Faders

The crossfader is the component of the DJ mixer that is most important to turntablists.

Intro

Early DJ crossfaders were a simple carbon-track design, and contained two pairs of Logarithmic curves. This made the crossfader essentially equivalent to two back-to-back input faders. These were adequate for looping and beat-juggling, but made performing even basic scratches very difficult. In addition, the faders simply weren't designed to withstand the number of cycles a typical turntablist would put them through in a day, let alone a few years. As a result, many/most early scratch DJs used the phono/line selector switch to cut instead.

By the early 90s, performance mixers (such as the mx-2200) had faders with sharper curves, and used a carbon/plastic hybrid design to increase the durability. Still later mixers, such as the Vestax PMC Pro series, switched the passive fader design for VCA circuits. These allowed advanced features like control voltage filtering (increasing fader life even further) and curve adjustment.

The current generation of performance mixers have a wide variety of novel non-contact methods of sensing fader position.

Fader requirements

Turntablists have the following requirements in a crossfader :

• Low friction - the wiper should move with as little friction as possible.
• High durability - the fader should be able to withstand significant lateral and forward-backward force at all wiper positions.
• Long operational lifecycle - the faders lifecycle should be specified in the millions of operations, ideally tens of millions.

Other factors to consider include :

• Wiper weight - The inertia of a fader depends on its mass. For example, the Focus Fader is extremely light and thus has very little inertia, whereas the large metal stem base used in Vestax PCV faders gives them a much larger inertia.
• Rebound damping - different faders have different means of damping the wiper when it hits the interior wall of the enclosure. The ALPS faders used in early Vestax PMC Pro mixers have no damping whatsoever, whereas Pioneer's Magvel fader used in its most recent performance mixers have a full range of interchangeable rubber stoppers with different rebound characteristics.
• Dead zones - faders often have dead zones or "lag" at each end of the wiper travel, where the movement of the wiper has no effect. Large dead zones affect the ability of the mixer circuit to reduce the cut-in distance.

Design approaches

Mechanical characteristics

Generally speaking there are two types of fader mechanical designs :

Spring suspension

Wipers in spring suspension faders are suspended between two metal springs - an upper spring that pushes upwards against the top of the metal enclosure, and the lower metal brush that actually makes electrical contact with the fader's carbon tracks.

These faders are cheap as they contain very few parts, and can be made very small. However, they are not very durable due to there being no strong wiper support structure and generally have a short lifespan due to the brush contacts being an integral part of the support mechanism. In addition, they are usually lubricated with a fairly viscous lubricant so are not ideal for turntablists.

Perhaps most DJ faders are of this type, including (until recently) premium mixers such as the Pioneer DJM series, however they are not generally found in performance mixers for the above reason.

Railed

The wiper slides along one or more polished steel rails, which allows for greatly improved durability and lifespan as the mechanical support is separated from the electrical mechanism. This also allows for position sensing methods other than the traditional metal brush/carbon track combination.

Most of the faders found in performance mixers are of this type, but can be separated into two categories :

• Short bodied - these have the rails placed horizontally side-by-side. This allows the fader enclosure to be of a similar size to spring suspension designs, but they do not have great angular stability in the wiper as there is no vertical distance between the rails. The only commercial turntablist-suitable fader with this design is the Mini Innofader, but some enthusiasts are building miniature variations of the Focus Fader.

• Long bodied - these have the rails places vertically, one above the other. This design keeps the wiper very stable, but require a lot more space inside the mixer to accommodate the taller fader enclosure. Many turntablist-oriented faders have been released in this format :
  • Vestax PCV and its CF-CC variant
  • Eclectic Breaks Pro X Fade
  • Audioinnovate Innofader
  • Ecler Eternal Fader

Electronic characteristics

Discussion of the circuit requirements Mixer circuit