Evolution of the Dj Mixer Crossfader

RaneNote EVOLUTION OF THE DJ MIXER CROSSFADER Evolution of the DJ Mixer Origination Crossfader The DJ mixer crossfader was originally developed as a control for implementing smooth fades from one pro- • History gram source to another, but where did the idea come from? Fading between two independent sources was • Curves first accomplished by DJs using two rotary knobs. They would maintain constant acoustic energy (equal loud- • Pots - VCAs - Magnetics ness) in the room while carefully fading from one program source to another. Some expertise was required • Performance to accomplish this effect accurately and consistently. It became obvious that if a way could be found to fade from one source to another with a single control, the task would be much easier and repeatable for the less experienced. Rick Jeffs Rane Corporation RaneNote 146 © 1999 Rane Corporation A condensed version ran in DJ Times, June 1999 Crossfader-1 Panning circuits were already used in recording where the term “fader” has been in use since at least studios to move a single source from left-to-right while the ’50s (mentioned throughout the Radiotron De- maintaining constant acoustic energy. While the signer’s Handbook, 4th ed., 1952) and the term “cross- requirements for a single source panning circuit were fading” shows up in the Tremaine’s Audio Cyclopedia well defined, those for maintaining constant acoustic in 1973. The earliest example documented so far was energy while fading from one source to another were designed by Richard Wadman, one of the founders of not. the British company Citronic. It was called the model The exact origin of the first use of a crossfader in the SMP101, made about 1977, and had a crossfader that DJ world has proven difficult to track down. It seems doubled as a L/R balance control or a crossfade be- certain to have come out of the broadcast industry, tween two inputs. "Rosie" is the first known DJ mixer, circa 1965. Courtesy EMP (Experience Music Project, Seattle). Crossfader-2 1st Generation Curve Shape 2nd Generation Curve Slope Knowledgeable engineers noted that if two source sig- It was soon clear that one crossfader response curve nals of equal rms amplitude were statistically random was not suitable for all applications. No matter how and incoherent, a slight modification to the standard skilled the DJ, it was not possible to achieve all of the panning circuit would allow constant energy fading desired effects. At first, the applications were distinct between sources. The new control was called a cross- enough that manufacturers could design special mix- fader and has achieved wide use and acceptance. Figure ers by selecting one of the tapers shown in Figures 1-4 1 shows the classic constant-power response. for specific applications. However, as DJ performances The curve shown in Figure 1 only yields constant- became more sophisticated and competitive, a fixed power fading when the original source signal assump- taper became inadequate. DJs wanted to mix it up. By tions are true. now they were familiar with the results possible with Limitations: It wasn’t long before the basic cross- the various tapers and wanted them all. For performing fader topology showed some limitations. Disco dance DJs, the days of the application specific crossfader were music with a dominant beat challenged the original over. assumption of random. As beat matching source rd signals gained popularity, the assumption of incoher- 3 Generation Curve Slope ence became invalid. Those who had mastered the skill The solution was to provide a second control that of two-knob-fading scoffed at the idea of a crossfader would allow the DJ to change the crossfader taper. control, and were now saying “we told you so.” It was Limitations: At this point, most designers had lost apparent the traditional crossfader lacked flexibility. track of the original constant-power crossfader taper. In addition to the fundamental, smooth crossfade re- Implementations had become careless and undefined. sponse shown in Figure 1, DJs wanted to perform more Defined standards did not exist for the tapers shown in complex mixing functions. They wanted to add one Figures 2-4. When crossfader taper control was added, dance song to another without losing energy in either it was not surprising that the range and shape of tapers until fully mixed. They wanted to cut in a beat and then was haphazard. Each implementation performed differ- pump it up. They wanted to cut one program in and out ently, causing confusion among performers. without affecting the other. Figures 2-4 show some of The best passive controls could not meet the increas- the tapers required for various effects. ing demands on performance and usage. Passive controls are rated for a maximum number of operations, while maintaining