For use in a valve compressor or amplifier using either an AC coupled SE or PP output stage. Can be used with a secondary load resistor; for example 200 Ohms will provide a constant reflected anode-to-anode load of 16000 Ohms when the amplifier is feeding a high impedance load. This also lowers the effective output impedance of the amplifier and may be adjusted to define the amplifier gain. When used with a PP output stage the quiescent DC anode currents must be balanced to within 0.5mA. Combination core using high grade Grain Oriented Silicon Steel (M6) and Mumetal. This provides high level capability, wide bandwidth and transient response maintained over the full dynamic range. This core also permits the use of a relatively high ratio which ensures minimal loading of the anode and a low output impedance for driving lines or complex loads. Suitable for Drip UA175B.