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Post by sahmen on Oct 27, 2017 20:13:13 GMT -5
For about a month or two now, I have been noticing a certain lop-sidedness in the sound-scape produced by the 2 XPA-1 Gen-2 monoblocks deployed as fronts in my main 2-channel system. The left channel seemed to sound more energetic in several ways than the right channel, even though I have not tweaked or EQ'ed the balance on my XMC-1 to produce any such lop-sidedness.
The imbalance was particularly palpable from my favorite listening spot, which is about 14ft away from my rig. I also noticed that the indicator lights on the XPA-1 driving the left channel was more lively and active than the lights on the XPA-1 driving the right channel speaker, although I do not remember noticing that discrepancy until very recently, when I started noticing the channel imbalance. No, the signal on the right channel is not dead, but I have to go near the speaker on the right in order to hear it.
Additionally, while the indicator lights on that right channel XPA-1 remained active, the extent of their liveliness and their general strength had diminished a lot lately, so that for every 8-12 steps (or dots) that the lights on the left channel moved to the right during playback, the lights on the right channel would only move 1-3 steps, that is if they move at all.
With all that said, because the right channel seemed to be working, and was not entirely dead, I have been blaming everything else in my set up, except the amps, in an attempt to explain the imbalance I have been hearing to myself: At times, I thought maybe my Roon DSP engine had developed some kind of glitch in its configuration (although it was difficult to see why, since I never really mess with it)...
Sometimes I thought it was my Yggy, even though it just returned from S.chiit where I sent for a USB Gen 5 board installation and (hopefully) general maintenance... Sometimes too, I thought it was the fault of my right channel PSA sub, which needs some maintenance... Sometimes too, I blamed my own hearing, suspecting that I was probably going deaf in my right ear, although nothing in my normal hearing activities (outside 2-channel audio listening) has been giving me the slightest cause for concern lately. Frankly I have found all these explanations to be, to some extent, head scratchers, and didn't really know what to think about the channel imbalance problem until I replaced the monoblocks today with an idle Emotiva SA-250 which I have been meaning to test-drive in my 2 channel system for several months now...
As soon as I fired up the SA-250 and took a seat in my favorite listening spot, everything became perfectly aligned again in the sound-scape, and the apparent channel imbalance suddenly went "bye-bye." That swap is what confirmed to me that the right channel XPA-1 was not firing on all cylinders, and it is what made me call Emotiva today to report my problem... The right Channel XPA-1 is now back in the box and ready to be RMA'ed to Emo at Franklin for a maintenance visit, which will hopefully solve the problem.
Still I am curious about what could have happened to my unit? I have never witnessed a situation in which the signal strength of an amp can become this weak even when the amp appears, on the outside, to be working normally. Is this a familiar problem with amps? Has anyone experienced something like this before?
Any insights, however tentative?
Thanks in advance.
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Post by leonski on Oct 27, 2017 23:21:32 GMT -5
Strictly GUESSING: Bias. Went badly out of adjustment. Does the amp idle a LOT cooler than its twin? Output Devices. Amp has several pair. One pair going open or more than 1 pair dead? Might cause what you hear? Some part of the circuit which separates the normal and inverted part of the signal might be bad, but I don't know what kind of audible effect that would have. By substituting another known good amp, you took the speakers, input and all wriing out of the equation. Good. You are doing the right thing by sending it back to the 'pros' emo. Please post back when you have a resolution to 'root cause'. |
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Post by garbulky on Oct 28, 2017 0:31:32 GMT -5
Weird story but it worked for me. Try changing the XLR interconnects.
Also there was a issue where a gungnir multibit I used caused chanel imbalance - which ...was intermitten. Sometimes it was there, sometimes it wasn't.
