In Reply to: Andy Evans is your man (nt) posted by danlaudionut on July 26, 2014 at 23:50:31:
I've been using a 4P1L into 4P1L PSE amp for 2 years and no desire to build anything else. I'm that satisfied. Bought 150 tubes so I'm future proof. It all has to be in filament bias - you're throwing away quality if you don't use filament bias right through. Lundahl iron - LL1660/25mA and LL1620/80mA. No coupling caps or cathode bias caps. Simple 2 stage design, but complex power supplies!
I've built 2a3, 6B4G and 300B amps and this is better than all of them, mainly because I only need 2 DHT stages since mu of 4P1L is over 10. And with filament bias you lose the cathode bypass caps which I hate. Apart from the gain favouring the 4P1L they're all good tubes, but you can't use the 2a3/6B4G/300B in filament bias. Or rather you'd be nuts to try.
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