Best thing to do is email George Wright. He will get back to you. Before you do, there's a couple of things to try. Replace the 6SN7's with new ones. Bad driver tubes will cause hum. Check the polarity of your outlets with one of those three-light plug testers. A reversed hot/neutral could cause the hum also. Power up the amps with just the speakers connected - to eliminate the possibility of ground loop from the IC cables. Mention to George you tried these.
I also have the 3.5's - and mine are dead quiet (although my speakers are less than 90db sensitive). There are a lot of could-be's if it's the amps, and only George can help.
I also have the 3.5's - and mine are dead quiet (although my speakers are less than 90db sensitive). There are a lot of could-be's if it's the amps, and only George can help.