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Post by The History Kid on Nov 9, 2019 1:39:00 GMT -5
After going back and forth with a few things, I finally settled back to a pair of XPA-2's and a UPA-5 in my system. The XPA-2's are bridged and run to a Parasound 200 Pre, with HT Bypass over to my Denon 4200. The UPA-5 runs right into the Denon. The UPA-5 is totally silent. If there is no signal, I don't hear anything from my speakers - as it should be. However, when no signal is running to the XPA-2's, I get a lot of dead air noise, as if the gain is elevated. My initial presumption was ground loop, but moving the power source to different outlets and different cables does not change the sound. Here's a few other things I tried with no change: - Unplugging the source from the amplifier - this isolated the issue to the amp power cable, the speaker cable, the speaker, and the amplifier itself.
- Different speaker wire, both SVS speaker cable and Emotiva - ruling out speaker wire.
- Tried a different speaker. The noise is the same in both, ruling out the speaker.
- Different power outlet.
- Different power cable.
- Different power filter.
- Turning the meter lights on and off.
- Turning the indicators on and off.
- Switching to un-bridged mode does not change the level.
It's worth noting: BOTH (2) XPA-2's do this. It isn't limited to just one or the other. Any other thoughts? I have problems thinking it's a defect, since it's two of them. |
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Post by Gary Cook on Nov 9, 2019 3:33:03 GMT -5
Non English first language?
I suspect what you mean is;
Denon 4200 ------> Parasound 200 --------> XPA-2 -------> FR and FL speakers
and
Denon 4200 -------> UPA-5 -------> Surround Speakers
If the XPA-2 is a Gen 1 then they have 32 db gain, Gen 2's have 29 db gain. With the wattage and gain any introduced noise will be amplified more in the XPA-2's than the UPA-5 with its lower wattage output, plus running them bridged doubles that amplification. It doesn't take much introduced noise to be audible with that amount of power amplifying it.
My first suggestion would be to unbridge the XPA-2's and try them one channel at time. That will determine if its one channel or both in each, plus you will get some indication of the effect of riding them.
Cheers
Gary
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Post by The History Kid on Nov 9, 2019 11:19:37 GMT -5
Non English first language? I think it's pretty clear what I meant - since you understood and that's exactly what I said. :\ There are two XPA-2's, a UPA-5, a Parasound 200 Pre, and a Denon 4200. The path for most of the signal for the XPA's goes simply from the source to the Parasound, to the XPA's, and then out to the speakers. The Parasound has HT Bypass, which when active brings the Denon into the mix, but 9 times out of 10, that's not the case. If you read further in the post, you'd see that I tried this. I unbridged the amps already and tried running to each channel, there's no change. |
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Post by repeetavx on Nov 9, 2019 11:31:20 GMT -5
My first guess would have been the bridging too. Especially because my gen.1 XPA-2s are dead silent with my 93db speakers. If your speaker are more efficient than that, then that could be the problem. If not higher speaker efficiency, then maybe power line noise or DC offset. I run both of my XPA-2s through a CMX-2. |
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Post by The History Kid on Nov 9, 2019 11:44:01 GMT -5
My first guess would have been the bridging too. Especially because my gen.1 XPA-2s are dead silent with my 93db speakers. If your speaker are more efficient than that, then that could be the problem. If not higher speaker efficiency, then maybe power line noise or DC offset. I run both of my XPA-2s through a CMX-2. These are 98 db. But I have tried with 96, 95, and 93 dB sensitive speakers with similar results. Both run through line filters, but I haven't tried them right to the wall yet. I can't imagine that the innards are that much vastly different from the CMX-2, the ones I use are APC G5's. (I have 2 in the rack). |
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Post by Gary Cook on Nov 9, 2019 15:53:36 GMT -5
Non English first language? I think it's pretty clear what I meant - since you understood and that's exactly what I said. :\ There are two XPA-2's, a UPA-5, a Parasound 200 Pre, and a Denon 4200. The path for most of the signal for the XPA's goes simply from the source to the Parasound, to the XPA's, and then out to the speakers. The Parasound has HT Bypass, which when active brings the Denon into the mix, but 9 times out of 10, that's not the case. If you read further in the post, you'd see that I tried this. I unbridged the amps already and tried running to each channel, there's no change. Moving on, as with all fault finding it’s a matter of testing (changing) one thing at a time and noting the results, then moving on to the next test. With half the amplification (ie; unbridged) there is still some noise or still the same level of noise? Across all 4 channels of output there is some noise or the same level of noise? A noise (SPL) meter is more reliable than ears (my ears anyway), if you have one what’s the noise dB? Obviously you need to allow for any ambient noise first (ie; measure the ambient with the amps powered off) to establish a base line. My view would be that it’s highly unlikely to get 2 x XPA-2’s with exactly the same technical issue in all 4 channels, could happen of course, but highly unlikely. This leaves introduced noise as the most likely guess. I’d definitely try a test first with power supplied direct from the power point, no filters or conditioners. It’s been my experience that they create more problems than they solve. A test that I have applied many times is to move the power amps to the centre of the room, run the power and speaker cables with as much distance between them as possible, straights runs, no parallel runs, not along walls. What’s the noise like with that configuration? If it’s the same then you might need to try another room, another location, in the middle of the backyard is a good one, or a friend/relative/neighbours house. It’s a process of elimination, one step at a time, so perseverance is required. Cheers Gary |
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Post by klinemj on Nov 9, 2019 19:59:30 GMT -5
A few questions:
1) Gen 1 or Gen 2 XPA-2? As Gary notes, the Gen 1's were 3 dB higher in gain.
