I was there a month ago and saw a nice looking audio shop near the slave market area. It was near Tommy Condon's restaurant on Church St., or it may have been around the corner on Queens St. I wasn't able to visit it due to time constraints, but the sign stated that they took appts., or you could take a chance and visit if someone was available. There was a guy there when I went by in mid-afternoon, but I resisted. Peeking through the glass, I saw a nice turntable perched on a far wall. It could be an interesting diversion if you are strolling the historic district.
Have fun...