This worries me a bit to hear, although I am no bass freak, I like tight bass, using a solid state power amp instead of tube power amp make any difference?'Tight bass' isn't natural bass, FWIW. It usually occurs in stereo systems where the woofer is overdamped. 6SN7s have no worries playing bass- no tube does- any tube can go to DC.
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IME/IMO, the worst of the 6SN7s are as good as the best of the miniature tubes. When you get a good 6SN7 no miniature tube competes. We use 6SN7s in all our preamps. We used to use miniatures in our amps decades ago, but when I discovered that 6SN7s were back in production, we switched over to them and never looked back.
Microphonics can be an issue, but that is true of all the miniature tubes too- in particular the 6DJ8/6922 family. BTW, the 12AU7 and 6CG7 are based on the 6SN7. The latter is literally a 6SN7 in a mini envelope; the former has half the plate area but similar geometry and so acts very similar on paper, but neither sound as good as the real thing.
Andy Bowman has been supplying our customers with good tubes for a long time.
We've been getting feedback on the TJ Music, Black Treasure Psvane and Sophia. They are universally liked, in particular the former two; with comments like "the best of all the NOS tubes rolled into one without the weaknesses". That's a pretty serious statement- but we hear it a lot. We have found though that the Sophias have been short-lived in comparison.