2) Can you post a recording of the sound? If not, is it a hum, a buzz, or...what?
3) When you switched outlets...same circuit or different?
4) Got any dimmers on the circuit?
Mark
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Post by The History Kid on Nov 9, 2019 21:36:55 GMT -5
My view would be that it’s highly unlikely to get 2 x XPA-2’s with exactly the same technical issue in all 4 channels, could happen of course, but highly unlikely. This leaves introduced noise as the most likely guess. That's my presumption. Two identical XPA's having this issue seems like a improbability. 1) Gen 1 or Gen 2 XPA-2? As Gary notes, the Gen 1's were 3 dB higher in gain. We are dealing with a pair of Gen 1's. I'm not sure it'd translated well in a recording. I'd describe it as a soft hiss. Consider what noise you might get if you turned the gain on a source all the way up with nothing playing back. It isn't loud by any means, it's just very noticable, especially at lower volumes. Considering how this house is wired (icky), we're dealing with the same circuit in the room. None to report. |
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Post by klinemj on Nov 9, 2019 23:08:00 GMT -5
My view would be that it’s highly unlikely to get 2 x XPA-2’s with exactly the same technical issue in all 4 channels, could happen of course, but highly unlikely. This leaves introduced noise as the most likely guess. That's my presumption. Two identical XPA's having this issue seems like a improbability. 1) Gen 1 or Gen 2 XPA-2? As Gary notes, the Gen 1's were 3 dB higher in gain. We are dealing with a pair of Gen 1's. I'm not sure it'd translated well in a recording. I'd describe it as a soft hiss. Consider what noise you might get if you turned the gain on a source all the way up with nothing playing back. It isn't loud by any means, it's just very noticable, especially at lower volumes. Considering how this house is wired (icky), we're dealing with the same circuit in the room. None to report. Given you say you have hiss, it sounds like the amp gain is way too high for your speakers, and given you have very efficient speakers - they are magnifying the sound. A ground loop would be a hum/buzz - not a hiss. You can get some in-line resistors that put the gain in check by varying degrees of dB. I'd look into those for the XPA-2 Gen 1's. I used some for a while myself and I think I have them sitting around in my extra gear pile. I bought them at Parts Express, if I recall correctly. If I can find mine, I'd happily send them to you for cost of shipping or if you are in Cincy area - we can meet and I'll give them to you. Mark |
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Post by klinemj on Nov 10, 2019 10:19:03 GMT -5
Here are the attenuators.  Mark |
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Post by The History Kid on Nov 10, 2019 15:31:42 GMT -5
Given you say you have hiss, it sounds like the amp gain is way too high for your speakers, and given you have very efficient speakers - they are magnifying the sound. A ground loop would be a hum/buzz - not a hiss. You can get some in-line resistors that put the gain in check by varying degrees of dB. I'd look into those for the XPA-2 Gen 1's. I used some for a while myself and I think I have them sitting around in my extra gear pile. I bought them at Parts Express, if I recall correctly. If I can find mine, I'd happily send them to you for cost of shipping or if you are in Cincy area - we can meet and I'll give them to you. Mark Thanks for the offer. I do have some questions about the use of in-line resistors though: 1. Would this not mean that the amplifier may need to work harder to achieve a certain variable of loudness? For example (and the Parasound isn't using SPL for volume), the Preamp right now is about at a level of 20 to produce 85-90 dB of SPL, would a resistor in line require that to be on the increase to achieve the same effect? 2. You mention you used these for a while. That implies you stopped at some point. What changed, if you don't mind my asking? I'm not opposed to trying this idea, I just want to know what I'm getting myself into beforehand. I've been having a hard time with "surprises" lately. |
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Post by vcautokid on Nov 10, 2019 16:34:37 GMT -5
I have thrown this one in from time to time because it has bitten me and some other custom audio buddies of mine. Any Cable TV provider services?? A great source of noise to a greater or lesser degree in some systems. My system in L.A. was getting some buzz and sure enough the Cable was not properly grounded and the cable decoder too was doing its noise deal too. Isolated both of those and it didn't matter what amplification I used. Just throwing again that out there. Might help, might not. But something worth checking out.
