The neck, like its clean tones, is nice and thick and fat under gain, but hasnt sounded muddy to me yet. It sings on the high gain settings and really sustains well. Likewise the middle position has a little bit of that airy open feel to it (like its clean tone surprise surprise), and is great for the lower to medium gain stuff...for example i was jamming to some SRV stuff with it and it had a great vibe to it for that kind of stuff, really brings your feel through in the sound i thought.
As for the bridge, the first thing i noticed as i said above was that it wasnt as thick as the JB in my jackson, but then i started fiddling around with my amp settings. While the burstbucker has a more open natural feel to it than the JB and a lower output, in the les paul because its such a better guitar it had a tone to it that i just liked better...but it didnt seem as thick still. Then i started playing some darkness on it and for the lead stuff put a small amount of extra distortion in the signal chain to turn on for solos from my dave ulbrick distortion pedal, and it just had a more authentic sound i guess than the JB jackson. I dont doubt that the jackson would still be a better guitar for all out metal and shred, but the burstbucker LP sounded much more like that real chunky les paul marshall vibe (surprise surprise) that i, like lots of you, have always loved! And even without the boost from the pedal it still sounded thick as with the right amount of gain and still got heaps of great singing harmonics...and with the boost...WOW...lookout Darkness! Im finding it hard to come up with the right words to describe it, but it sounded great! The easiest thing for me to compare it to right now (because i was jamming to them with it) is the darkness tones. Through my ENGL i got a really awesome darkness type rhythm and lead tone, and with the extra boost from my pedal i got an even creamier tone for all those thick darkness lead bits...but it wasnt as fuzzy as the darkness tone could sometimes be it was definitely smoother. It sounded huge, and i saw that even though the pickup wasnt as thick as a JB, with the right blend of amp and pedal gain i could get it sounding as thick as i wanted.
In conclusion for those who have bothered reading all the way to the end of this, i wont be rushing to swap out these pickups...they rock! (and jazz

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Thanks for reading, damn that took me ages to write!