My TE Quatra Valve arrived tonight and I must say...WOW!!! This head just plain rocks and has tone to die for IMO. Wow, I just can't say it enough! It appears to be as loud as my RAH350SMX and it sounds beautiful through my 2x15 I have a couple of questions. First, the power tubes look to be fairly new. They are EH 6550 tubes that say made in Russia. Are these a good quality tube and are they just relabeled Sovteks? The preamps ofcourse are 12ax7 (ECC83) tubes. I can't tell what brand of tube they are. All that is on it is ECC83 in red lettering. Thats it. Any idea what they are? Thanks.