My brother is an excellent singer/song writer/guitar player and he's looking to get protools to record on the computer. I asked why he NEEDS protools and he can't just use a quarter inch to eighth inch converter and plug his guitar into the computer, and he said that the hardware does something with the signal that would otherwise be lost. Is there anything to this, or is it $40 of scrap metal?
The quality of audio-digital hardware you use does make a lot of difference to the quality of any recording you will make through it.
Good ones will have wider frequency response, less susceptibility to interference and mains hum, and will have low latency. These are essential if you want to make a recording sound its best.
The main benefit of Protools (consumer level systems) is the software, not the hardware.
Digidesign requires the presence of one of their hardware interfaces attached to the computer for their software to launch.
No Digidesign hardware, no ProTools software.
Their hardware is great too, but the main benefit is the ProTools software since that is the ubiquitous software in the recording world.
But yes, especially in the higher end systems the ProTools hardware is very highly engineered and dedicated to recording extremely high quality audio.