, which are run strictly off of the receiver. These are not connected through the XPA-7.

The noise is definitely quieter than before, but still present. Next, I'll try moving the receiver to another circuit....The saga continues.

[mgbpuff]

I think what you are seeing is a mismatch between tha gains of the built in Denon amps and the external Emotiva. Perhaps it could be alleviated with external resistors, but I am constantly surprised why people buy receivers and then use them as preamps. Denon gives little in the way of preamp out specs, so I am not 100% sure. But I would sell the Denon and buy an A/V prepro that is specifically designed to power various external amps.

[bolle]

I don´t think that´s the problem. I had something similar in my old system in the old house while using an UMC-200 and a PA 7-350.

For me I identified 3 sources:

1. I even had the problem (not as loud but still some buzzing) with the RCA cables connected to the amp but not to the preamp. It seemed they worked as a kind of antenna. I rerouted my cabling, separated power from signal lines and also switched to RCA - XLR cables.

2. I identified my cable line to be a problem, went from the TV over HDMI to the preamp and then to the amp. A signal filter for the cable signal helped.

3. My HTPC started to make sounds, also dependent on the load of it. I tried a lot like you and in the end built a whole new HTPC because I couldn´t fix the problem otherwise.

I also suspect you have some "dirty power" issues from SMPS in your house. This is pretty difficult to track down and fix, a real good power conditioner might help.
E.g. one of my power lan adapters breaks down for a few seconds every time a nearby led floodlight with a cheap china SMPS switches on... This gets worse and worse as more and more SMPS are used. In my experience the 7-350 was especially sensitive to this, maybe it is the same with the Gen2 amps. All of my other amps didn´t have the buzzing and other sound problems under the same conditions (AM-9080, Hypex, Pascal, Hifiakademie).

Good luck!

[LCSeminole]

A few other owners of Emotiva amps on another forum were having a similar problem with their Denon receiver/Emotiva combo and Monoprice RCA to XLR interconnects solved their problem.

[mshump]

Aug 7, 2017 17:26:20 GMT -5 ngmitter said:

Well, I don't have any interference on other devices, and I'm not really close to any radio or cell antennae. However, it's always possible.

As for cable tv, I don't have any cable box in my setup. No coax connection at all.

So, as a test, I ran an extension cord to the other side of my house on the bathroom GFCI circuit, which I know is a separate circuit from my spare bedroom. When the XPA-7 was plugged into the extension cord, the noise was still there, but quieter. With the HTPC plugged into the extension cord, the noise was essentially inaudible at desktop, but I'm hearing it more out of my atmos speakers, which are run strictly off of the receiver. These are not connected through the XPA-7.

The noise is definitely quieter than before, but still present. Next, I'll try moving the receiver to another circuit....The saga continues.

After reading this post, I'm inclined to say the problem is somewhere in either your HTPC or Receiver. With the XPA-7 in the loop its amplifying the noise on the channels.


Mark