I would say that a good architect, and a good development process, certainly involve collaboration between numerous stakeholders. The solution architect, tech leads, product owners, QA, etc., all have a voice and should all be talking to each other quite a lot.
That said, it's good to have somebody who owns the overall vision of the technical architecture, and can be a tie-breaking vote, or exercise veto authority over things when needed.
All in all, I believe the main job of the solution architect is to define, and defend, the "skeleton" of the solution, and then let everybody else hang their respective pieces off of that skeleton. Done right, the skeleton should be just prescriptive enough that any "component" attached to it will work smoothly with the others.
That said, it's good to have somebody who owns the overall vision of the technical architecture, and can be a tie-breaking vote, or exercise veto authority over things when needed.
All in all, I believe the main job of the solution architect is to define, and defend, the "skeleton" of the solution, and then let everybody else hang their respective pieces off of that skeleton. Done right, the skeleton should be just prescriptive enough that any "component" attached to it will work smoothly with the others.