These are easy and fun amps to upgrade by yourself. And, the designer of the ASL amplifiers ,Joseph Lau, is a great guy who even told me how to acquire a bit more gain from my ASL's because I use a passive preamp directly between the amps and my source. Fred, Run don't walk and purchase two very good NOS 6SN7's to replace the first (toward the front of the amps) of the three 6SN7's in each amplifier. The difference is HUGE! I replaced all other 6SN7's with vintage NOS as well but never came close to the sonic upgrade derived from replacing that first tube. I'm confident (fairly)that the use of Teflon coupling caps and expensive solid silver input cables also made a positive upgrade in my amps ,but, not close to that from replacing one 6SN7 with a very good NOS one. As said before, I replaced my AQ1006 DT's with a pair of Wavelength PF Gemini amplifiers which are fitted with 45's and offer yet more detail but the ASL amps had a bloom and a nostagic glow that I truely miss.

Lance A.