the bigger issue for me is if the power is dirty. Played a dive bar a few weeks back and I've never had hum that bad with my jazz bass. Luckily the guitarist had a hum-debugger pedal he let me use since the hum on his guitar wasn't as bad as mine. Normally it's not a big issue, if at all, but it was so bad that even when we were all playing it was very present in the mix.
