Pleiades EF183 Audio Power Amplifier in Class A1 Operation

 At your risk.

While contemplating building a single ended EL84 power amplifier driven by a 1;12 input transformer instead of a driver electron tube...

It was decided to try the EF183 as a triode connected power amplifier which has a similar pinout and much less power consumption.

It sounded expressive, loud and smooth.

Operating conditions:

Vb=120V

V(Rk)=2.4V (V across 120ohm cathode resistor) hence

Ik=20mA

Ck=100uF

input transformer 1:12

output transformer 5Kohm:4ohm 3Watt, (possibly from Collins receiver)

Rg=470Kohm

input transformer is coupled to control grid by use of a coupling capacitor  

Signal Path:

Big in Japan-Alphaville, on CD - SONY CD Walkman line out - Pleiades EF183 - Celestion Ditton 150 (8ohm speaker typically 30ohm at mid band).

The PSU used is a top quality component, military power transformer, 5U4 rectifier electron tube, choke input filter, paper in oil 10uF capacitor, 10Kohm 10W dropping resistor, 50uF electrolytic capacitor. All this is overrated as this PSU was intended for higher power.