Hammond 1650W 280W Push-Pull Parallel Output Transformer, 1.9K CT

At 280 W, the 1650W is the highest-power model in the series: a push-pull tube output transformer with a 1,900 ohm centre-tapped primary, 806 mA DC per side and 4, 8 and 16 ohm secondaries. It is listed for push-pull parallel operation with 6 or 8 tubes, with suggested types 6L6GC, 5881, EL34, 6550B and KT88, and uses a larger frame and larger mounting slot than the rest of the range.

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 4.38 in (111 mm), B 7.50 in (191 mm), C 5.25 in (133 mm), D 3.50 in (89 mm) and E 5.88 in (149 mm), with 0.20 x 0.38 in (table) / Ø0.275 x 0.615 in (drawing) mounting slots. Typical electrical data from the drawing includes a primary inductance of 122H / 63KOhm, leakage inductance of 3.56mH, a dielectric strength of 1500Vrms and a temperature range of -40 to 105C. Shipping weight is 28 lbs (12.70 kg).

The 1650W 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.