I 2nd the MODWRIGHT , LS100, or the 36.5 with the external tube based power supply. These preamps will add incredible detail and a very beautiful tone... especially guitar strings. I use a older SWL 9.0 sig edition. I love the tubes in this thing! I have a Mullard 5AR4 rectifier. and 2 rare 5687's from RCA.This unit drives my beast ,a McIntosh MC352 power Amp. Good luck man!