Contact PartsConnexion up in Canada. The name escapes me at the moment. But he used to own and run Sonic Frontiers. He still offer services and upgrades for SF gears. He should be able to provide you with an answer.
Yes, I've had a Line 3 SE for many years, it's phenomenal and IMHO a bargain for what it delivers. It does most everything extremely well: accuracy, soundstage, frequency extremes including a lucid midrange... it's also neutral almost to a fault so you can add your own favorite dash of flavor with tube choices, I/C's, speaker cables, and to a lesser degree: power cables as well. It's an overachiever when originally new and a steal at today's used market prices (plus it can still be fully serviced if/as ever required). Good luck.
Disclosure - I own an Line 3 SE!
After having had many preamps in my system, the Line 3 has become my reference preamp. For the eagle eyed you will see I currently have an ARC Ref3 up for sale ..... I think that says it. IMHO you will never need an upgrade and Chris Johnson at PCX is an invaluable resource should one need tech support. Chris maintains that the Line 3 has circuit design IP that has never been repeated - who knows, but it is both faithful and musical to the source and equally important very compatible with both SS and tube power amp loadings via the impedance curve - not always the case with other preamps if you are mix & match.
The SE+ upgrade plus the replacement volume chip / power supply is the ultimate upgrade to reach world class reference performance.
As time marches on, so do circuit designs. The Line 3 is still a venerable design, still supported and still world class. I did move on to an MBL 6010D and for a lot more $$$ I did get a preamp that had more synergy with my Spectron amps and probably a lower noise floor. But in absolute terms the Line 3 is still one of the better tubed preamps out there for "straightwire" gain with good flexibility, low noise and the ability to roll tubes to change tone ever so slightly.
What about the digital volume control? I heard the ICs go out and are not replaceable then the preamp is done. I heard allot of those are now failing, as they are nearing the end of their usefull life.
I have a SF preamp and it had a nasty habit of going to full volume in one channel- exciting, but not for me.
01-06-10: 6550cThere is a digital volume control IC upgrade/replacement offered by Chris Johnson at Parts Connexion(official SF repair/mod house). The IC upgrade has been available for at least a few years now and supposedly provides a significant improvement in sound.