sorenj07 wrote:mesherm wrote:Actually you can get about 18 watts in triode if you put in a UF4007 diode in series with the 100 ohm resistor. The cathode of the diode has to be pointing toward the screen. This keeps AC from flowing in the screen grid/plate circuit.
http://www.audioasylum.com/forums/DIYHiFi/messages/6928.html
You realize that guy quotes Dennis Fraker right? Just thought you should know. I've seen this called a myth, can't find the link right now, and it seemed credible. The main argument (IIRC) was that AC doesn't flow to the screens in the first place.
I have never heard of Fraker. However, Grimwood knows his onions about tube amps.
http://www.webace.com.au/~electron/tubes/oes.html
"Another and previously unpublished option to creating an operating environment where the Screen Grids will be at a DC potential sufficiently high enough to attract and accelerate electrons towards the Plates but, to maximise power output, not to collect and divert them to earth through the B+ supply, is the humble silicon diode semi-conductor rectifier.
By inserting a standard half-wave silicon rectifier diode in series with the Grid Stopper resistor, an electronic control circuit is created whereby the Screen Grid will be able to be energised at DC potential attracting and accelerating electrons towards the Plate - still electrostatically controlling current flow in the normal way - but blocking the flow of AC current from the Screen Grid back to the DC source - ie "one way traffic"
This works because the current flow in the tube is always from the Cathode to the Anode (Plate). The diode, being a semiconductor, blocks current flow in the reverse direction, thus enabling DC current to feed it in the conventional manner but blocks AC current from passing back through it to a load."