Speaker hiss with XPA-5

[Rblaster85]

Hey all, I purchased an XPA-5 to power my home theater I was planning on running my fronts center and surrounds off of it and my rear surrounds off my reciever. I have:

RF-82ii
RC-52ii
Rs-52ii

I hooked everything up and everything sounds great, Much more powerful, the speakers sounded much better than when connected to the SR5007. My problem is that when I pause a movie or listen to 2Channel music, There is a Hiss coming from my RS-52ii which I can hear from my listening position. When I put my ear to my center and tower speakers there is a hiss as well, however I cannot hear it from my listening position. To solve this problem I just hooked the RS-52 back up to my receiver.

With all of the speakers connected to the XPA-5 the distortion issue I was having with COD black ops 2 was almost completely eliminated. However with the rear speakers hooked up to only my receiver the problem still exists.

I have also disconnected everything from the amp and just had the speakers connected, the hiss is still there so I know that its not coming from another component.


Does anyone have any suggestions on how to eliminate the hiss or is it just something I have to live with? I have a limited knowledge of electrical engineering, but I was thinking if I hooked up a resister in line with the speaker cable this would increase the resistance and make the speaker less sensitive? not sure how that would effect the components of the speaker though.

Any advice is appreciated.

 

[Steve81]

Emotiva to my knowledge doesn't recommend pairing the big XPA's with higher sensitivity loudspeakers as their voltage gain is higher than average at 32dB. However, I have heard of people getting in line attenuators over at the Klipsch forums to alleviate the problem. Barring that, return the XPA-5 and get an amplifier with lower gain. 29dB is the norm, and what Emotiva seems to be moving to with the UPA line, XPA-X00, and XPR line, and I didn't have any problems with hiss/noise pairing the XPA-200 with a pair of RF-5s.

 

[AcuDefTechGuy]

Buy an ATI amp, which is dead silent.

 

[FirstReflection]

Buy an ATI amp, which is dead silent.

Not quite DEAD silent, Acu. If I physically press my ear against my speakers' tweeters, I can make out an extremely soft hiss from my AT1805...

In actual seriousness, though, you might actually have a slightly defective amp. It's a possibility. A forum member a few months back had a similar situation with his XPA-5. Three of the channels produced a normal, very soft hiss that he could only make out from a few inches away. That's perfectly normal for most amps. But two of the channels produced an audible hiss that he could hear from his seat. That is NOT normal, and after finally getting a replacement from Emotiva, he now has a properly functioning XPA-5 that is silent at seating distance, and only produces a soft hiss that can only be heard if he's within a few inches of the speakers.

Try connecting just one speaker, and connect that one speaker to each output on your Emotiva amp. Try to discern if one or two of the channels are significantly louder than the others. If they are, then you have a couple of defective boards, and you should be firm with Emotiva until they send you a replacement.

I know that Emotiva's customer service is less than stellar sometimes. Seems to be one guy named Vincent who causes all the problems. Just ask to speak with Lonnie Vaughn and deal with him right from the get go. He'll take care of you if it really is a defective amp.

Again, a very slight hiss IS normal. But it should be very quiet or completely inaudible from your seat. And particularly if one or two channels are louder than the others. That's a sure sign of something being wrong with the amp. Talk to Lonnie and get a replacement A 100% properly functioning XPA amp is darn good, and should be very pleasing in all aspects.

 

[sgtjim]

I have an XPA-5 and I have zero hiss from any of my speakers. There are many issues that could cause a hiss, speaker cable, ground, circuit, snake in the wall so you will just have to trail and error until you remedy the issue.

 

[AcuDefTechGuy]

Not quite DEAD silent, Acu. If I physically press my ear against my speakers' tweeters, I can make out an extremely soft hiss from my AT1805...

Really?

My AT3005, AT3002, & AT2004 are absolutely dead silent with my ear pressed against the speakers and the Denon AVR master volume all the way up (w/o source playing).

I've heard from other members that the AT1800 & other models are also dead silent. But apparently not all cases then.

 

[MidnightSensi2]

Really?

My AT3005, AT3002, & AT2004 are absolutely dead silent with my ear pressed against the speakers and the Denon AVR master volume all the way up (w/o source playing).

Depends on the sensitivity of the speaker and also how the amplifier is gain staged. Yours might be gain staged properly and/or your speakers less sensitive. Usually proper gain staging is the more important of the two.

...
To OP:

I have 101/db-w speakers and have only a little hiss if I put my ears right up to them. So, we should be able to find a solution to your problem. Let's troubleshoot...

Make sure the levels out of the receiver are hot (not clipping, but, you should be watching a movie where 0 is reference level - audioholics has howtos on how to set this up). Your amp is fixed gain, so, that will allow you to turn the input attentuators down and reduce the noise of the amplifier. Since you are not powering all your speakers off similar amps, you likely will have to adjust levels a bit in the receiver. Don't worry, lowering the input attentuators does not prevent the amp from reaching full power.

 

[AcuDefTechGuy]

So the best thing to do is probably to decrease the speaker channel levels in the AVR to the reference 75dBC on the SPL meter, or just run Audyssey?

