I’m a former NAD owner, so know that house sound somewhat. They’ve generally got good dynamic range but with mediocre transparency using a lot of feedback. A tube preamp is not a bad idea running with lower tiered Solid State AB amps to inject some friendly 2nd harmonics to help override the 1st harmonic noise of less expensive components. It’s sort of like adding cream to acrid coffee but does help. I’d recommend a used Rogue Metis or the upgraded Metis Magnum ($700-1400). Then, I’d get a pair of 6f8g to 6sn7 adapters off eBay (~$20) and some NOS or lightly used Tung Sol vt99’s (~$150-250pr.. not the fabled 6SN7gt/vt231 round plate, which are highly overrated for asking prices today). Tung Sol Vt99s, esp in this preamp are quieter, more revealing and more dynamic than their 6sn7gt variant which for some ungodly reason are getting $500+pr on eBay. I have both as well as many others. On the VT99, round plate, flat plate.. doesn’t matter. Both sound good. Another decent vt99/6f8g option are the Sylvanias sold by Buenos Aries Radio on eBay, but not quite as good as the TS VT99’s. 85-90% as good.
Disclaimer: I haven’t yet listened to the stock shuguang 6sn7gt’s that come with this preamp, but my general impression is that while most non-adapted smaller bottle 6sn7gts are ’safer’ (in terms of microphonics), they can’t approach the level of transparency and dynamics of a good adapted 6f8g/vt99 such as the Tung Sol or B/A Radio Sylvannias.
Disclaimer: I haven’t yet listened to the stock shuguang 6sn7gt’s that come with this preamp, but my general impression is that while most non-adapted smaller bottle 6sn7gts are ’safer’ (in terms of microphonics), they can’t approach the level of transparency and dynamics of a good adapted 6f8g/vt99 such as the Tung Sol or B/A Radio Sylvannias.
