Markus - based on many reviews on both the Sachs and Supratek I believe you’re going to be happy one way or another. I’ve experimented with many high quality preamps with different tube configurations, and to me the 6sN7 is king, and not by a small amount. So cool that there were so many great tubes that were produced over the years you have many tube rolling options. Most are reasonably priced (comparatively speaking) though my favourite in most cases is the 40s TungmSols. These are not cheep, however RCAs from the 50s are plentiful, inexpensive and sound great.
i have the pleasure of owning some other 6SN7 based Pre’s not on your short list and can confirm when a designer does a good job of it, the results are stellar. With each brings its house sound the the pros and cons that go with it. Further system synergy is so important, with all the tube rolling possibilities, you should be able to find your nirvana with either.
i hope someone can chime in and provide a candid comparison with the Sachs and Supratek from the same system... I would love know too!
i have a Supratek Chenin. Great preamp, and I love the dynamics it has. Mick is spot on here. I own a Modright LS100. (Supratek, is easily better to my ears).I have an Antique Sound Lab Flora, another one that is very good along with an Wyetech Opal, stella preamp! (Not in the same price category) The Opal betters the Supratek and ASL (my systems, ears and sonic priorities) if anyone in the Toronto Canada area has a Sachs, bring it over and we could have a comparison and I would be happy to report the findings.
Other 6SN7 preamps I’ve been curious about and would welcome a chance to hear in my system included; deHavaland Ultraverbe, Atma-Sphere MP-3, and TRL Dude.
Either of the two on your list have a plethora of universal praise from many well regarded forum members, I think you cant make a bad choice here, though it would be optimal to listen to both in your system before you purchase. All the best with your journey!