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

Hi,
DC present in line is common and is not minimized or eliminated if you have a dedicated line for Audio and does not go away if you use different wall sockets. A nearby station may also be affected occasionally and distribute DC to your home line easily. To make things more complicated not only hair dryers but dimmers, refrigerators, led power supplies, micro wave ovens load DC to a line. Few audio equipment use DC filtering, the rest are more sensitive and their transformers will produce noise and heat most of the time. I have found a way to eliminate the problem through a dedicated DC filter (made of 12x 4700mf/25v caps, one for Power amp and one for sources and preamp). Sonically they are not subtracting .
George

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