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Post by speedysteve on Jun 22, 2016 16:49:10 GMT
Got a new Crown XLS 1500 for my mid bass channel.
Problem is pronounced bass hum at anything more than 70% volume.
It replaced a Topping TP-60 that hummed a little bit on max vol & I've briefly tried a Cerwin Vega CV1800 and Behringer Inuke 1000. Neither of which hum at all even on 100% vol.
I returned the XLS 1500 & got a XLS 1002 new generation.
Love the features and the sound, but it also hums.
Can both Crown amps really be faulty?
If the Behringer and the CV also did it I'd be fault finding elsewhere..
I like to run it flat out as it sounds better with the gain structure like that. Minus the hum of course!
The mid bass are exponential horns of about 110dB/W efficiency using JBL 2220H 15" drivers. So yes they amplify the hum.
Have any of you amp guys had similar problems with Crown?
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Post by jandl100 on Jun 22, 2016 17:08:05 GMT
I had an XLS 1500 for a while.
I vaguely recall that it did hum a bit with gain at max, but as there was more than enough gain I just backed it off a bit and it was fine.
I can imagine that with something like an extra 25dB in efficiency with your horny things compared to my speakers it may well be quite a problem.
Quite a decent amp - didn't feel like it actually had the rated power on tap, though. Sounded a bit lacking in oomph, tbh. Not the last word in rez, either. But pretty decent.
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Post by John on Jun 22, 2016 17:17:25 GMT
Sounds like the amp Steve
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Post by speedysteve on Jun 22, 2016 17:47:29 GMT
Yes John, but two, even of different generations....
Or did you mean hum is designed in. That'd be disappointing indeed.
Crown have such a good rep.
The Cerwin is 18kgs of torroid and silicon and heat sinks. No hum.
Considering sending the XLS1002 back and getting another CV.
Will swap em over first and see how the CV does on Midbass again.
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Post by John on Jun 22, 2016 18:19:21 GMT
Remember they for PA systems not hifi
I know on thh Hawthorne site people like them but they cross over pretty low with that arrangement
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Post by speedysteve on Jun 22, 2016 18:24:06 GMT
Yes PA of course, but the budget Behringer manages it, as does the not so budget Cerwin Vega. The new Crowns are black and look ok. The Cerwin is black and looks even better  |
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Post by John on Jun 22, 2016 18:29:45 GMT
I sprayed the Inuke black which of course Mike would improve
The Inuke does a great job low down
I must admit I was really liking the variable fan idea and would of been tempted in the future with this route
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Post by speedysteve on Jun 22, 2016 18:53:56 GMT
Yes the fan system in the Crown's really works well. I can just see through the grille at the front to the white wall at the back. When a more demanding music passage comes the fan spins up quite slowly in my use and you can't see the wall, once cool it slows again and the wall is visible - first level of signal leds lighting occasionally. It's still silent and you can just feel a slight air movement. I'm sure if driving it hard it would be on a lot more. Halving the voltage on the Cerwin (running both fans off one fan psu), AVforum top tip solved the noise and still gives useful air flow for Hifi use. The Cerwin has two 24v fans they said |
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Post by MartinT on Jun 22, 2016 21:29:34 GMT
Is the Crown an earthed amp (i.e. uses a three-pin power input)? I take it the hum is variable and comes through the speakers?
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Post by speedysteve on Jun 22, 2016 23:34:52 GMT
Is the Crown an earthed amp (i.e. uses a three-pin power input)? I take it the hum is variable and comes through the speakers? I'm using the cable that came with it. Not sure it's an earthed cable, will get multimeter on it tomorrow. My sockets and distribution blocks are defo earthed  Yes, increases with volume. Audible at about 70% vol and up. Very audible at full vol. It's not input vol dependant, all amp. I've checked usual cables and don't have mains running near phono / speaker cables. It's not that though as the other two PA amps are clean... |
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roy
Rank: Trio
Posts: 116 
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Post by roy on Jun 23, 2016 1:02:32 GMT
Ran two in bridged mode (one of them was Jerry's) and never had a problem with hum.
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Deleted
Deleted Member
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Post by Deleted on Jun 23, 2016 4:36:22 GMT
Firstly in bridge the Hum would cancel if it was a problem with the PSU Ripple in the power section so no HUM.
Secondly are the ex USA version ?
If so the mains is 60Hz no 50Hz so the 100Hz ripple we have instead of the 120Hz the US will have mean, to get the same amount of PSU ripple rejection you would need large caps.
And if there is input filter to reject 120/60Hz then it is not working.
Now more likely you have a input hum loop or earth loop, or the huge transforms because the are now on 50Hz and not working to spec could be saturating and inducing hum into you system by proximity coupling. So move them away from things and try again.
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Post by speedysteve on Jun 23, 2016 9:01:16 GMT
Thanks for the input. Hmm, def 240v model. Says so on box and on chassis. I'd get all that and be trying lots of things if I had a root problem. Don't think I have as the Behringer and Cerwin Vega are totally silent.
Bridge nmode would give me power I don't need and mean I'd need another amp. I suppose I could try the Crown bridged on ch1 & the Behringer bridged on ch2 but not really a good solution.
Puzzling. I'll try a few things today. Try the Cerwin on the mid bass again and if it performs as well as the Crown, the Crown will be rejected as not fit for purpose and another Cerwin will be on the way |
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Post by speedysteve on Jun 23, 2016 18:08:04 GMT
I have tried a few things.
Changed the mains cable and tried earthing the case. An improvement came moving the Crown away from the other equipment. It's almost ok now!
I'm not sure why the Crown would be more sensitive to this than the other amps. For the intended use you'd think they'd have to be very well shielded.
Ok it is more powerful that the Behringer but less powerful than the Cerwin Vega!
Perhaps in a rack full of new generation PA chip amps it would be fine?
So it could be my setup not suiting it / it's a bit of a sensitive flower!
More fiddling to come.
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Post by speedysteve on Jun 27, 2016 19:35:45 GMT
The plot thickens. Having relocated the amp, I changed the mains cable to my bespoke one made from uber German shielded cable. After that it's totally silent, no hum at all. So it seems my set up / other equip upsets the Crowns, where the other amps don't mind. Now I can focus on the sound quality I'm getting. I'll do another measurement session for the new amps, see if the room corrections still apply with beefier amps. Happy not to have hum for the moment |
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Post by MartinT on Jun 27, 2016 20:09:42 GMT
It's good that you can compare them properly, now.
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Post by John on Jun 28, 2016 4:08:37 GMT
Good news
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