Blow dryer causes audible buzz from power amps in two audio systems...

Tell her to stop calling her 240v
toy a blow dryer.

Millercarbon, and several others, please don’t spread misinformation about how residential electrical systems are wired and how they work. Get a real licensed electrician who is qualified if you don’t understand this stuff. If you still want to do your own work, at least get educated on the subject, and make sure you have your electrical safety authority inspect and approve all work you do.

Sorry if this sounds harsh, but if you don’t understand the difference between neutral and ground, and the difference between grounding and bonding, and where to ground and where to bond, you are putting yourself and your families in danger if you undertake your own electrical work. For the record, residential electrical feed is single split phase. 

i used to have an audible hum in my system. I thought at first it was a ground loop and chased it for the better part of a year. I replaced every power supply with low noise, all power cables were upgraded, isolation was added, all fuses switched to synergistic, ps audio noise harvesters, I tried hum -x  and on and on. I even took one of my amps in.
Turns out it was the bug zapper in my detached garage. DC on the line i guess. 
On the bright side, all those upgrades and I have an incredibly accurate and quiet system now. 

For the record, residential electrical feed is single split phase.

Technically true, but I never suggested the OP should do this him/her self.

Best,
E

Sounds like you have it down to two choices- get rid of the hair dryer
or the wife. Your choice.