Seriously, modern amps tend to be more sensitive to power issues, particular the new light weight amps. You need to check the outlet, and it doesn't hurt to know that you are getting full and clean power as well, which many outlet testers will not accurately convey, hence the use of power conditioners. I confess to only using a Radio Shack outlet tester myself and I did have trouble with insufficient power at 2 outdoor gigs where the band was strung off of one set of outlets. The BX500 may go into protect mode when facing insufficient power.