The Steel Guitar Forum

is there any difference between having one pickup than two pickups? is the any change in the sound quality ?

It depends...if you take a guitar like the Stringmaster and its clones, they are better thought of as a single pickup with two coils that may be blended. Having the two pickups blendable in series gives you some variation but I generally leave mine on full blast.

There are (slightly less common than the single pickup design) guitars with separate neck and bridge pickups...Asher has a lot of guitars like that. That's going to give you a broader range of tonal variation but just using the bridge pickup is most common in the stereotypical steel guitar genres (Hawaiian, country). I think the neck pickups may be intended more for people playing blues or roots music, with the bar staying closer to the nut in general, more open strings. But that's just my 2c/ conjecture...

There's a huge change in the sound, even if the pickups are placed close together.

There's increased output, differences in the magnetic pull on the strings, each pickup will have a different frequency response based on the position under the strings - strings vibrate in harmonic patterns and each pickup will be under a different part of the harmonics.

You really should Google the subject. It would take pages of typing to fully explain.