The 1642SE is a single-ended classic tube output ultra-linear transformer designed for 75-watt audio applications with a frequency response of 20 Hz to 20 kHz. It features a primary winding with 5000 O impedance and multiple secondary taps providing 4 O, 8 O, and 16 O output impedance options to accommodate various speaker configurations. The transformer includes comprehensive electrical specifications including a maximum excitation current of 12 mA at 240V 60Hz, secondary no-load voltages of 6.720V (4 O), 9.600V (8 O), and 13.44V (16 O), and DC resistance values of 240.0 O on the primary and 0.950 O on the secondary. With a maximum DC bias of 300 mA and frequency response flatness of ±1 dB at 1 kHz, this transformer is ideal for vintage and modern tube amplifier designs requiring reliable impedance matching and audio fidelity.