The Krohn-Hite Model 7500, shown in Figure 1, is an all solid state, direct coupled amplifier, that provides 75 watts of continuous power (150 watts at DC), at 125 volts RMS, from DC to 100 kHz. Frequency response of the 7500 is fiat to within 0.1 db, and harmonic distortion at full power output is less than 0.1%, from DC to 10 kHz. A front panel control selects 20 db (10) or 40 db (100) of fixed gain, or zero to 40 db of continuously variable gain. The output of the 7500 can be offset ±200 volts, open-circuit, by means of a front pane! DC offset control. The 7500 provides selectable input coupling, either direct (DC) or capacitive (AC). The amplifier’s output is protected from short-circuit or other abnormal load conditions by a unique output protection circuit, that uses a modified form of foldback current limiting. The output stage is convection cooled by a special heat sink configuration. An optional rack-mounting kit (part no. RK-519) is available for installing the unit in a standard 19” rack spacing.