tube upgrade for first sound


Has anyone been able to improve on the stock tubes in the First Sound preamps? I was thinking about trying the Russian 6H23. Any thoughts? thanks
84audio
Two updates:

FIM Model 88 Outlet. Emmanuel recommended it over the more expensive wattgate I had, and he nailed it. This thin gis a must-have for this preamp. Quiet as I'll get out, smooth as silk, yest highly resolving/transparent. This one doesn't rob dunamicsd or over-smooth things - it's very neutral. At $60, you can NOT go wrong. Trust me, this was pretty impressive, not subtle....

next up: early 1960's US-made pinched waist Amperex 6922's. I returend the "Siemens 7308 gold pins" when i discovered (while trying to resell them here) that they were manufactured in 1980. Yeouch! they really didnt hold a candle to the Amperex D-getter 6922's or Phillips Miniwatt 1959/1960 (aka Bugle Boy)tubes I had on hand, no matter how much I tried to like their "transparent" sound - they sucked - and now I know why. Boys and Girls: it's a jungle out there. make sure you know a priori what year your tubes were made before you buy....

On that note, Andy at Vintage Tube Services is 100% bone fide honest and waaaay more knowledgable than most out there.
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Artg

My system is pretty simple. you know - simple is as simple does - :-) I currently have a McCormack UDP1 - very outstanding on redbook /SACD/ DVDA. DVD-V is fun too. Although I'm not THAT much of a videophile. The UDP1 runs into a Lexicon MC8 - great for HT. Not really too bad for 2 chanel either. My amp is the Krell FPB 400cx - what can i say - outstanding, to me anyway.
Speakers are Tyler Accoustic Linbrook Signature system. (single piece speaker) - These, I love more and more all the time! :-)
BUT I've always wanted to try tubes. Since I do mostly 2 channel listening I thought a dedicated 2 channel tubed pre would be a good idea.
So, I started checking into the in's and out's of tube pre's. I ran into the whole DC leakage thing as it relates to Krell amps - not good. Then started to hear of preamps which did not leak DC, by design. So I tried 2 different tube preamps along the way, but they didn't do all i wanted. Then i began to learn about the 'real deal' preamps - I read the soundstage review of the First Sound presence Deluxe II - (advice from Tvad) and here i am.

I hope that the FS does what i want. From the reviews i've read. i'm pretty sure it will. As I type this little synopsis of my 'rig' :-) I realize that there are ALOT of good folks who offer sound advice, and encouraging words here on Agon. I say Thank YOU to to each and every one. (you know who you are) :-)

thanks for everything
BTW just got some Amperex 6922 USN white lable's for after breakin - what do you think?

Paul