The Premier 17LS uses 4 6DJ8 family tubes. This means 4 of the same type of 6DJ8, 6922, or 7308. The type, brand, and variation of the tubes will definitely have an effect. Out of the box the 17LS came with Sovtek 6922s - these are decent tubes though they tend to be a wee bit mechanical/analytical sounding and their top end is not as sweet or extended as others. The Sovteks might yield a slightly forward soundstage, but not to the extent of moving the soundstage to the extent you describe.
My experience with the 17LS found it having a somewhat recessed soundstage - as if you moved farther back in the hall. This was in conjunction with a pair of CJ Premier 12 amps. Not recessed versus in front of the speakers, but simply further behind the speakers. I found the original Shunyata Hydra had a profound positive effect on the 17LS - much more so than on say a 16LS - it opened up the soundstage in terms of width and depth, gave a better sense of air around musicians, and brought the soudnstage forward some, so you didn't feel like you were in the balcony.
Cheers,
Tim
My experience with the 17LS found it having a somewhat recessed soundstage - as if you moved farther back in the hall. This was in conjunction with a pair of CJ Premier 12 amps. Not recessed versus in front of the speakers, but simply further behind the speakers. I found the original Shunyata Hydra had a profound positive effect on the 17LS - much more so than on say a 16LS - it opened up the soundstage in terms of width and depth, gave a better sense of air around musicians, and brought the soudnstage forward some, so you didn't feel like you were in the balcony.
Cheers,
Tim