The UBT-1 from One Electron is a low-impedance single-ended output transformer intended for parallel combinations of tubes running a B+ voltages of 250 to 325 volts, such as: two or three EL34s (triode connected), three 2A3s, two 300Bs, two 6AS7s, etc., as well as single sweep tubes run in 'enhanced-triode' mode, resulting in 10 to 15 watts of output power. It features a paper bobbin. The UBT-1s low impedance gives an exceptionally broad frequency range of 10Hz to over 75 KHz (at 1 watt). This transformer has been the basis for excellent-sounding single-ended amps, and is notable for its clean, detailed sound. 6.1 lbs.