I've got a crown XLS 1002 class-D amplifier, the little brother of the 1502 reviewed and pictured by ASR here
It was a second-hand bargain for which I don't know the history other than it has been stored in my living room for the last couple of months (i.e. it is not cold or damp). When I tested it, it initially seemed fine but after a while noise started appearing on one chanel only - not a hum or hiss, instead it sounded very like a microphone being gently buffetted by an intermittent blustery breeze. Choice of input or no input or (IIRC) gain knob position made no difference at all.
I know very little about class-D circuits, and these days I have almost no electronic testing facilities either. So had more or less decided to take out the electronics and just use the rack case for an end-point/renderer; it wasn't a very expensive amp, so is probably only worth so much tinkering. But... I left it powered up for several hours and the issue seems to have gradually cured itself! I don't have much chance of tracing it whilst it isn't there, which leaves me in limbo as to deciding what to do with the thing. I'm aware of electrolytic capacitors having some ability to self heal (though none look outwardly dodgy) but I have no idea if there might be other possibilities.
The best idea I currently have is to point a fan-heater at it, and 'if' that causes the issue to re-emerge then try a freeze-spray on selected components. If not then I'll probably just abandon it and get a replacement; this was to be used (for the 300hz-to-1000hz drivers) in a pair of multiple entry horns, which are going to be costly and complicated enough that I could do without possible artefacts or unreliability (or potentially even damage) from one of the amps.
But before I decide, I just wondered if anyone has any more sensible or informed thoughts on the possible cause or resolution?
Thanks,
Kev
It was a second-hand bargain for which I don't know the history other than it has been stored in my living room for the last couple of months (i.e. it is not cold or damp). When I tested it, it initially seemed fine but after a while noise started appearing on one chanel only - not a hum or hiss, instead it sounded very like a microphone being gently buffetted by an intermittent blustery breeze. Choice of input or no input or (IIRC) gain knob position made no difference at all.
I know very little about class-D circuits, and these days I have almost no electronic testing facilities either. So had more or less decided to take out the electronics and just use the rack case for an end-point/renderer; it wasn't a very expensive amp, so is probably only worth so much tinkering. But... I left it powered up for several hours and the issue seems to have gradually cured itself! I don't have much chance of tracing it whilst it isn't there, which leaves me in limbo as to deciding what to do with the thing. I'm aware of electrolytic capacitors having some ability to self heal (though none look outwardly dodgy) but I have no idea if there might be other possibilities.
The best idea I currently have is to point a fan-heater at it, and 'if' that causes the issue to re-emerge then try a freeze-spray on selected components. If not then I'll probably just abandon it and get a replacement; this was to be used (for the 300hz-to-1000hz drivers) in a pair of multiple entry horns, which are going to be costly and complicated enough that I could do without possible artefacts or unreliability (or potentially even damage) from one of the amps.
But before I decide, I just wondered if anyone has any more sensible or informed thoughts on the possible cause or resolution?
Thanks,
Kev
My experience with active systems is limited but the first thing that comes to mind is the onboard dsp. Can you update the firmware? I’ve had issues in the past with a couple Minidsp plate amps that had similar issues. The problem with those amps resulted in no output whatsoever. I ended up replacing both amps with Hypex fusion amps. Fwiw, Hypex has been excellent while a bit pricey.
Best
Best
Thanks for the suggestion, that is a very good thought; I'm not sure if the firmware can be updated, so will need to check. I know that it doesn't normally cause any problems (I have a few of these XLS amps), but I don't know what previous owners may have done/tried.
I'm not currently using the DSP, but it is still inbuilt whether used or not. All I did so far is a factory reset, which I think just restores default settings and wouldn't change the firmware itself, if something undesirable or unsuccessful has been done to it previously.
Thanks again,
Kev
I'm not currently using the DSP, but it is still inbuilt whether used or not. All I did so far is a factory reset, which I think just restores default settings and wouldn't change the firmware itself, if something undesirable or unsuccessful has been done to it previously.
Thanks again,
Kev
Well sadly there isn't a way for a user to change the firmware on these XLS amps. So I can't re-flash it but at least this means a previous owner wouldn't have been able to mess it up, either.
Most odd. In the space of a few days the noise has gone from almost always happening to occasionally happening to not happening at all. Even my attempt to use heat has failed to bring it back, since a 2.4kw fan heater pointed directly at the electronics doesn't cause it either. So until/unless it returns I supect my chances of ever diagnosing it are going to be very very slim. It simply sits there being well-behaved as if nothing was ever wrong.
I'm now reluctant to splash out on a replacement given that it somehow seems to be working absolutely fine. But obviously I'm suspicious, since there 'was' an issue that was unexplained and not addressed. So I might have to just use the amp for a while on some non-critical speakers and see how it goes. I suppose it is possible the issue may not reappear, e.g. some dampness that time in my living room didn't banish but more warmth from use has.
Most odd. In the space of a few days the noise has gone from almost always happening to occasionally happening to not happening at all. Even my attempt to use heat has failed to bring it back, since a 2.4kw fan heater pointed directly at the electronics doesn't cause it either. So until/unless it returns I supect my chances of ever diagnosing it are going to be very very slim. It simply sits there being well-behaved as if nothing was ever wrong.
I'm now reluctant to splash out on a replacement given that it somehow seems to be working absolutely fine. But obviously I'm suspicious, since there 'was' an issue that was unexplained and not addressed. So I might have to just use the amp for a while on some non-critical speakers and see how it goes. I suppose it is possible the issue may not reappear, e.g. some dampness that time in my living room didn't banish but more warmth from use has.
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Not sure but it could be bad grounding somewhere.. Heating / cooling is definitely a good way to diagnose the problem.
The only "self-healing" electronic components are film capacitors, and so that's another possibility.
https://www.doeeet.com/content/eee-...f-healing-characteristics-of-film-capacitors/
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Thanks, yes I wondered if a poor/dry joint somewhere (maybe to ground) might be responsible. The capacitor might be a more worrying possibility as it could imply something happened to cause harm in the first place, though I can't see any signs of heat/sparks or even neglect or misuse.
However, I've given it many days of use by this point and it continues to run absolutely faultlessly, so unless/until the fault reappears I'll probably never know what it was. I'm not tempted to risk breaking something that isn't (apparently) broken any more, in order to find out. By this point, I'm beginning to trust it enough to carry on using it.
However, I've given it many days of use by this point and it continues to run absolutely faultlessly, so unless/until the fault reappears I'll probably never know what it was. I'm not tempted to risk breaking something that isn't (apparently) broken any more, in order to find out. By this point, I'm beginning to trust it enough to carry on using it.