Tube Preamp with Solid State Amp?

Let's not forget about matching impedance here. Tube power amps typically have higher input impedance, like 100K or so, and will accept any sort of output from a preamp, whereas solid the A21 has only 33K, so you will need a tube preamp with a fairly low output impedance, 3K or lower, prefereably much lower. Many modern tube preamps will work fine but some older ones maybe not. The classic Dyna PAS3-X specified matching to an amp with 100K or higher.

Have been mixing SS and tube for some time but the tube preamp and solid state amp is the least hassle. Tube power with all that heat, run away tubes, and bias adjustments is high maintenance.  I do it (run tube power) in the winter but more heat here May to October is no fun.  I have Audio by Van Alstine tube preamp and MOSFET power in an ancient Dynaco chassis.   I can even stand cd with this combination.  

The Pass XA30.8 input impedance is 100 K ohms balanced, and the input capacitance is just a few picofarads so anything will drive it.

I have a Rogue Metis pre with a SS Amp and love it. Very little noise. What tubes you choose does make a difference so you get to do a little tube rolling and that’s fun.