Hum problem solved. Preamp drops it's ground as part of it's protective circuit when it's cut off. Company pres said to leave it on 24/7. Tubes will last about four years.I didn't call him, he called me because I had talked with his support person about this and other hums .Amp and pre are both on--dead silence. Merry Christmas guys and thanks for your help.
claud
claud