Same here, I've never had this problem with any of the various Leslies I've been micing the past 20 years. There can be lots of noises, including bearing noises which might be misinterpreted though. It's hard to tell without being there and hearing the beast. As suggested, If you have a condenser mic without transformer (so that there can't be any magnetic pickup) you could swap that for the SM57 and see if the noise disapears - just to make sure you're not chasing ghosts.Brian Roth said:crappy mic preamp?
Been micing 122 and 147 Leslies for decades.....never had that prob...but willing to learn.