ACORNIC did an excellent review of this amp in this thread with meticulous detail regarding tubes. I found similar results to his with tube rolling. The general consensus is that this amp benefits from tube rolling. His review will provide general impressions of different tubes in both driver and rectifier positions. I strongly recommend you check it out and get some cheap tubes to drop in there. Then when you start to notice the difference, you can search for your "best sound" tubes. I use relatively recent Tung-Sol US made 6SN7s and an RCA coke bottle 5R4 and I am happy with it. Electro Harmonix 6SN7s sound good in it too.