![]() The voltage taps I ended up with would allow for some adjustment. A voltage doubler circuit would be used, like everyone else uses. I would wind my tranny with 3000 volts in mind but with a few taps. So I happily hung my hat on that idea and reinforced it with tales that 813 tubes were "rugged". ![]() I seem to recall from too many years ago that a linear amplifier derived huge benefit from as high a B+ as possible and linearity was much dependent on a low impedance power supply. I must disclose at this stage that several people said that I should use two 813 tubes rather than one. My junk heap had produced a 60V 1KVA 'tranny' which I could rewind for a perceived 2800 V supply. ![]() In consideration of modest power needs, the neighbours, the legal power limits and even the availability of tubes, a single tube version became the initial aim. ![]() The principle of this bifilar solution was also shown in SSB for Radio Amateurs. The claimed performance and especially the 813 input circuit arrangement used by ZL1AXB seemed most attractive. That success encouraged me to try and make an 813 linear. My first homebrew linear used used four PL519 tubes in parallel and works very well.
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