Audio Horizons TP 2.0 Preamplifier

I am getting the 2.1nR should be here Friday.
I see were people are changing out tubes 1 and 3. Can I ask why those two??
I have a pretty good stash of NOS tubes I am going to be trying but am curious as to why different tubes in 1&3 and 2&4?? what do these tube locations do.
Thanks for any help

Gammajo
Thanks for the info, as for tubes I have quads of Amperex pinched waist, PQ D getter,cca's, Mullards and numerous other's.
I use four in my amps and have been stashing tubes away for years should be kind of fun tube rolling as I haven't done that alone for a couple years.
I will try all but was a bit confused on the different tubes being used in the different positions.
Thanks again for your response.

Also how is the AH power cord on the pre?

Is there any involvement from MR. Hall of Electraglide in these cords?? The design looks allot like his cords.I know Audiofankj was selling Electraglide cords and know Electraglide used to be in Alpharetta Ga and Audio Surroundings which is selling the new power cords is also in Alpharetta, GA ?

Have you tried these on other components I am looking for a new cord myself,I use two Epiphany X's in my system now.

Thanks

Kirk at Fusion Audio is that Audiofankj??
Thanks

Sherod
Why is your main system down??