Hello. I have not been able to find a solution to my problem in other threads, so I thought I would give my own a try. I have a Kr-6600 that sounds fantastic (after Deox-ing pots and switches) but I'm experiencing a rather loud "pop" in the left speaker when switching between aux and phono 2 and Fm and phono 1. I have cleaned the sliding switches on the pre-amp board twice with Deoxit and Fader lube as well as all other pots and switches. I have set the bias on both channels (40mv) and reflowed any solder joints that looked even the least suspicious (this includes checking and re-soldering any obvious grounding points on the pre-amp board. I have also re-capped the pre-amp board with no real noticeable improvement of this issue. I have tried two different turntables and the pop is the same for both. One curious note, I did notice that, when I accidentaly plugged my CD player into the Phono inputs (on pause, thankfully!) the pop when switching sources was no longer there. Not sure where to look next, pre-amp transistors or power supply board? Any help would be most appreciated.