The Copland CTA408 has two taps on each of its output transformers, one 8H and the other 4fl, yet Copland specifies the power output of the CTA408 into 8H and 3H loads. Irrespective of the tap you use, output power is rated at 75-watts per channel.
Newport Test Labs first measured output power using the 8H taps and 8H test loads. At 1kHz, the CTA408 exceeded its manufacturer’s specification by 23-watts when both channels were driven and by 28-watts when only a single channel was driven, returning power output results of 98-watts per channel and 103-watts per channel.
When the same tap was used to drive 4H loads at the same frequency the Copland CTA408 delivered 135-watts when only a single channel was driven and 110-watts per channel when both channels were driven.
Power output dropped off at the frequency extremes, as you can see from the tabulated figures. At 20kHz the Copland CTA408 delivered 50-watts per channel both channels driven into 8H,
