Hammond 850NA Sealed 150/600:10K/40K Interstage Audio Transformer

The 850NA is a sealed 850A Series broadcast-quality audio transformer listed for output to line, matching or interstage work. It steps a nominal 150/600 ohm primary up to a 10K/40K ohm secondary, useful for feeding a line or low-impedance source into a high-impedance stage. Nominal winding resistance is 65 ohms primary and 4980 ohms secondary (+/- 20%).

Per the part drawing, frequency response is ± 0.5 dB max. from 20 Hz to 20 kHz (the series sheet notes units over 5K ohms may be down 1 dB at 20 kHz), typical output power is +15 dBm (31.623 mW) and distortion is below 1% at 20 Hz under full power. Typical DCR is 16.9 ohms (BLK–WHT = BRN–ORG) and 1258 ohms (BLU–RED = GRY–YEL), dielectric strength is 250 V RMS, and primary inductance is 226 mH (5.58K ohms) with halves joined or 776 mH (19.82K ohms) in series, with leakage inductance of 270 uH and 1.08 mH.

The drawing describes a sealed case with an epoxy-potted transformer (the series sheet refers to a wax potted core). An electrostatic shield between primary and secondary is connected to the green lead. Humbucking construction and balanced split windings on both sides add circuit versatility, and the primary may be used as the secondary and vice versa for impedance matching.

The case is deep-drawn steel with a tin plated finish, sealed, and fitted with two 6-32 mounting studs; mounting hardware is included. Leads are a minimum of 4" long. The listed overall dimensions are A 1.20 in (30 mm), B 1.70 in (43 mm), C 1.65 in (42 mm) and D 1.32 in (34 mm). Drawing tolerances are ±0.063" on A, B and D, with C 1.65" max. The 850NA is RoHS and REACH compliant, with a listed shipping weight of 0.43 lbs (0.20 kg) and UNSPSC 39121301.