Hammond 1645 30W Push-Pull Output Transformer, 5K CT, 70V Tap

The 1645 is a 30 W push-pull tube output transformer with a 5,000 ohm centre-tapped primary, 128 mA DC per side and a secondary offering 4, 8 and 16 ohm taps plus a 70V line output. That 70V option sets it apart in the range, letting one transformer drive either conventional speakers or a 70V distributed audio line from a two-tube push-pull stage using the 6L6GC, 6V6, 807, 5881 or EL34.

Construction follows the classic series design: the transformer is enclosed (shielded), with 4 slot, above chassis Type "X" mounting, plastic coil forms for coil support and insulation, and insulated flexible leads (8 in minimum per the part drawing). Frequency response is 30 Hz to 30 kHz at full rated power, +/- 1 db max (ref. 1 kHz) minimum. Because of the unique interleaving of the windings, both secondary windings must be engaged to meet specifications.

Dimensions from the series table are A 2.50 in (64 mm), B 3.75 in (95 mm), C 3.06 in (78 mm), D 2.00 in (51 mm) and E 2.69 in (68 mm), with 0.20 x 0.38 in mounting slots. Typical electrical data from the drawing includes a primary inductance of 180H / 82KOhm, leakage inductance of 5.0mH, a dielectric strength of 2000Vrms and a temperature range of -40 to 105C. Shipping weight is 4.5 lbs (2.04 kg).

The 1645 label is marked Made in Canada, and the part is REACH and RoHS compliant. The manufacturer notes that tube operating conditions change the optimum plate-to-plate load, so consult a tube manual or data sheet before choosing an output transformer.