REPLACING TUBES IN ART PRE AND COMP.

[bc]

HAS ANYBODY REPLACED THE TUBES IN THE ART MP AND THE COMPRESSOR. IF SO, DOES IT CHANGE THE SOUND AND IN WHAT DIRECTION. WHAT BRAND SHOULD I GO FOR AND IS IT WORTH IT TO GET A LITTLE BRIGHTER AND CLEANER SOUND. I JUST FEEL LIKE EXPERIMENTING. THANKS

[l69]

Yeah, I made some discoveries there.
ART says the unit has two 12AX7 tubes in the Tube PAC but it really has only one Sovetek 12AX7 and one Phillips 12AT7. I was advised by TubeDepot.com the following:
"I would not advise replacing the 12AT7 with a 12AX7. They are different tubes. The 12AX7 has a Mu (Amplification Factor) of 100 where the 12AT7 is quite a bit lower."
I replaced the Sovetek 12AX7 with a JJ ECC83/12AX7 ($10), and noticed a bit more glistening of the high frequency. I tried the Mullard ECC83/12AX7 ($90), but didn't hear anything different over the stock tubes. Obviously, the unit itself didn't have what it takes to push the Mullards, as they are high-end tubes (which probably would sound good in an all tube amp, such as a fender Deluxe or Twin).
Needless to say, I no longer posses the ART unit. Not really much in the way of "sound improvement" for the money.