Krell FPB 700CX

@invalid  It may have to do with the protection circuitry. 

If you don't have a blocking capacitor it's a good idea to have some sort of amp and speaker protection circuitry.  Either detect DC and disconnect the inputs and outputs or adjust the bias to compensate. 

Of course, all of this flies in the face of audio purism, so manufacturers have different ideas about whether to incorporate these or not.

My Krell FPB600 ran fine without the jumpers, with Aesthetix Io as preamp, no problem. But turning the preamp and let it stabilize before the amp is good practice.

I check my FPB300cx owners manual and sorry but no instructions given except have the mfg. the work.

What tube preamp are you going to use with the Krell amplifier?

Appreciate your question, but the answer I am looking for is what jumpers JMP1? Is needed to put capacitors in path to potentially protect against DC. SS or Tube may or may not leak DC, that's not the question, however.