How Do Amps Affect Soundstage?

The more info I have the better thanks

Amplifiers matter because of noise, white noise accumulated through signal conditioning and amplification stages. Dead quiet to loud matters. Tubes, like jfets, and mosfets do not have a lot of current input and therefore have almost zero current noise. Voltage noise can be mitigated relatively easily. The listening  experience that enlightened me is from a Counterpoint Solid 2, blown up, that I fixed and changed minutely to drive, any speaker or simply weld to music. I was completely blown away after getting it going.. I wanted to listen to this thing, testing forever with my elac 6.2 debut monitors. My friend Dave, the amps owner was blown away too. Preamps because of noise, and of course speakers the biggest deal.      

Nelson Pass uses a technique of adding an out of phase 2nd harmonic distortion to his designs. This will give you more spatial information and the feeling that the notes are in the air. 

If we think about it in it’s simplist terms, a deep, wide soundstage requires a stereo signal. The more "mono" the signal is, the more it will "move to the center" narrowing the soundstage assuming the channels are in phase.  If the channel interactions are out of phase, the soundstage gets more "nebulous" as separation is lost.

So, it would seem that an amp that has poor channel separation would not produce as nice and wide a soundstage as an amp that has better separation. And of course, anything (e.g., interchannel distortion) that affects both channels similarly is also in mono so hurts the soundstage presentation.

The pairing of the amp with the speakers matter more generally than the amp itself...For soundstage... ( for bad amp exist too )

But the main central factor is the pairing speakers/room if by soundstage we means not only differential imaging and the soundstaging measured apparent dimensions but also 3-D holographic volume for each instruments...

Also on par with the relation Speakers/room will be the recording itself... All recordings played on an audio system  did not give rise to a soundfield filling  all the room in front and behind the speakers and around the listener...Some recording lack lateral presence or in detph differentiation, some others put the sound more out of the speakers laterally and not in front of us too etc... i experienced all possible soundstage dimensions in my room... Thisc differ from recordings to recordings...

The choice of dac and the choice of the amp import less than the total synergy between them and with the speakers/ room acoustic... the  speakers/room acoustic pairing and coupling and the recording state of each album  being the two most impactful parameter after the synergy between amp and speakers  which is the less important factor but without it nothing will work well...

At the end not all factor impact the same but each one of them matter...Nothing impact so heavily than acoustic , but if the synergy between speakers and amp is not optimal, you will not be able to correct it with acoustic...