You have to admit, the linear fader is a brilliant invention. You can control levels easily, judge how much you are changing the level just by feel, change multiple channels by the same amount, and get a visual indication of relative levels. That's a powerful package, and a good reason why we still use a visual representation of physical faders in software recording systems.
So what did recording engineers use before faders were invented? Well in the earliest days there were rotary controls, like you find elsewhere on the mixing console and on outboard equipment. And even before that there were rotary controls that were actually multi-position switches – they did not operate continuously like potentiometers.
But the disadvantage of rotary controls is that you have to look at the indicator to see what position they are in. And you can't do any of the things listed among the advantages of faders.
The next stage of development of level control was a kind of halfway house – a rotary control, but with its axis shifted 90 degrees. This gives us the quadrant fader.
Now if you are into retro gear, then doubtless you will find the look of the quadrant fader very appealing. But there is more to it than that…
Quadrant faders actually have one significant advantage over linear faders. Now what could that be…?
OK, here's a test. Sit in front of your mixing console and close your eyes. Reach out for a fader. Now tell me what position it is in. 0 dB? +10 dB? -30 dB?
You don't know, do you?
But with a quadrant fader, you can actually feel the position it is in without having to look. With mixing being such an aural experience, anything that releases the brain from high-intensity visual tasks just has to be good.
Maybe that's why some of those old recordings sound so great.
Now, if only someone could work out how to emulate a quadrant fader in software…