Hammond 850JA Sealed 150/600:1200/4800 Ohm Line to Base Transformer

The 850JA is a sealed 850A Series broadcast-quality audio transformer for output to line, or line to base, applications. It pairs a nominal 150/600 ohm primary with a 1200/4800 ohm secondary; nominal winding resistance is 69 ohms primary and 570 ohms secondary (+/- 20%).

Its part drawing specifies frequency response of ± 0.5 dB max. from 20 Hz to 20 kHz, typical output power of +15 dBm (31.623 mW), and distortion below 1.5% at 20 Hz under full power. Typical drawing values include DCR of 23.0 ohms (BLK–WHT = BRN–ORG) and 173 ohms (BLU–RED = GRY–YEL), 250 V RMS dielectric strength, and primary inductance of 510.3 mH (5.70K ohms) with halves joined or 1.924 H (19.40K ohms) in series, with leakage inductance of 490 uH and 1.961 mH respectively.

The drawing describes a sealed case and epoxy-potted transformer for stable characteristics and long life (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). The drawing gives tolerances of ±0.063" on A, B and D, with C 1.65" max. The 850JA is RoHS and REACH compliant, with a listed shipping weight of 0.44 lbs (0.20 kg) and UNSPSC 39121301.