McIntosh reference preamp C12000

On the C-12000 remote the input on the left side of the remote.  On the read out on the control unit, depress until you get to the desired input be it tube in input 2 or solid state input 4. You can label inputs as well

bernardwilliams, So you are not using the MEN220 before C12000 preamp in your system? 

On my C12000 I can’t hear a difference between the Tube and Solid State settings as used through the RCA main out.  When I set it up through balanced XLRs then I can hear a difference.  
 

C12000 owners can you help me?  I am wondering

if my unit is defective or if this is normal??  
 

Thanks in advance for any insight!