The UBT-2 from One Electron is the same size and power (15 watts) as the UBT-1, but has a higher primary impedance suitable for single tubes running at B+ voltages of 400 to 500 volts, such as: 50, WE 300B,etc. It features a paper bobbin. The trade-off of a higher impedance transformer is worse bandwidth, but additional interleaving was added in the UBT-2 to extend the frequency range from 10 Hz to over 55 KHz (at 1 watt). The UBT-2 has also been successfully used as a choke load for shunt-feed output stages. Plate supply voltages over 600 volts are not recommended. 6.0 lbs.