Sadly, mine have developed and issue with the plug and I have lost sound in the right channel. I'll need to get it re-terminated which was something I've been thinking about doing already perhaps with balanced XRLs...
Hi, I just came across your post, on my search for a suitable amp for the K500. If you have not repaired your connection problem on the right side: I had the same problem on mine, and it is apparently a widespread yet harmless issue. Internally, the two cables are clipped onto the driver, and the connectors tend to loosen over time. All you have to do is lift off the piece where 'K500' is written on it (on the outside). It is glued on and comes off easily. Then you'll have access to one or two screws. Remove them and you can open the unit. You will see the cables. In my case I tightened the metal connectors, clipped them on again, remounted everything, and since then the right side works like a charm! You will find documentation on the web if you need a better description than mine. Good luck!