I spoke with ARC and they said that the position does not matter, as each tube actually is a "stereo" tube so inside each tube will flow the signal of both channels.
They confirmed what Hansk46 said above: if I use two pairs of tubes put them in V1+V2 and V3+V4.
Thanks to all.
They confirmed what Hansk46 said above: if I use two pairs of tubes put them in V1+V2 and V3+V4.
Thanks to all.