Valve (Tube-Based) Amplifiers:Effect of Output Load Impedance

Effect of Output Load Impedance

This is yet another area in which there is a conflict in design requirements, between output power and output stage distortion. Figure 11.17(a), shows the output power

given for 1 and 2% THD values by a push–pull pair of U/L-connected KT88s in relation to the anode to anode load impedance chosen by the designer. These data are courtesy of the GEC2 Since the distortion can also alter in its form as a function of load impedance, Figure 11.17(b) shows the way these circuit characteristics change as the load resistance changes. The figures given for a single-ended 6AK6 output pentode are due to Langford-Smith.