Jens played leads on Winterheart's Guild album songs on The Cage, Silver Tongue, Victoria's Secret and Champagne Bath with Roland JV-series sound module. Keyboards other than leads on those songs were played by Tony Kakko with Korg Triton. [1]
Jens wrote about his late 90's Stratovarius gear on his homepage [2]
"After joining Stratovarius in 1995, the only new piece of equipment I've gotten is the 1080, which works very nicely for that sort of music, and more spare controllers in the shape of DX7:s, which is what tends to break, nowadays. I briefly tried to tour using a P6 with strato but it broke a couple of times too many. On Episode, I used the M12, a P6, the Finnvox Yamaha grand, the DS330, and Kotipelto's O5RW. Possibly some other piece of machinery from Finnvox as well, I can't remember now. (A Korg Wavestation?) On Visions and Destiny, I made heavy use of the 1080, the Finnvox grand, and the trusty old P6."
"For the strato tours I've used, in order: Polysix with DS330, Polysix with 1080, DX7 with 1080. The solo effects have been: Korg PME40 until that got stolen in Madrid together with my first 1080, some shitty Spanish distortion box that the guy in the store in Madrid gave me when I bought my present 1080, and presently a Morley JD-10 speaker simulator which is great."
From Infinite album onwards he used the Roland 1080 for leads instead of Polysix like before (judging how it sounds leads are different from Destiny). On Eagleheart music video there is 01/WFD, but I think it's only "prop" just for the video.
In 2002 Jens posted pictures on his website from Elements recording sessions, which included a picture of his equipment. From top to bottom: Roland JV-1010 sound module, Apogee Rosetta Ad A/D converter, Morley JD-10 distortion on the side, Digitech DSR-24 effects, Roland JV-2080 sound module, Emu Proteus FX sound module, Roland JV-1080 sound module and Roland A-37 midi controller. [5]
Live he continued to use Yamaha DX7 with JV-1080 during the 2000's and around 2010 switching from Yamaha DX7 mark I to DX7 mark II.
In 2013 he added a tiny Akai MP25 on top of Dx7[3] and started using a laptop for sounds. The songs on Nemesis have complex sounds made with VST plugins and some electronic music sounds using an arpeggiator control requiring the Akai.
Later he switched to use Roland A-800 Pro as midi controller.[4]