What is the difference between EMG actives and EMG passives?

Also, which would be better for clean or little distortion, as in classic rock.
92% of teens have moved to rap. I am one of the 8% that listens to real music.
The EMG 85 or 60 would be acceptable for classic rock/cleaner tones, but there are probably better options out there.

As for the differences, actives definitely give a much higher output than passives, but major tonal changes would be noticeable only if you have the right amp to back it all up. And from what I've heard from some people, passive EMGs are kind of muddy-sounding. Can't say for sure, I've only played EMG actives.
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