[1]
[1]This model of Yellow Jackets® converter, the YJ7591, is a specialized, current-limiting/voltage-conditioning adapter for use in most amplifiers which use 7591 output tubes.
Yellow Jackets® converters allow you to harness the musicality of EL84 vacuum tubes in amps that don't use them already - it's like getting a whole new amplifier! In place of a 6V6 a Yellow Jackets® converter will even out the tone and make it sound stronger. In larger amps that use two 6L6, 6550, 7027 or EL34 power tubes the Yellow Jackets® converter will drop the output power to about 15 to 20 watts, giving it more of a vintage VOX AC30 sound. In amps that take four power tubes the Yellow Jackets® converter will sweeten the tone and make it more dynamic. There is no rebiasing involved, which makes modifying your amp's tone very easy.
Yellow Jackets® converters give you simple Class-A operation from any amp. They not only rearrange the pin locations of the tubes, but also provide the necessary plate voltage drop and current limiting on the screens as well as blocking the amplifier's grid bias voltage while configuring the EL84 in a Class-A, self-adjusting cathode-bias circuit. In other words, there are no adjustments to make and no modifications necessary, you simply plug the Yellow Jackets® into the amp's output tube sockets, (in cathode-bias amplifiers) screw the ground wires under one of the output tube socket mounting screws, plug the provided EL84s into the Yellow Jackets® converters, turn on the amp and play.
