There are not usually line level points in the signal path of tube amps, unless you copy some amp from the return of an FX jack pair. Usual FX loop has a signal level drop to the send, then a boost back up to tube levels at the return.
Amps don't get much simpler than a PV Classic 60. Power tubes, phase inverter tube, input buffer tube.
Same with a Marshall 9005: two power tubes, phase inverter tube, buffer tube. They chose to do the phase splitting at low signal level THEN boost, but either way...