I had to repost this from a reply I did/ Swart amps are awesome! Hi, Let me tell you something. I purchased the AST used about 2 months ago and never thought this amp would sneak up on me like this. It has some of the best and harmonically rich cleans I ever heard. I did some tweaks that made the amp twice as good in my opinion and everyone who plays it opinion. I first put in all NOS tubes and changed a few values. I dropped the GZ34 to a 5Y3 40's blackplate (cheap and easy to find. This gave the amp more cleans and opened it up some more. Next in V1 I put a RCA 12AX7 which gave me more of everything WOW! what a change. Next in the reverb driver and return a RCA 5751. This hits the tank harder on the dwell side and is a little easier on the reverb return which makes the reverb sound much better. The last tube use a good strong NOS 12AX7. The amp went from good to great. The last change was to get rid of the boxy sound. I swapped a G12H30 into this and it transformed it to the top of the heap for sure. This suggestion was made by RYHLICK to me, my tone buddy who lives in a parallel tone universe with me. More of everything and for some strange reason the speaker baffle sounds twice as big and the cab sounds huge now. The G12h30 also has much more touch sensitivity to. I have played against a Guy with a blackface 2 6L6 and had no trouble keeping up. As setup this amp is killer. The trem is the best out there. Very good reverb now and some of the best cleans tones with my Tele that I have ever experienced. It also still overdrives very nicely, actually more controllable and predictable now. You could also step up the drive a little with a 5V4 rectifier . Michael had told me the original AST used a 5Y3 and he loved it, but new good choices were not available for building his amps. This amp is a jewel and a lucky find for anyone. Try this tube setup and speaker and don't look back. This amp is like a supro, vox, blackface and a touch of tweed all rolled into one.