good preamp for First Watt F7

As it is, I routinely use the the F7 with a B1 which has no voltage gain, but my sources have 2V or more.

A lower output impedance than the B1’s 1kohm "may" sound better into the F7’s 10kohm
Maybe trial (14days) the $299 active unity gain Saga-S or one of the others, you can have active tube/solid state or passive and remote. Send it back if not happy
https://www.schiit.com/products/saga-s
Cheers George

bakalovb OP

You need a little gain also with the F7 being only 14db.
Just go with the Schiit Freya-S or Freya-+ both have 75ohm output impedance on rca on their active stages and a gain of 4, and should drive the F7 no problem. Stay away from the Schiit Saga's as they are only unity gain.  

Cheers George