I think an Ultraverve by Dehavilland (Kara Chaffee) would meet the description in your original post. It is 6SN7 based. I bought a used one here on Agon and sold my Primaluna Prologue Premium that I had for 5 years. The PL served me well, I was just after a full, neutral, non-colored, i.e. different sound. I was amazed at the impact a different preamp made in my system.