Tube Preamp with Solid State Amp?

Short answer, no, hardly any of them.  There are some DACs with both tubed and SS output stages but I cannot think of a single preamp, although I suspect there is one somewhere.  Of the several tubed preamps I have owned, and even the hybrid Lamm amplifiers I have owned, none of them provided what I would consider a tubed sound as you would get with most tubed amplifiers.  As I indicated to the OP earlier in the thread, IME, if you want a tube-type sound, get a tubed amplifier. 

While I have long been a fan of heavy Class A amps that never seem to run out of steam, I have actually gone all tube in my main system and really like it.

I also had tube pre and SS power for a bit. Either can work but it is system dependent and the only way to tell if you prefer it is to give it a try.  You can always sell whichever you like less.

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.