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Post by AudioHTIT on Oct 28, 2017 0:38:37 GMT -5
I might have swapped amp channels first, just to hear the problem go to the other side, but you made it go away so that works too. ... you know, if you had a measurement on idle power, that might tell you something about bias. You should probably measure both of them when you get it back, and then post in the measurements thread. You could do the SA-250 too!  |
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Post by mfeust on Oct 28, 2017 9:49:17 GMT -5
I might have swapped amp channels first, just to hear the problem go to the other side, but you made it go away so that works too. ... you know, if you had a measurement on idle power, that might tell you something about bias. You should probably measure both of them when you get it back, and then post in the measurements thread. You could do the SA-250 too! +1 I too was going to suggest switch the right amp to the left channel to see if it follows that amp. I would do this before sending it in to Emotiva just for peace of mind. Inquiring minds want to know. Mark |
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Post by sahmen on Oct 28, 2017 11:49:28 GMT -5
Now that some of you guys mention it, I wish I had swapped the cables on the L/R XPA-1s to see if the problem would move to the other end. Yet, installing the Sa-250 has made such a big difference in restoring balance that it leaves no doubt in my mind that the right channel XPA-1, whose indicator lights were barely moving during playback, was the culprit...
One thing I have not mentioned is that it is the Technical Support guy at Emo whom I spoke to who suggested the immediate RMA after I described the problem and circumstances to him in the same way I have here. I was expecting him to have me go through I few troubleshooting steps first, as they usually do... But when I explained how consistent the problem of the weakened signal in the right channel had become lately, he simply instructed me to return the unt, so I obeyed...
Gar: I am also familiar with occasional, intermittent manifestations of imbalance, but in my case I have always considered that to be source dependent. The Yggy is quite adept at placing the sounds of certain instruments in specific positions in the wide and deep soundstage it normally generates. It is not uncommon to hear the sound of a record dominated by piano-music weighted to one side of the soundstage whenever the piano is prominent over the sounds of other instruments. However, in such cases, the balance can shift when the sounds of other instruments (say cymbals, kick-drums, saxophones, trumpets, or upright bass) regain prominence.
Also, in such cases, intermittent and alternating left/right channel (over)emphasis, where they occur, change and shift back and forth depending on the source, and those patterns are consistent to the point where, for albums I listen to frequently, I know where to expect the sound of certain instruments to come from, within the soundstage, and have a sense of how far from me each instrument seems to be placed. The case I am reporting is, on the other hand, one in which all such signal emphasis had become consistently weighted to the left-side of the soundstage for more than a month.
AudioTIT: I'd gladly take the measurements on idle power you have mentioned, when I have the outgoing XPA-1 back in play, but could you let me know what tool I might need for that?
Incidentally, I have gained a lot of respect for the SA-250 because of the awesome job it is doing filling the shoes of of the 2 XPA-1 Gen 2s. When all chips are down, I prefer to have the two monoblocks in this system, because I do notice certain subtle differences in performance that were making me miss the XPA-1s yesterday. However, listening to the SA-250 again today, I can say that it is doing such a capable job covering for them that I am not going to miss them too much, although I am still eager to get the RMA'ed unit back and find out what exactly went awry with it.
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Post by leonski on Oct 28, 2017 12:02:37 GMT -5
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Post by AudioHTIT on Oct 28, 2017 12:05:56 GMT -5
AudioHTIT: I'd gladly take the measurements on idle power you have mentioned, when I have the outgoing XPA-1 back in play, but could you let me know what tool I might need for that? Here’s a thread I started for measurements, it also describes taking measurements with a Kill-O-Watt meter, if you don’t have one they’re about $20 on Amazon. Hope your repair goes well, once it’s back you could measure both XPA-1’s just to have a baseline on each, and the SA-250 to help us complete the Emotiva measurements. emotivalounge.proboards.com/post/911602/thread |
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klinemj
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Post by klinemj on Oct 28, 2017 12:19:54 GMT -5
Sounds to me like a classic case of cable-lifter imbalance. If the one side's power cable is lower than all the others', it'll draw more power because it's easier for all those electrical thingies to run downhill to the amp. Mark  |
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DYohn
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Post by DYohn on Oct 28, 2017 12:23:57 GMT -5
Sounds to me like a classic case of cable-lifter imbalance. If the one side's power cable is lower than all the others', it'll draw more power because it's easier for all those electrical thingies to run downhill to the amp. Mark I was going to guess misplaced Brilliant Pebbles (tm) but cable lifter imbalance is more likely. |
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Post by mshump on Oct 28, 2017 12:28:29 GMT -5
Interesting thread. Hope the mothership can figure this out for you. I will be following, please keep us updated.
Mark
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Post by leonski on Dec 4, 2017 12:46:05 GMT -5
Resolution / Fix?
