Hammond 125B 5 W Universal Push-Pull Output, Flying Secondary Leads

The 125B is a 5 watt universal push-pull "classic" tube output transformer for general purpose or replacement use (not Hi-Fi). It serves technicians repairing vintage radios and amplifiers and builders who need a single output transformer that covers a wide range of plate loads and speakers.

Unlike the other 125A-125E models, which use secondary solder lugs, the 125B brings its secondary out on colour-coded leads at least 5 inches long: BLK (1), ORG (2), GRN (3), YEL (4), VIO (5) and WHT (6). Choosing a pair of these taps gives a resulting primary impedance from 1,200 to 25,000 ohms (blue to brown) with 1.5 to 15 ohm speakers. For instance, an 8 ohm speaker on taps 4&6 reflects 12,800 ohms, and a 4 ohm speaker on 2&5 reflects 4,100 ohms.

The 125B carries up to 35 mA DC bias per side, with a primary inductance of 8.97 H in the ordering table. Typical drawing data shows 296 ohms primary DCR (blue - brown), 3.70 H primary inductance and 16.7 kOhm primary impedance at 1 kHz, 1 V, 1500 Vrms dielectric strength and a temperature range up to 105C. Typical response is 1.0 dB from 100 Hz to 15 kHz; the series rating is 150 Hz - 15 kHz at full power (+/- 1 dB, ref. 1 kHz).

It is an open style transformer with minimum 5 inch primary leads (BLU plate, RED B+, BRN plate). Overall dimensions are A 2.38 in (60 mm), B 1.38 in (35 mm), C 1.38 in (35 mm) and D 2.00 in (51 mm) with 0.19 in (5 mm) mounting holes; weight is 0.3 lbs (0.14 kg). It is made in Canada and is RoHS and REACH compliant.