After getting good results from the 3 used JJ brand tubes that I borrowed from my friend, I decided to order 5 new JJ tubes from thetubestore.com.
New tubes arrived today and tested them few hours ago at home practise volume levels.
I read in internet that in these preamps, the V1 and V4 affects the sound most therefore I ordered 2 of them to be "Gold Pin" models which JJ claims that they are the selected premium grade tubes in their production line.
So the final configuration is:
V1) JJ ECC83-S / 12AX7 (Gold Pin)
V2) JJ ECC83-S / 12AX7
V3) JJ ECC83-S / 12AX7
V4) JJ ECC802-S / 12AU7 (Gold Pin)
V5) JJ ECC83-S / 12AX7
I can definitely say that the result is better than ever. Tone improved a huge amount. It is smoother, warmer and punchier. High-mids are "singing" as good as ever and also the 60Hz hum is almost gone completely and the hissing noise reduced a huge amount.
In the end I can highly recommend using new JJ brand tubes in this preamp.
Next step for me is to try NOS tubes if I can find them in the future. The preamp's sound is quite good now and can't imagine how reasonably better tubes can improve the tone but perhaps the difference will be like smoking a usual tobacco in a bad pipe versus smoking a well aged tobacco in a good pipe. We will see
Altough I have been using an all-tube head for 20 years at home. I have never experimented or bothered with different tubes before since it's hard to find vacuum tubes where I live. So my experience about the sound of different tubes are very limited however I can understand or feel the sound of a good tube sound.
I will be playing today with my band at our usual tuesday night classical rock bar gig and the new tubes will also be used first time on stage at loud volume. Can't wait
I will keep experimenting and hopefully will inform you all again.