The YJShort is shorter than the standard YJS converter, allowing for use in amps that do not have room for the standard converters. It is a specialized, current-limiting/voltage-conditioning adapter for use in most 20 to 100 watt amps which use 6L6, EL34, 6550 or 6V6 output tubes. All Yellow Jackets® converters come with JJ Brand EL84/6BQ5 vacuum tubes.
- All Yellow Jackets® converters come with JJ Brand EL84/6BQ5 vacuum tubes.
- Converts most audio amplifiers with 6L6s, EL34s, 6550s, or 6V6s and similar-based tubes to EL84s without modification or rebiasing.
- Converts: Class AB to Class A operation
- Drops Output Power: 50% to 70%.
- Safe for all common amplifiers and transformers.
Yellow Jackets® converters are a type of specialized adapter which permit the use of EL84/6BQ5 power tubes in place of 6V6, 6L6, EL34, and 7591 type vacuum 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!
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.
All Yellow Jackets® have a one year warranty against manufactured defects.
For more information, see Yellow Jackets TC
Specification Sheet 
480.296.0890
Product Reviews
I have a handmade (by an amp builder) JCM800 2204 clone that I use these in. The problem was that, to get power tube breakup with the EL34s, the amp had to be insanely loud. I tried multiple attenuators, and they all negativity effected the tone. So, I figured I'd give these a try.
I was a little hesitant at first to part ways with my beloved EL34s, but that was gone after I put the yellow jackets in and gave the amp a spin. It sounds great. I honestly stick out in the mix substantially more than I did before. I should note that I use Genalex Gold Lion reissue EL84s rather than the JJs that come with the yellow jackets.
All in all, this was a great purchase that allows power tube breakup at reasonable volumes.