The single stage tube preamp is a very simple and good performing preamp but it will not drive heavy loads. It likes to see impedances of 250K or there abouts.To drive a tube amp I built with a interstage tranni front end I added a Pass BoZ single stage jFET preamp to the tube preamp. A BoZ will work into 400ohms and can provide large voltage swings.
A friend bought that preamp and wants another. This time I'm gong to add a Pass B1 jFET buffer
to the back end of a 4S tube preamps
. Look on this forum for threads about the two. The 4S I'm building is the MKIII which Suncalc designed and I re-named "The Black". I'm building all parts as separate modules; PS, B1 buffer, tube preamp, PS for the buffer etc. I have a dark wooden box with a lid in which all modules will be mounted the wired together.
So far I have the tube PS (250V) and the buffer complete. A 250K alps blue velvet will sit between the tube preamp and buffer. I have built a B1 some years back and this was followed by a number of BoZ builds. I always felt the B1 sounded better than the BoZs but the B1 has no gain and all my amps require a high gain preamp. In this case the single stage tube preamp will provide all the gain I require and now the ability to drive low impedance SS amps etc. images to follow.