Guitar Pedal power supply shorts to ground

I use a power supply instead of 9V batteries for my pedals and to power my instrument. Apparently some genius back in the day made it so that pedals require that the power supply plugs, which are the barrel type, are center negative - with the outer ring as positive!?!

So, basically, the chassis and cases of the jacks carry voltage. This is fine, as long as the system is isolated. For some reason, it doesn't short when I connect it to an amplifier.

I also use the pedal power supply to power my IEM amplifier. My problem is that when I plug an XLR line in from the soundboard to this unit, it shorts the power supply.
I thought of lifting the ground from the XLR monitor supply, but this would mean building yet another box.

Any ideas?
 
I tried reversing the wires on the power input jack of my instrument power supply, and will use a center positive adapter cord which came with the PS. That way, no voltage is directly connected to the chassis. It seems to work here at home, lets see if it works with a soundboard connected.
I just think it's LUDICROUS for someone to have thought sleeve = positive was a good idea - and that most pedal companies followed along with it!