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
oldpet tell us more about your system. There are a bunch of highly satisfied FS oweners here - we want to know more about your rig.

Also, allow the thing to break in at east 3 weks before coming to any conclusions - AND REMEMBER IT INVERTS PHASE, so you need to account for that.
Yes, it inverts absolute phase. This is different than the out-of-phase
most of us are familiar with in which the imaging out of whack. I
pesonally can't hear the difference with a unit out of absolute phase and
in absolute phase, but I don't really know what to listen for either. Artg,
can you hear the difference?
I can't hear the difference either, and there's the POV that half of all recordings are inverted anyway. But I have my speakeer leads reversed at the amp just the same as Emmannuel Go is quite insistent about this.

And Paul, as many have mentioned, plug it straight into the wall. After a while, you will want to play with aftermarket power cords.
Id be lying if I said I could always hear the difference, but on some, the bass is off. On other recordings, i cant tell. Mostly i bring it to your attention because emmanuel really really feels strongly about it....
No question that FS owners should swap speaker leads according to Emmanuel's suggestion. There is no argument from me on that issue. I'm just really interested to know what to listen for regarding absolute phase. Alex Peychev has an absolute phase switch on his APL Denon3910 that is remote switchable, too. I've switched that thing back and forth a dozen or more times. Sometimes I think I hear a slightly more expansive soundstage. Other times I'm not sure. It's more of a brain teaser for me at this juncture.