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
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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....
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Oldpet,
I like my Supratek very much. It is a very musical preamp. I was lucky because a friend had a nearly new Chenin(less than two months old) that I was able to buy immediately when I found out that the H-Cat wasn't my cup of tea. I must say that another preamp on my short list was the First Sound. Best of luck on your audio adventures. Bob