Hi, I am having trouble with my setup and looking for some help/suggestions. I recently set up my Bose 901 VI’s that I haven’t used in quite some time. They are hooked up to an Adcom 555 amp, Adcom GTP-400 preamp and Bose EQ. The issue is intermittent but I am getting a crackling/low muffled sound out of the left speaker. I thought it may be the RCA to 1/4 cable that I was using so I got a Bluetooth receiver. The issue still happens. I tried using all RCA’s on the preamp (tape 1, 2, CD) and same issue. Any idea of what’s going on? I appreciate any help.