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Why do we have faders? Why don't we just have knobs?

There is nothing so iconic about sound engineering than faders. Like the keys of a piano, the faders of the mixing console are the gateway to the wonderful sounds within.


When recording was first invented, musicians would cluster around the microphone (actually a mechanical horn). Lead instruments and quiet instruments were closer, loud instruments and background instruments were further away.

It was a primitive form of mixing, and it worked to an extent. But as soon as electronic recording became possible it was realized that the outputs of several microphones could be combined electronically.

And to do that the mixing consoles of the day had...


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Yes, rotary level controls. Generally quite large ones that you could really get your hands around. But you have to wonder why knobs then, and why faders now?

Linear controllers were also available during the early days of sound engineering. I have seen examples that were used as lighting dimmers. Rheostats they were called, and they were really big. And then some bright spark had the idea of curling them round into a circle to save space.

The whole thing was then scaled down since audio doesn't use anywhere near as much voltage and current as lighting. In audio, we call the rheostat a potentiometer. And since the potentiometers that controlled the levels were circular, it made absolute sense to control them with circular knobs.

So what's the problem with knobs?

Simple, controlling level is the most important aspect of mixing. There is nothing else that even comes close. And in mixing that is done live, for radio or TV broadcast for instance, the engineer needs to know where the levels are at all times.

But you can't see that easily with a knob. Yes, the knob has an indicator line or pointer, but you have to look closely. Every half-second taken adds up. And of course there are several or perhaps many knobs to handle.

Another problem with the knob is that it is almost impossible to turn two at the same rate. And you can't even attempt to turn more than two at the same time.

So a solution was sought. And it was to...

Turn the whole thing around by 90 degrees so that the resistive track of the potentiometer was vertical. It was controlled by what we would now call a 'quadrant fader'. It's like a modern fader, but it moves around the arc of a circle rather than on a flat surface.

Now, not only could the engineer see at a glance where ALL the levels were, he could move two faders at the same time, at the same rate. And in fact move several faders at the same time.

I don't know exactly when or why this first evolved into the linear fader, but I imagine that it seemed like a neater solution. And it is, although if quadrant faders had stuck around they would have developed further, I have no doubt.

But the quadrant fader has one advantage that the linear fader does not - you can tell where it is purely by feel.

This is very important for the TV or film sound mixer. Also when mixing music it is better to keep one's head level because the frequency response of the ear changes when the head is tilted.

I'm not suggesting a return to quadrant faders as clearly they have had their day. But one has to wonder whether the modern fader is the ultimate in design yet.

If you look at early keyboard instruments such as harpsichords, clavichords and organs, you will see that the keys are all different shapes and sizes from one instrument to another. The same basic layout, but no standardization.

The keys of all keyboard instruments, except some intended as toys, are the same size now. And they fit the hand so well that you can't imagine that any improvement would be possible.

We haven't quite reached such a degree of standardization in faders yet. Before that happens, maybe it would be worth a little thought and experimentation to see if a better design is possible.

Don't tell me your ideas though - get down to the patent office first. If you can come up with something to replace the fader then you will soon be worth millions!

By David Mellor Thursday November 30, 2006