Hi Jim, You may view the Eimac numbers for a 4-1000A in GG on my website: http://wc6w.50webs.com/wc6wamps/index.html?fr53.html Two tubes will be very close to 50 ohms input impedance. They will also lower the output impedance easing the Pi-Net requirements. A lot depends on how much Plate V you're running. 73 & Good morning, Marv WC6W -- "Jim Isbell, W5JAI" wrote: I have not heard anything from this list in months so maybe I am not still subscribed. Please respond directly to me just in case. I have two Linears that use 4-1000A tubes. One is a single 4-1000A and the other has two tubes in parallel. Is there an advantage of one over the other if both are run at the limit for the Ham Bands? Even the single tube will not be over stressed at that level with 3500Volts on the plate. Will the drive requirement be lower using two tubes? I don't understand why the two different designs were built as they were both built by the same Ham. One must have had an advantage. -- Jim Isbell "If you are not living on the edge, well then, you are just taking up too much space." _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ________________________________________________________________________ Interested in getting caught up on today's news? Click here to checkout USA TODAY Headlines. http://track.juno.com/s/lc?s=198954&u=http://www.usatoday.com/news/front.htm?csp=24