The stock Harmonix 6sn7 pair analog output tube and the single Sovtek 5AR4 power tube that the Modwright Tube Mod includes is severely lack and this mod is ultra sensitive to tube rolling. I tried a Mullard NOS fat base and Synergy Create 5AR4 power tube. The Synergy was the best. I have one Synergy 5ar4 with 75 hours use and matching Herbie Audio damper. The Synergy Create 5ar4 power tube had the best dynamics, bass impact and overall balance. The Mullard was rolled off in the high frequencies.
The Synergy Create Nanotechnology 5ar4 is $60. The matching Herbie Audio Labs Ultrasonic Tube Dampers are $20 each (was $30 new).
