Rob, I think the RCA center conductor is wired in parallel with pin 2, the shorting pins short pin 1 and 3. I think the small silver piece he is talking about is the cable release. Krell amps come from the factory with the pins in I think? If the amp was new then Krell screwed up or if it was used, the former owner was running it balanced and may have lost the pins. You can bend a small nail to use as a pin if you had to I would think.
Dave
Dave