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.