Eddy, My latest rig is a pair of 4D32 tubes, since I got 4 new ones at $20.00 each. I have run them at 1000 volts, and 1200, even tried 1500 volts, they give about 300 watts out at 1200 volts...
My normal rig is a pair of 812A's, most were $5.00 at fests, and I get 300 watts out of them at 1500 volts, no color on the plates. Some of the 813's I have I got out of homebrew amps I got at fests, $25.00 for the entire thing.(it looked really nasty) The 813's have to be king though, 2000 or 2200 volts, and 600 watts out is easy, they seem to modulate well with a choke and a big dropping resistor from a low voltage supply for the screens. I use a screen protection circuit in all the screen grid tubes, which may be why they last. I have a blower that pulls air in from a filter and blows it out around the bases of the tubes, in case I want to push things. Great working tubes, a lot of bang for the buck, and I like the lower voltage they can run at, you can do 1000 volts, 1500, or 2000 or even 2500 volts! Brett N2DTS > Brett, > > Those 813's are practically indestructable --- and I should know, too, > having used them in my amplifier for some 16 years now (only > had to replace > the tubes ONCE!...and we're talking surplus/Hamfest jugs here, too)... > > I have examples here of BOTH the graphite AND metal plates > --- NO IDEA how > the metal plate versions retained the same "813" number --- it CAN'T > possibly be the same tube! --- but it has. > > I have yet to use the metal ones, though... > > Never could understand why guys spend the big $$$ for tubes --- albeit > modern, low drive, efficient ones --- when rugged, bargain > basement bottles > like the 813 still abound... > > ~73~ Eddy VE3CUI - VE3XZ > >
