Re: yellow jackets
Well, I have used them in a few amps -
My take - they are only useful if they fulfill the tone type the amp needs/lacks such as MORE grease, more of that Class A / EL34 kinda sponge. They give every amp a Vox kinda mojo.
I have talked to THD many times about these. You can use them in almost any amp, just call them and talk to Ed. I believe it only matters if the amp is Cathode biased - then you might need different THD's.
In my Mark IIb, the Yellow jackets worked very well BUT I DID NOT like them. Took away from the very perfect Mesa clean channel.
On my 73 Marshall, it was like a Marshall meets a Vox - a la Budda, but better! However, you have to really listen to the harmonic structure. If the amp isn't getting the gorgeous overtones you seek, it's not for you. If you want it for attenuation and feel, you might love it. I do not use them right now because I record with this amp and I need the REAL plexi tone that JJ's and Ruby's give me when cranked. El84s aren't the same.
Downside? Mixed with EL34's in the Marshall, I felt there was a nice thick compression, but the mids got kinda harsh. It hurt my own ears when playing. I always know an amp isn't right if it actually makes my ears sore. Marshalls have more than enough rude mids without help from YJ's.
In the Heartbreaker, the clean channel has a nice break to it, asnd the YJ's work well with that. The 6L6 gives very typical 6L6 distortion in the Marshall channel, so I felt the YJ's mixed well. In 60w mode, only the outside tubes work so it was like having a 15w class A amp, and when cranked in 100w mode well you got something huge.
They sounded nice and greasy in my Rivera Knucklehead series 1.
Best part - it's a cheap investment to experiment.
You never know what you will get.
