HipHopScribe
Headphoneus Supremus
Amazon: https://www.amazon.com/Genalex-Gold-Lion-E88CC-Tube/dp/B00D1DDKNM
The seller I bought mine from was Tonal Tubes, but they are currently backordered. I'm thinking I may actually buy an extra one or two of these since I really enjoy their sound and don't want to go too far down the tube rolling rabbit hole. Time will tell.... I also decided to replace my Fulla 2 with a Modi Multibit and that should be arriving in the next 2-3 days hopefully.
I'd be interested to know how much of a difference the Modi Multibit makes, I've been thinking about going down the same path