[BC] Humming Preamps

[RadioPower Webmaster]

I'm still having issues with humming in all our mic, stereo, and  
phono preamps. It's a buzzing sound that seems faster higher  
frequency than 60 cycle hum. More like RF static. It happens in all 4  
of our studio booths on two floors. It's so bad we can't use our  
turntables. I got an electrician to come out and he ran new ground  
wires for the building service and switch panel and replaced old  
vibrating breakers. It still hums. He suggests running 20 amp lines  
with isolated ground to plug strips for each booth. Before I lay down  
another $800 does this sound like it might fix our problem? Also do  
the high end $450 Furman or Monster power conditioners work any  
better than the $150 Furman PL-8 rack mount conditioners we have? I'm  
starting to fear thousands spent in a wild goose chase. By the way a  
Verizon tech had to install inline RF filters to cut the humming and  
noise from our phone hybrids. I've never met a building this noisy.

Thanks in advance.

Shelby