came with groove tubes..12AX7R. the 12AU7 is electro-harmonex. I've got extra tubes as follows: two electro-harmonex 12AX7 two sovtek 12AX7LPS although used a few times, they weren't used hard and i'd like to put them in this amp. anyone got any suggestions as to a particular order for installing these? the amp sounds good, i just want it to sound better and i know these are good tubes. i know there's better tubes out there, but these will have to do. tube guys, psychobassguy, thanks for your help in advance.