 

[ski2xblack]

So the best thing to do is probably to decrease the speaker channel levels in the AVR to the reference 75dBC on the SPL meter, or just run Audyssey?

It concerns gain and sensitivity, as mentioned above. Audyssey is another kettle of fish.

A Discussion About Idle Hiss

 

[Irvrobinson]

It concerns gain and sensitivity, as mentioned above. Audyssey is another kettle of fish.

A Discussion About Idle Hiss

Of course this dealer would say SNR is unimportant, they push vacuum tube amps. Hiss drives me nuts, I want a dead silent background if I'm buying a premium amp.

As for the Emotiva, I agree with Steve81, this is probably a component matching issue. I think Emotiva made an understandable but controversial decision to push their input sensitivity up so high. They probably did it because of weakling AVR pre-out driver circuits, but that sensitivity has all sorts of ramifications with high quality front ends. I further agree with him that line attenuators are probably a good solution; I use them with my subwoofer. Parts Express carries attenuators for balanced and single-ended cables at reasonable prices.

 

[ski2xblack]

Sorry for the smelly link, Irv, I should avoid that going forward. I was just too lazy to re-type the important parts. I think your assessment of Emotiva's design choices with the XPA series is spot on.

 

[MidnightSensi2]

I think Emotiva made an understandable but controversial decision to push their input sensitivity up so high. They probably did it because of weakling AVR pre-out driver circuits, but that sensitivity has all sorts of ramifications with high quality front ends. I further agree with him that line attenuators are probably a good solution; I use them with my subwoofer. Parts Express carries attenuators for balanced and single-ended cables at reasonable prices.

But doesn't the amp have attenuator knobs? Can just turn it down there and turn the volume up on the receiver... that's essentially the same thing as putting an inline attenuator, no?

Basically what you want to do is setup your system so the source, pre-amp/receiver and amplifier clip at all the same points. This results in the lowest noise and highest performance.

To OP:
On the receiver, when your listening with the Emotiva, where is the volume set on the receiver? -30? -20? -15? 0? +5? etc?

 

[Steve81]

But doesn't the amp have attenuator knobs?

Unfortunately no.

 

[slipperybidness]

Unfortunately no.

Nice things to have, add flexibility (and $). May not ever need them, but it is nice to have the option. It's been stated, line attenuators could be put in. Heck, you could even solder them into the existing circuitry. That's what I call "fixing factory defects".

But on a new amp, I would prefer to get gear that does the job as intended right out of the box.

 

[AcuDefTechGuy]

It concerns gain and sensitivity, as mentioned above. Audyssey is another kettle of fish.

A Discussion About Idle Hiss

Decreasing the Speaker Channel Level in the AVR is decreasing the Gain in the Preamp section, is it not?

Anyway, a loud hiss noise heard all the way from the listening position is really bad. Call Emotiva for a replacement amp free of shipping expenses or just get a new amp IMO.

 

[Irvrobinson]

Nice things to have, add flexibility (and $). May not ever need them, but it is nice to have the option. It's been stated, line attenuators could be put in. Heck, you could even solder them into the existing circuitry. That's what I call "fixing factory defects".

But on a new amp, I would prefer to get gear that does the job as intended right out of the box.

I agree, it's a design flaw most consumer amps have. On my Velodyne sub they put input level controls on the single-ended inputs but not the balanced inputs, so my pre-amp causes an overload at levels necessary to drive the ATI amp, which is why I needed discrete attenuators. The sub is designed like the Emotiva to work with low signal levels (dumb, IMO, in a $5000 sub, but most of Velodyne's subs are very mainstream products). The high-end world got obsessed with removing potentiometers from the signal path, even switches, so we're all suffering from a trend started by a line of bogus minimalist thinking.

 

[ski2xblack]

Decreasing the Speaker Channel Level in the AVR is decreasing the Gain in the Preamp, is it not?

Yes, but by doing so you get worse s/n on what goes into your amp, and the dreaded idle hiss. You want to run your AVR pre-outs as hot as possible while avoiding clipping to maximize s/n, and reel things in using the amp's gain control, if available. MidnightSensi2 put it as concisely as it gets.

 

[AcuDefTechGuy]

Yes, but by doing so you get worse s/n on what goes into your amp, and the dreaded idle hiss. You want to run your AVR pre-outs as hot as possible while avoiding clipping to maximize s/n, and reel things in using the amp's gain control, if available.

So you want to keep the preamp gain as high (hot) as possible (& avoid clipping) before going to the amp section?

That's what I like to do, but I never think about it.

I set the Speaker Channel Levels for my ATC speakers to +12.0. In fact, with the exception of my TAD & B&W (set to 0.0), all of my speakers are set from +5.0 to +12.0.

 

[ski2xblack]

Just keep in mind that you can clip your pre-amp's output, too. Clipping sounds turb wherever it occurs.

 

[AcuDefTechGuy]

Just keep in mind that you can clip your pre-amp's output, too. Clipping sounds turb wherever it occurs.

I've never heard any turbid/ muddy/ distortion noise with my settings. Definitely not a good.