Vacuum Tube Preamp for Solid State Power Amp Pairing

Spatial Audio Labs "Raven" preamp. Really good!

I might get attacked for this, but I am very happy with my McIntosh C220 tube (actually a hybrid design) preamp paired with my Arion Audio S500 class D amplifier.  McIntosh has its fans and it's detractors, but I love the thing.  One great quality of McIntosh tube preamps is that the outputs are good for long cable runs.  This allowed me to keep the amp closer to the speakers with shorter speaker cable runs.  Not all tube preamps will work well with long output cable runs.  To me, I get just enough tube warmth to mate with my clean and neutral ss amp.  No longer in production, used C220 preamps are widely available.  Check out Audio Classics.

Audio Research SP-3-1A. Classic!

Linear Tube Audio Micro Zotl mk2 

a great preamp and easy on tubes  check it out.

     Tube gear tends to vary more in sound than do solid state gear.  Different design, tube types employed, etc. have a bigger impact than differences in parts and design of good solid state gear—an Audio Note linestage will sound very different from an Audio Research linestage, for example. If you can, you should audition each candidate, and preferably in your system.  
     Trying different brands of tubes (tube rolling) is not something you must do, but, if after becoming familiar with your linestage, you wish to explore changes in the sound, tube rolling is an opportunity not afforded owners of solid state gear (no transistor rolling).

     You should be able to find tube gear with all of the features you like.  If balance control is not on your list, you might consider including it.  Tube gear can develop imbalances (a tube getting weak, tube socket getting dirty, etc.) that, if minor, can be dealt with by a balance control until it gets severe or you decide to chase down the cause.

:You have a good budget.  A used Conrad Johnson preamp with a remote for volume would be another good choice.      CJ Premier 14 or later have remote volume

Check out a VTL TL-2.5.  I have owned one for many years and sounds good with a solid state amp.

Oops, right. No tube biasing!

Let's not make this too complicated. You don't bias preamp tubes. Tube rolling is not a requirement. In my fifty years I have never thought about electrical compatibility between a preamp and amp and had a problem. So, I would choose a preamp for its sonic appeal and just do a quick check on compatibility. 

Lot of folks like the PS audio and it is in a different league  than the Schiit. 

There's a lot more to consider also.

How many tubes, ease of tube biasing, type of tubes, tube rolling, new or nos...

I wasn’t aware of this, thank you for your advice @larryi  @viridian  

The sonic result of using a tube linestage feeding a solid state amp can be a little more unpredictable than solid state feeding solid state.  You should research impedance matching between linestages and amps.  The ideal electrical match would be a low output impedance of the linestage feeding a very high input impedance of the amp. Tube linestages tend to have higher output impedances and solid state amps tend to have lower input impedances meaning that there might be an electrical mismatch that will hurt the sound.  Supposedly, the input impedances of the amp should be at least ten times the output impedances of the linestage to avoid such mismatch.  But, even where there is no electrical mismatch, I have found that the sonic result of such a marriage is a bit unpredictable—a really good tube linestages may not sound very good with cerain solid state amps.

There are some practical considerations you should also consider.  Tube gear should not be left on all the time, while some people leave solid state gear on all of the time (solid state gear takes much longer to warm up and sound good which is why some keep it on).  If you intend on turning your tube linestage off or on while the amp remains on, you need to know if the linestage will emit loud noises while going through turn on and turn off.  If it does, you may be forced to turn off your amp each time you end a listening session and you turn off the linestage.