I use Yellow Jackets with my Dual Rectifier.
The scoop: The tone of the amp is altered, you may like it or you may not.
Cleans: Definitely much better. They chime and they are really bouncy and brown. The lack of headroom might be an issue though.
Gain: Different. More compressed and not as aggressive, mostly because of the huge power cut. They hit the sweet spot a hair sooner but it doesn't really make much of a difference from running 2 EL-34s / 6L6s on the spongy variac. The tonal quality of the amp is more vintage with less lows and more highs. I haven't found that the modern mode on the dual works whatsoever because the highs are too aggressive. If you are comparing two yellow jackets with four 6L6s on bold, you'll hear a gigantic difference in terms of power output and openness at low volumes. I'm assuming 4 EL-34s will be much the same.
Things I have had success with:
Marshall 1960ax 4 x 12 with greenbacks. The amp sounds SWEET with two yellow jackets running into one of these cabs. In THIS scenario, you get good tone at surprisingly low volumes. Keep in mind it sounds much more marshall-esque and you don't necessarily get that trademark recto tone. If you run modern high gain, it does sound pretty phat still. The best part is that the greenbacks thump instead of fart!
Thiele 2 x 12. (v30 / greenback) Sounds good, but not as good as the 4 x 12. I found the highs to be slightly over emphasized but when I was playing in a band situation, it sounds awesome. I prefer EL-34s with the thiele.
I haven't tried my Mock 212B with Yellow Jackets yet . . .
Things I have not had success with:
Mesa Rectocab. 15watts or so was not enough to drive 240watts worth of tight *** speakers. It sounded constipated and the Yellow Jackets would start to clip before the 4 x 12 would even start working. I mean if you are into that sort of thing, it might work but I didn't dig it at all. In fact, I thought I had wasted my money until I tried the little buggers in the Marshall 1960ax. That was definitely a =-o moment for me!
Advice: Try before you buy. They will alter your sound. Whether you like it or not is a personal thing and I can't inform you either way. Lets just say I use the Yellow Jackets sometimes, not all the time and I've been on this EL-34 thing lately.
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