Questions from a Tube Preamp newbie

I wouldn't use the term sparkle to describe the Brimars, I would say they have a nice amount of "air" in the highs, a very realistic sound.
RCA Cleartops and Amperex have sparkle, meaning extended highs. Never tried JJs.

My zus have the super tweeters and I do not want to add more sparkle. Now “air” should be fine. I may try a set. I guess if i thought they were a smidge too bright, i could always just use two and use two jjs

Yes, using a different tube type as cathode follower gives you an almost endless variation of sonics. Rogue responds very well to tube rolling and  there are many different 12AU7's.

Hi , I have a Rogue RP-1, not as nice  , but some similarities. I replaced the JJ’s after about 10 hours . I use medical grade NOS Telefunkens . I have 3 sets. I started with NOS RCA 12AU7WA tripple mica’s. Nice sound . I have NOS Mullards ECC 82’s , sounds like somebody threw a blanket over my system . Kinda like pushing the Dolby button on a cassette player . I also have 2 pairs of Seimens nickel plates and Amperex Holland . For my taste and in my system the Telefunkens are hands down my favorites . The Seimens are second , very linear and defined , but a little bright on the top . The Amperex are even brighter . Unless I change speakers , I’ll stay with the Telefunkens . I just took a pair out with about 5000 hrs . The Tectronix labels had changed color from the heat . Popped in a new pair and could tell a difference . I feel about 100 hours on the tubes have them settled in . Also I like NOS Tungsram and the E I crossed swords too . So for me , I spend on good NOS Telefunkens and for budget Tungsram . Although the Seimens are pretty sweet . I assume you have a quality power cord ? I also have had good results with Morrow MA5 interconnects, after 600 hrs . As far as Rogue, they tell most people to run Mullards . They even suggested them to my buddy for his 180 mono blocs . I’ve had Hiss Problems too . I just had hiss on one side , so I changed Tubes . I didn’t bother to see if just needed reseating, I just replaced them . Also with four Tubes , if one is gain and one is phase ( ask them ) changing just one tube per side will have a big influence . The JJ’s are cheap and reliable , perfect for mass sales . So happy listening and I’ve babbled enough . Regards , Mike. 

Hi Abery,

1. It really depends upon the preamp and the quality of the tubes.

2. NOT that I have noted, but I am no expert.

3. A tremendous difference. I'd seriously look for some Telefunkens. I can't be sure about the 12AU7's, but I think Telefunken's pretty much own the 12A-whatever family. 6DG8's I tend to prefer Bugle Boys for warmth and Siemens for detail, YMMV.

4. JJ's are likely pretty good for the mostly crappy tubes made today. While most things, like cars, televisions, etc. have improved, I suppose due to low demand tubes have gotten worse, much worse in some cases than the really good older tubes. Mind you, I said really good older tubes, many brands were no better than what you can buy new today.

Hope this helps.

@lous One current tube brand you may want to consider are Genalex Gold Lions sourced from Cryoset. I have yet to find any 12AU7s that work as well in my line stage as the GL’s. besides the fact that they have a neutral, dynamic, open sound, they last a l o n g time!