For starters, I changed out the ECC's that were in it with two Sovtek LPS tubes for a thicker gain.
Still holding on to my crisp highs. I run it through a Rocktron Velocity 150 and use an Alesis MEQ-230 for tonal control. If you really want to have a big sound, that setup does it. My distortion is wicked and the punch is awesome. I do think that the MEQ-230 is the biggest reason for what I get, but I have always loved the tone of a marshall amp. I wanted rack gear, so I purchased this one used and have no desire to replace it. The unit makes no noticeable noise and I play loud as h$#^!! because I have a drummer and bassist that compete to see who can be louder. All in the fun of it...
Primarily I play Hard rock, from Iron Maiden to Shinedown, and Metallica to KillSwitch... , so versatility is not a problem. and to be able to change the tones and levels of distortion by a program switch is the best part, I don't have to remember knob presets and make the changes every time. ...or have to line up 12 different stomp boxes each for a different tone. Been there, done that and it makes a messy stage.
Never had a problem.......
I would love to have another for backup, but backup has been un-neccessary since this unit has been flawless. I have been complimented Several times on my tones and how "big-time" my sound is. As compared to other amps I have heard, I will stick with this pre-amp for a long time to come.