From: info@turneraudio.com.au   
      
   There was no need to pay any special attention to 50Hz mains hum.   
      
   Patrick Turner.   
      
   Don't recall anyone here saying there is a problem with power frequency   
   hum in a guitar amp. Except perhaps by bad grounding.   
      
   That is unless someone is using an SET!! Perhaps   
      
   Cheers to all, John L Stewart   
      
   Hmm, I made a 55Watt SET amp in 2009 which has 2 x parallel 845 tubes which   
   operate from B+ and B- rails, +/- 600Vdc. If ever there was a likelihood of   
   hum, it was in these amps because the B- rail must be especially hum free.   
   The schematic is at my website.   
   When completed, the noise total at speaker output with inputs grounded was   
   0.25mV, without hum being dominant, and without much GNFB. I did use CLC   
   filtered 10Vdc for the 845 cathodes.   
      
   SE amps can be very easily be made hum free but you got to get right away from   
   the accountant driven features designed into nearly every crummy amp made   
   since 1920.   
      
   Patrick Turner.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)