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[Closed] Electronics / audio oddity

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This could well be daft but here goes.

I've got a headphone amp that works perfectly (24v dc from wall wart, not earthed) and a small mixer that also works perfectly.

For some reason I decided to connect the headphone amp to the mixer's tape out (via rca) and it works fine.

The weird thing is that the amp is now always on - irrespective of what it's on/off switch says.

If I disconnect the RCA leads from it then it turns off / on. Or connect something else to it via rca - all fine - the switch works again.

So its not a big deal, but I'm just curious whats up, and given that something's wrong - why is it all still "working" perfectly. Any ideas?

Ive got the multimeter out but not sure what to check next.


 
Posted : 30/11/2012 8:51 pm
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Quite common: http://www.diyaudio.com/forums/parts/136636-dc-voltage-rca-output.html


 
Posted : 30/11/2012 9:34 pm
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Does your mixer have XLR inputs with phantom power?


 
Posted : 30/11/2012 9:46 pm
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Thanks footflaps: I'd not even considered that! So I should see DC on the tape out's from the mixer I guess.

dave - yep: the xlrs are shared with rca's (via simple adapters) on channel 1/2 that are connected to the computers soundcard. I've no idea if they're powered (and no user manual).

#Edit : it's one of these:
[img] [/img]

#Edit 2: The meter shows 0v dc on the rca tape outs and a happily fluctuating 0.0 - 0.3v ac depending on tunes.

#Edit 3: Is there any way the amp could be switched on neutral and the mixer is providing an earth or something? I've just tried a bench psu and its doing the same so dont think its related to the wart.


 
Posted : 30/11/2012 9:56 pm
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Edit Shoulda read all the thread! 🙂


 
Posted : 30/11/2012 10:12 pm
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No worries trampus - you got me metering the shared inputs anyway - which was worth checking.


 
Posted : 30/11/2012 10:26 pm