Hammond 125BSE 5 W Single Ended Tube Output Transformer, 45 mA

The 125BSE is a 5 watt universal single ended tube output transformer for general purpose or replacement use (not Hi-Fi). It serves amplifier builders and restorers working on single ended stages who want one part that covers common plate loads from 2,500 to 10,000 ohms and speakers from 4 to 32 ohms.

The 125BSE handles up to 45 mA of DC bias. Its core is butt stacked from 29M6 steel with an air gap to reduce D.C. core saturation, as used across the 125SE Series. The primary (BLU - BRN) reflects 10,000, 5,000 or 2,500 ohms according to the secondary lead used against the black common:

• WHT: 32 ohms at 10,000, 16 ohms at 5,000 or 8 ohms at 2,500 ohm primary
• YEL: 16 ohms at 10,000, 8 ohms at 5,000 or 4 ohms at 2,500
• GRN: 8 ohms at 10,000 or 4 ohms at 5,000
• ORG: 4 ohms at 10,000

Typical drawing values are 354 ohms primary DCR, 4.50 H primary inductance and 27.38 kOhm primary impedance at 1 kHz, 1 V. Secondary DCR runs from 300 milliohms (black - orange) to 798 milliohms (black - white). Frequency response is 100 Hz - 15 kHz at full rated power, dielectric strength is 1500 Vrms and the operating range is -40 to 105C.

Physically the 125BSE is an open style unit with primary and secondary leads at least 12 inches long, measuring A 3.25 in (83 mm), B 1.63 in (41 mm), C 2.00 in (51 mm) and D 2.81 in (71 mm) with 0.19 in (5 mm) mounting holes. It weighs 1.1 lbs (0.50 kg), is made in Canada and is RoHS and REACH compliant.