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Post by klinemj on Nov 10, 2019 16:37:07 GMT -5
Given you say you have hiss, it sounds like the amp gain is way too high for your speakers, and given you have very efficient speakers - they are magnifying the sound. A ground loop would be a hum/buzz - not a hiss. You can get some in-line resistors that put the gain in check by varying degrees of dB. I'd look into those for the XPA-2 Gen 1's. I used some for a while myself and I think I have them sitting around in my extra gear pile. I bought them at Parts Express, if I recall correctly. If I can find mine, I'd happily send them to you for cost of shipping or if you are in Cincy area - we can meet and I'll give them to you. Mark Thanks for the offer. I do have some questions about the use of in-line resistors though: 1. Would this not mean that the amplifier may need to work harder to achieve a certain variable of loudness? For example (and the Parasound isn't using SPL for volume), the Preamp right now is about at a level of 20 to produce 85-90 dB of SPL, would a resistor in line require that to be on the increase to achieve the same effect? 2. You mention you used these for a while. That implies you stopped at some point. What changed, if you don't mind my asking? I'm not opposed to trying this idea, I just want to know what I'm getting myself into beforehand. I've been having a hard time with "surprises" lately. You would be "throttling" the amp, so - yes...it would have to work harder. But, right now, with 32 DB of gain with 96 dB efficient speakers...your XPA-2 is on idle. It's go plenty of power to spare. I can't recall why or when I stopped. I don't really think I needed them in the first place. Mark |
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Post by The History Kid on Nov 10, 2019 17:21:52 GMT -5
I have thrown this one in from time to time because it has bitten me and some other custom audio buddies of mine. Any Cable TV provider services?? A great source of noise to a greater or lesser degree in some systems. My system in L.A. was getting some buzz and sure enough the Cable was not properly grounded and the cable decoder too was doing its noise deal too. Isolated both of those and it didn't matter what amplification I used. Just throwing again that out there. Might help, might not. But something worth checking out. I have heard that before as well, but we cut the cable before we even moved to where we are now - so no cable signal is in line outside of the internet which is all Wi-Fi excluding the POE. You would be "throttling" the amp, so - yes...it would have to work harder. But, right now, with 32 DB of gain with 96 dB efficient speakers...your XPA-2 is on idle. It's go plenty of power to spare. I can't recall why or when I stopped. I don't really think I needed them in the first place. Mark Sounds good enough. I know that it's rare for me to push the XPA's all that much judging by the meters hardly moving on normal use. I'll be in touch this evening. Thank you again for the offer, I'm willing to try just about anything at this point. |
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Post by Gary Cook on Nov 11, 2019 0:54:34 GMT -5
I can't recall why or when I stopped. I don't really think I needed them in the first place. Mark They were trendy a few years back with Gen 1's and their gain of 32. Good for AVR's at the time but not so much for decent pre maps like the USP-1 for example, where they got very loud very quickly at even modest settings of the volume knob. Particularly when using the remote where the volume would go from just audible to blow your ears in one click of the remote. Attenuators fixed that problem. Cheers Gary |
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Post by klinemj on Nov 11, 2019 8:37:14 GMT -5
I can't recall why or when I stopped. I don't really think I needed them in the first place. Mark They were trendy a few years back with Gen 1's and their gain of 32. Good for AVR's at the time but not so much for decent pre maps like the USP-1 for example, where they got very loud very quickly at even modest settings of the volume knob. Particularly when using the remote where the volume would go from just audible to blow your ears in one click of the remote. Attenuators fixed that problem. Cheers Gary The USP-1's volume control may be why I had them. That was a very touchy volume control, and I was using the XPA-2 with it. Mark |
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