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K2 odd signal light behaviour


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#1 Wrighty

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Posted 08 August 2011 - 10:09 AM

I was doing a gig on Saturday night with a couple of K2s - one driving a pair of FOH speakers and the other driving a pair of wedges. There was a DJ there with his own rig too, playing his stuff between the band's sets. After the band's first set, I went over to the amp racks to make some adjustments to the crossover and noticed that the signal lights on the K2 driving the FOH speakers were lighting in time with the DJ's music. I had no signal going into the K2 at the time. The amp was in standby (because it had no signal). When I disconnected the speakers, the signal lights went out. Upon reconnecting each in turn, each signal light started flashing in time with the DJ's music again. It was as though the speakers were acting as microphones and the signal LED circuitry was somehow picking the tiny signal up. The second K2 driving the wedges was behaving normally (ie. signal lights off). The amp worked fine for the whole gig, in spite of this!

Any idea what could cause that behaviour, before I dig out the service manual and start investigating? I've yet to try reproducing the fault on the bench.

Cheers,

Richard Wright

#2 Kevin Heber

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Posted 10 August 2011 - 08:12 AM

Yes, this was a well-known feature of the K2 wink.gif

#3 Wrighty

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Posted 10 August 2011 - 02:26 PM

QUOTE(Kevin Heber @ Aug 10 2011, 02:12 PM) View Post
Yes, this was a well-known feature of the K2 wink.gif


Oh, really? Never noticed it before, but then again, there isn't usually another rig running in the same venue! How come the other one wasn't doing it then? And what causes this odd behaviour? Something to do with certain parts of the amp being powered down when the sleep circuit is active?

#4 Kevin Heber

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Posted 11 August 2011 - 01:34 PM

Probably not efficient enough speakers on the other amp to trigger it, just a guess.   It has to do with the design of the signal indicator circuit.

#5 kevvywevvywoo

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Posted 12 August 2011 - 02:17 PM

Sounds like your speakers were acting like microphones and generating enough voltage (courtesy of the DJ's system)  to light the signal lights. This happens on a few amps (not always Crown) where the signal LED circuitry is driven off the scaled output voltage; dont worry about it.




#6 Wrighty

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Posted 13 August 2011 - 05:12 AM

QUOTE(kevvywevvywoo @ Aug 12 2011, 08:17 PM) View Post
Sounds like your speakers were acting like microphones and generating enough voltage (courtesy of the DJ's system)  to light the signal lights. This happens on a few amps (not always Crown) where the signal LED circuitry is driven off the scaled output voltage; dont worry about it.


That was my first thought but having never seen it before, I was slightly surprised when I did!

Thank you both for your replies smile.gif