I'm on a few different guitar discussion groups on facebook, and in the comments of a post i recognised a name that I had seen earlier.
Antti Härmä. He was Alexi and Roopes tech from 2010 till 2014. He built the initial Marshall rig using 3 JVM410H for Alexi.
Prior to going with the Marshalls, Alexi tested out some stuff:
"There was a period when some soul searching was done when it comes to tone. The Lee Jackson, ADA MP-1 and Engl E530 were circulated until he settled for the Engl and a VHT 2:90:2 power amp. The Engl Poewer amp they sent us to try out didn't work out, it was straight up Norwegian black metal territory. Blackstars were tried out too but they never made the touring lineup for even a single gig. Then around Halo he told me he wants to play Marshall so I started the
negotiations and he got an endorsement."
And:
"The E530 was gigged extensively and it was also in the US rig. The MP-1 was around for a few shows, it never really worked out.
The marshall rig was simple and fail safe, it had two identical head running simultaneously that were switched with a Weber amp head switcher. And a third one running a very loud offstage can that few the FOH.
RRF was Lee Jackson for Allu. I think Roope had the Engl then already."
And finally:
"The wireless units were Sennheiser EW500 G3s. The reference cable I built for them was a Mogami 2524 with Neutrik connectors. When we got the Sennheisers they had dialed in their sounds and we'd just sit and try to match the sound with the wireless. We got pretty close, but the lower mids were always behaving differently with the wireless. Still, close enough with the gain settings and the cable emulator. I think we ran the packs at -42dB or -39dB and the output of the receiver at +18dB. The pickups were passive EMG HZ-2s, which are not super hot. I think the preamps were run at full blast except for the volume. All new guitars were volume matched so there was unity gain between them, of course.
The Lee Jacksons were modified for more gain by a Finnish amp wizard Lassi Ukkonen, a former military helicopter tech. He still is doing amp stuff, his company is called Triodipaja. He knows the exact details of the mods, it wasn't anything complicated, though.
You will get the live sound of that era pretty much by running the E530 into a VHT 2 90 2 power amp and a straight Marshall 4x12 loaded with V30s. There are no big secrets there."
Those wireless units cost half as much as one of the amp heads. I think them being high quality, and much more adjustable than the cheapo 2.4 gHz systems around, means that you can gain match what the guitar-preamp was supposed to output to the Marshall/rack preamps. Studio was always a cable though. Other than that the rigs were dead simple. Antti also appears in the 2013 rig rundown that is on youtube.