[Valvepower]

Hi Tim,

I tried using the grid and ia curves etc., to arrive at some values for the EF184, however I gave up and used the curves as a very rough guide to arrive at total ball park figures for the starting values and went in an entirely non-technical method to arrive at the required values for the cathode, anode resistors the screen grid voltage.

I built a pile of wires hook-up with a range of anode resistors and used a variable resistor in the cathode to set the bias and varied the screen grid voltage using a pot. All very non-scientific, but I arrived at workable values.

I fed the “pile of wires hook-up” with a signal generator and monitored the output using a Scope and VVM. I had the luxury of a THD analyser so I could measure the THD.

I looked for symmetrical clipping with the maximum output voltage with the minimum of THD.

I swapped out valves to make sure it’s works with a selection of valves from the toy box.

I’ve noted the EF184 can be microphonic causing some problems, but with using Brimar valves (they appear less microphonic than the Mullards) and using some salvaged shock mount bases the microphonics can be tamed.

Regards
Terry