http://margo.student.utwente.nl/el/
tubes

/guitaramp     Guitar amplifier.
/other         Other stuff.
/poweramp      Power amplifier.
      /otl     OTL ?.
      /pp(p)   Bob. D.'s Push-Pull Class A 2A3 Stereo Amp.
      /se      Some audio amps.
/preamp        Pre-amplifier.

tubecalc  .zip     Small program to help calculate the basic parameters of a
                   push-pull transformer coupled output stage.  It works for
                   all modes of operation and on triodes or pentode.