Also, I'm good at listening to music, not eloquently commenting on it, so bear with me.
I find this combo of tubes and amp to be pretty neutral for a tube amp. It can reach real low and hit highs without being sibilant (as of my first listen). I'm looking to replace my Bushmaster MKII in favor of a DAC with more options. I'm really interested in the AudioGD line specifically the ESS9018 implementations, but fear that it may be a bit too cold from what I've read. Anyone care to throw in their two cents for a DAC that synergizes well with LF339?
The 5998 + 5693 are mostly used with this amp for it to power planars as they have more gain. No this combination does not sound very tube like, it's more of a neutral and slightly aggressive sound. If you want to hear the real 339 tube sound you should get some RCA 6AS7G and some 6SJ7GT mesh plates. Heaven.
I did not like my Audio GD NFB dac with the 339.
My Vio V800 does well with my 337 but that amp model's said to sound even more neutral / ss-like than the 339 and that suits me just fine. About DACs and tube amps: I don't know. I'm not a strict objectivist but I do believe that if a DAC is well built, any differences in reproduction will be insignificant when paired with a tube amplifier which is 'inherently' inaccurate vs a sand amp. It's the construction of the amplifier, more than the DAC or even the tubes, that will determine the sound.
Just my 2c of course.
BTW: your 5998/5693 combo is what I also use a lot with my 337, I find that the 5693 put some 'meat on the bones' of the music.
The Violectric V800 does good with anything ;-)