Hammond 142A 10K:10K Center-Tapped Open Frame PCB Audio Transformer

The 142A is a 142 Series open frame audio transformer for P.C. board mounting with 10K ohm center-tapped primary and secondary windings and a 1:1 turns ratio. The manufacturer lists it for driver, input, interstage and isolation applications, and the drawing adds impedance matching and pulse use, making it a fit for circuit designers who need signal-level isolation between 10K ohm stages.

The 142A handles a 100 mW power level from 200 Hz to 15 kHz, with frequency response within +/- 1 dB referenced at 1 kHz at both +10 dBm and +20 dBm. Maximum unbalanced primary D.C. current is 4 mA. Total distortion is less than 0.5% for outputs at 200 Hz, decreasing at higher frequencies, and insertion loss is less than 1/2 dB. Because the windings match, the secondary may be used as the primary and the primary as the secondary.

Total winding D.C. resistance is 720 ohms primary and 925 ohms secondary (+/- 15% in the series table; the drawing lists the same values at ±20%). Typical inductance is 14.0 H on both the primary (pins 1-3) and secondary (pins 4-6) at 1.0 kHz, 1.0 V, with 68 kΩ impedance on each and 1.25 H leakage inductance.

Construction is economical and open type, with pin terminals (0.0375" x .02") on pin bobbins set to a standard 0.187" grid pin spacing for P.C. board mounting. The windings are bifilar wound for balanced capacitive and resistance characteristics, and the insulation test is 1500 V rms. Net weight is 0.5 oz. Dielectric strength is 1500 Vrms, operating temperature is -40 to 85 °C and storage temperature is -40 to 105 °C. The 142A is RoHS and REACH compliant.