Ken uses Odyssey Stratos Mono (maybe the Extreme version?) and Mapletree Line 2A SE preamp with seperate PS module. All JPS SC3 signal wires, Black Sand power wires. Odyssey doesn't give the S/N spec on their website.
There are 2 common types of noise, hum and hiss. 60Hz hum comes from ground loop or EMI from transformer, and 120Hz hum comes from PS after rectifiers. Hiss comes from RFI, and all active circuit components (transistors and tubes) when they are powered on. You need to seal off the input jack on the amp before you listen for output hiss noise. Connect the preamp to the amp, but the preamp is not plugged in, nor is anything connected to it. This will stop any RFI getting into the amp input jack. Then listen for hiss at the speakers. It should be very quiet, if not silent. It should be fully warmed up also. There may be very soft hiss at the speaker, but you should not be able to hear any noise at all from your listening position, even in dead quiet room. If you can hear it from listening seat, call Klauss to discuss S/N ratio or repair options. Maybe it just needs bias adjusted. If something is broken or out of adjustment, then it should not be happening on both amps. If both amps sound identical, then it is the design. Decide if you can live with it. I never noticed any noise from them when I have visited your system, even with the horn loaded tweeter - and I am sensitive to it after living with tubes for so long.
But you should not hear any 60Hz hum from the amp with shorted input. If you hear hum with grounded input then it is either poor PS design allowing ripple on the DC rails (120Hz, not 60Hz) or poor internal layout where PS transformer magnetic leakage induces AC current on DC rails or signal wires, or else something is broken or out of adjustment. It's not poor design from Klauss, but he can give you better advice about what to try. It would be a good idea to test the amp noise with a ground buster on the outlet just to make sure it is not related to ground. Test each amp separately, and make sure they are fully warm.
Good luck!