((( I’ve been using a Belles 21a tube pre))) Why not check out the new Belles Virtuoso power amp? It has dual mono transformers sophisticated power supply, friendly 100 k input impedance, gain matches your existing Belles preamp, performs beyond expectation and its not digital. Please excuse my phone camera action
Best JohnnyR Belles Dealer
https://www.youtube.com/watch?v=BSyZuSyO76M