[Elecraft] K3 - S Meter query

[Stewart Baker]

I have my K3 S meter set on Absolute Mode as I like S9 to be 50uV 
whether the Pre Amp is switched in or not.

I would have though that with no signal into the K3 the S meter 
should read S0 with or without the Pre Amp.
Mine reads S2 with the Pre Amp switched OFF.
It also reads S4 if the Pre Amp = OFF, and the Atten  = ON.

Surely my K3 can't be that noisy as to give a S4 meter reading 
with no input, on all bands  ?

Please someone help me resolve this on a very wet British Bank 
Holiday !!

73
Stewart G3RXQ