hi!i ll speak about my "problem" with my rivera.ok its not so big but i want to improve him! the basic problem that i have is at the drive channel and not at the clean.(the clean is super,with crystal cleans and big bold notes.like a blackface but maybe with more modern voicing.more...hi-fi)! when i m on drive channel and i have the preamp volume at 2 (the maximum is at 10),its ok! but when i ll put the preamp volume at 4 or more its too ..buzzy,fuzzy etc..and i hate it!i hope you understood what i m saying!i must put down the preamp volume at 2! one guy that he had the same excactly problems he told me that everything solved when he changed ALL the preamp tubes.he told me that the worst sound that he had with this amp was when all the preamp tubes were sovtek,and these are the tubes that i have now!! he recommented me to put differend tube to its socket at the preamp and not the same mark if i understood correctly! he told me also that at first he thought that the problem was the 2 v30 speakers but he understood that was the 5 sovtek preamp tubes!i read this also at the rivera site.(about the problem with the 5 preamp sovtek tubes) i m playing this amp mostly at drive chanell and as a boost i m using one maxon od9 and one maxon sd9 distortion!i don t like the ninja boost of the amp at all!i prefer to boost the amp with my pedals that they sound better at the drive channel and not at the clean where they sound thin! just to know,usually i dont play with much gain! maybe one solution with big difference at the tone would be to change the one speaker.but i want first to .."play" with some tubes for ..experiment!i ve heard that this amp is very sensitive to tube changes . (i think like all the amps..). very general the tone i m looking after for is: with my strat suhr: >srv >gilmour >scott henderson (dog party,tore down house) with my les paul and tele: >robben ford >peter green >albert collins ====================================================================================== from rivera quiana manual i did copy paste this: Location Type V1 12AX7A V2 12AX7A V3 12AX7A V4 12AX7A V5 12AX7A V6 6L6GC V7 6L6GC Here's a brief description of what each tube does: V1 Input buffer and tone control driver for Channel 2, and also the first Preamp stage of Channel 1. V2 Tone control follower for Channel 2 and an additional gain stage for Channel 1. V3 Third gain stage for Channel 2 and for Channel 1 V4 Reverb follower gain stage, and mixer for both channels V5 Phase inverter driver tube for the power amp section V6-V7 Power amp tubes RCA built great ones as well as the best coming from Sylvania. There are only four factories in the world building this tube; Svetlana in St. Petersburg, Russia, Reflector (Sovtek) in Russia, JJ/Tesla in Slovenia, and a factory in China. NOS (New old stock) supplies from various other factories are still available, albeit in short supply. we have had the best success with the Svetlana, and some of the recent Chinese that are a copy of the Sylvania, sold by Ruby Tubes. In terms of 12AX7A types, there are only 3 factories that we know of building this tube type; JJ/Tesla, Sovtek, and Ruby Tubes in China. Again, NOS stocks still exist of RCA, G.E., Mullard, Telefunken, Sylvania, Mazda, and Philips. >Usually the Chinese sound the brightest and have the most gain. >Recently the Sovtek 12AX7LP has been made available and it is improved from it's predecessors, yet has less gain and less high end than the Chinese. >RCA, G.E. Philips, Mullard (NOS) are great tubes, but may need to be selected for microphonics. We are using mostly Chinese for the 12AX7A's, but we may use a Sovtek in position V1 only. If you use Sovtek, or JJ/Tesla in all of the positions (V1-V5), the amp will sound way too dark, and will lose gain and headroom. It will sound like a blanket was placed over the amp. so 5 preamp tubes that you recommend me? what tube to its socket? i dont care about the money. thanks for your time and sorry for the..big thread,but i want to find a solution!