Available Output Power
The power available from an audio amplifier, for a given THD figure, is an important aspect of the design. Although there are a number of factors that will influence this, such as the maximum permitted anode voltage or the maximum allowable cathode current, the first of these that must be considered is the permissible thermal dissipation of the anode of the valve. These limiting values are quoted in the manufacturers’ handbooks, and from these it is possible to draw a graph of the kind shown in Figure 11.18, where the maximum permitted combinations of anode current and anode voltage result in the curved (dashed) line indicating the dissipation limits for the valve, and the load line for its particular operating conditions can then be superimposed on this graph to confirm that the proposed working conditions will be within these thermal limits.