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Post by sahmen on Dec 4, 2017 20:45:32 GMT -5
The unit actually arrived today, after a more than one month "tour of duty" ...errr, "service repairs," in Franklin, and guess what: they found nothing wrong with it, so you could say it returned in the shape it was when it originally left, i.e. with a clean bill of health... Ironically, I was sort of expecting th, because I had "stumbled upon" what might have been the original cause of my problem, one day, when I wandered into the test tones/Levels menu in my XMC-1. The test-tones work fine in one Speaker preset, but not in the other one... I still haven't found the cause of that issue, and Emo Tech Support couldn't figure out what was causing it... but I digress. While in the test-tones/levels menu, I noticed, to my utter surprise, that the level of my Front Left speaker channel was raised by 4.0db, whereas it was set at around 0 or even -1 for my Front right speaker channel. It was then that I started beating my head against the wall, in recognition of how dumb the whole idea of sending the XPA-1 back to Emo had been... So it seems I inadvertently "programmed" my own channel-imbalance into the 2-channel rig via the XMC-1, and started looking for the cause everywhere else... I even reported that discovery back to Emo when I called to inquire about the XMC-1 Test-tones problem... This one has been a real "face palm" kind of discovery for me, and because of that I wish you hadn't asked... But fair is fair... My XPA-1 Gen 2 does not deserve to be accused of "crimes" it has not committed  The weird thing is, I cannot for the life of me remember when I set up that imbalance in the XMC-1... And the only drugs I take are what my doctors have prescribed... Oh well...    |
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Post by AudioHTIT on Dec 4, 2017 22:43:18 GMT -5
So that says the SA-250 should have been unbalanced too? Glad you found the problem though.
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Post by sahmen on Dec 5, 2017 0:33:17 GMT -5
So that says the SA-250 should have been unbalanced too? Glad you found the problem though. Not exactly. It is just that, for some reason, the SA-250, was better at "concealing" the initial imbalance than the XPA-1s were, but the original imbalance was still there, because once I bumped up the level of the right speaker channel in "speaker preset 1" of the XMC-1, the SA-250 responded by amping up further the sound from the right in a way that noticeably enhanced the overall balance for the better. Notice that the differences we're dealing with here are a matter of degree, because the right channel XPA-1 was also emitting sound, except that it felt more recessed and overwhelmed by the sound from the left-channel XPA-1, or so it seemed. On that front, one feature of the XPA-1 that was probably working to its "disadvantage" in this particular case (psychologically speaking) were the indicator lights that were constantly showing a weak signal-strength on the right channel XPA-1. The more I noticed the relatively languid energy of those right channel indicator lights, the more they accentuated my feeling of the "imbalance" I mentioned, and the more they strengthened my suspicion that there must be something wrong with that particular XPA-1 in question. I was slowly becoming obsessed with those lights, and that was distracting from my enjoyment of the music. The SA-250 has no such indicator lights showing the relative signal strengths of L/R channels, so I suspect that absence de-emphasized or diminished the psychological impact of the imbalance. By the way, I do have the Kill-O-Watt now, and can take the measurements you mentioned, if you show me how to. SA-250 is still in play. The XPA-1s will be installed this coming weekend, when I have some spare time |
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Post by AudioHTIT on Dec 5, 2017 6:11:39 GMT -5
... I was slowly becoming obsessed with those lights, and that was distracting from my enjoyment of the music. The SA-250 has no such indicator lights showing the relative signal strengths of L/R channels, so I suspect that absence de-emphasized or diminished the psychological impact of the imbalance. By the way, I do have the Kill-O-Watt now, and can take the measurements you mentioned, if you show me how to. SA-250 is still in play. The XPA-1s will be installed this coming weekend, when I have some spare time Years ago some designers got rid of power indicator lights because of the psychological impact they had on the listener, so what you’re experiencing isn’t uncommon. Here’s the power measurement thread, in the first post a couple paragraphs down are the instructions for using the K-O-W. Then add your measurements and I’ll integrate them into the list, and discuss any issues. Thanks for taking the time to do this. emotivalounge.proboards.com/post/911602/thread |
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Post by leonski on Dec 5, 2017 14:02:30 GMT -5
The Old 'Operator Error' Trick, eh?
Glad you finallly figured it out and will NEVER be fooled again AND have another trouble shooting arrow in your quiver.
With the fix in place? Try the SA-250 again.
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