Sorry for the late response - catching up after return from vacation.
I've successfully simulated numerous p-p valve (tube) amp circuits using the simple model posted by the OP, albeit with higher values of inductance as pointed out by John Woodgate. Staying within linear range for input signals (ie little ouput distortion) gives good agreement between simulated and actual performance as measured on the bench.
Eg. The SOVTEK Mig 50 (50w Marshall copy) usies EL34s (6CA7 equivalent) and the measured values of the primary inductors are 6H with a series resitance of 64ohms. Guitar amps only need to have a limited? bandwidth of approx 100Hz - 5kHz.
Hi-Fi quality transformers will typically have higher values of inductance for a similar power output - but they'll weigh considerably more. Believe me, I know from bitter experience that the transformers in 50w - 100w guitar amps are more than heavy enough!
Martin
