FR-4 suggests that the maximum temperature rise in a trace should be no more than 30°C and preferably less. Using a figure of 20°C, George Patrick’s trace calculator suggests a trace width of 4.83 mm for 1 oz copper in an outer layer, 2.41 mm in 2 oz copper or 12.55 mm in 1 oz copper in an inner layer.
No information was given on the nature of the power amplifier, but it is likely to be large, and the inference is that there are only two connections carrying this high current. Careful consideration should be given to the practicality of using wide tracks of 1 oz copper, possibly covered with solder rather than solder resist. Of course, whether or not this is practical will depend on other factors.
As an alternative, one might use the power and ground connections that will probably exist on internal planes, but a more careful analysis would need to be made as to whether the voltage reduction caused by this heavy user of current will affect other elements of the circuit. Normally it is better to route heavy currents separately.
At the 10 A level, we also need to take into account current crowding at connections. If possible, the current should be spread between multiple pins, as is often done with power semiconductors.