I am copying a post from the VR forum, just wondered if we could get a PRS response - thanks!
I measured the DC resistance of my 408 pickups at the end of a guitar cable and they read 500k(!) compared to the usual 8.5k of a PAF. Most guitar amps aren't designed to work with that kind of input - it's like using a veeeeeeeeeeeeery long guitar lead.
Always use a buffer! Either a non-true-bypass pedal (any Boss pedal for example) or something that's always on (EP Booster, OD etc). The output from the pedal or the buffer will output a more normal signal for the amp to receive.
408s straight into my 65 Amps London Pro, for example, sound really dull and flabby. A buffer maintains the clarity that makes these pickups so good