FXs kapaw

I've been using a Digitech vocal harmoniser on stage for some time now, but last week the power supply began cutting off and making noises during the gig. I decided to bight the bullet and get a new power supply. It came Wednesday, I plugged it in and it worked great, though I only used it for a few seconds. During Saturday's gig the harmoniser was making more noise than usual, then about an hour and a half into the gig, mid song....kapaw and just a load of electrical grating noise through the speakers. I tried unplugging everything till I realised it was the harmoniser! I unplugged that and carried on with the gig, luckily I've got reverb on my mixer. It's so embarrassing all that noise. Had a great gig regardless though my hand is aching after all the hand shakes. Now I have to see what the power supply seller is going to do about it, after all the paperwork confirms it was a 9 volt but the rating on the supply says 14 VAC I take it that means 14 volts AC.ive sent them an e-mail but they may BS me with "you should have checked before using it" I'll keep you informed.