Vegard Winge kindly sent me some great DHTs for tracing including the 307a directly heated pentode. The sample traced is not an original Western Electric but a lovely Raytheon RK 75 307a NOS. There is limited information of this valve in triode mode and the folks at DIYaudio are looking at potentially using it for a DHT headphone amp.
This valve has a filament of 5.5V and 1A and an anode dissipation of 21W in class A (including screen dissipation) when triode-connected.
Let’s see how this valve performs in triode-mode:
How well can we match a triode model for this valve?