given travel noise and force specifi- cations. As the number of operations increases, travel noise goes up and travel force changes. Even high-quality controls with cycle life ratings as high as 100,000 to 300,000 require frequent service or replacement. CROSSFADER RESPONSE CROSSFADER RESPONSE 5 0 5 0 4 -10 4 -10 SUM 3 -20 3 -20 BUS B BUS A BUS A BUS B 2 -30 2 -30 1 -40 1 -40 SUM 0 -50 0 -50 SUM (dB) -1 -60 SUM (dB) -1 -60 -2 -70 -2 -70 A/B AMPLITUDE (dB) -3 -80 -3 -80 A/B AMPLITUDE (dB) -4 -90 -4 -90 -5 -100 -5 -100 0102030405060708090 100 0102030405060708090 100 % TRAVEL % TRAVEL BUS A BUS B SUM BUS A BUS B SUM Figure 2. “No Dip” Taper for Adding Sources Figure 1. Constant-Power Response Crossfader-3 4th Generation Curve Slope The Musical Instrument Connection The high maintenance requirements of passive cross- A new art form emerged from hip-hop. Turntablist faders resulted in unacceptable service costs and down (scratch DJs) take small bits and pieces of music from time. It was bothersome to disassemble a mixer just to different locations on vinyl records and create new clean and lubricate the controls. Replacement required compositions. A mixer and a couple of turntables costly factory service and could leave a DJ without in- become their instrument. This emerging art form again come for weeks. The solution was to design mixers with put demands on crossfaders that current state-of-the- field-serviceable crossfaders. While doing nothing to art designs could not meet. resolve the reliability problems, the removable cross- The following is a list of the new requirements: fader did help reduce service costs and down time. • Music instrument quality and performance. • Accuracy, reliability and repeatability for all th 5 Generation Curve Slope functions. To improve performance and extend service life, audio • More than a 10-times increase in crossfader usage was removed from the crossfader control and pro- over previous applications. cessed in a voltage-controlled amplifier (VCA) or some • Crossfader with a taper range adjustable from other voltage/current controlled element. The crossfad- constant-power to less than a .1 inch (2.5mm) pitch er control was only used to develop a DC control sig- between full off and maximum level. nal. However, this implementation was found only on • Mechanically durable crossfader control with a knob expensive mixers. This practice greatly reduced travel that provided a fine music instrument feel. noise and extended service life, but the performance • Crossfader taper control with smooth & predictable of affordable VCAs was limited. In addition, crossfader settings. tapers were still poorly defined as were the controls • Reverse operation of the crossfader. used to alter the tapers. Implementations were complex In addition to the new crossfader demands, all of the and consistency was poor. same demands were now placed on the input (or pro- Rane developed an Active Crossfader™ design, featur- gram) faders. ing high quality VCAs, low cost, and simplicity. The None of the existing designs met all of the new classic response of the design is shown in Figure 1. demands. In addition, many manufacturers were timid In addition to providing an accurate constant-power about providing any product for fear of service liability response, the circuit produced the optimum integra- problems. Available products were either very expen- tion time for removing travel noise without noticeably sive with limited performance and feature-sets, or affecting the reaction time of the control. The Active cheap throw-away toys with virtually no warranty. Crossfader topology created an excellent foundation for more sophisticated designs. CROSSFADER RESPONSE CROSSFADER RESPONSE 5 0 5 0 BUS B BUS A 4 -10 4 -10 BUS B SUM BUS A SUM 3 -20 3 -20 2 -30 2 -30 1 -40 1 -40 0 -50 0 -50 SUM (dB) -1 -60 SUM (dB) -1 -60 -2 -70 -2 -70 A/B AMPLITUDE (dB) -3 -80 -3 -80 A/B AMPLITUDE (dB) -4 -90 -4 -90 -5 -100 -5 -100 0102030405060708090 100 0102030405060708090 100 % TRAVEL % TRAVEL BUS A BUS B SUM BUS A BUS B SUM Figure 3. Medium Taper for Cut In and Pump-It-Up Figure 4. Sharp Taper for Cut and Scratch Crossfader-4 Rane accepted the challenge and designed a perfor- Magnetics mance mixer meeting all of the new demands, with The new patented Rane magnetic fader is the fastest, music instrument quality and reliability. Because the most accurate, and longest lasting on the planet. The combination of features was complex, and performance design uses non-contact technology previously re- requirements very high, it was apparent that the new served for the most demanding aerospace and indus- design would need new technology. trial applications. No travel noise — no bleed — ever. The challenge was to find an active or VCA topology Unlike optical non-contact faders, Rane’s magnetic that would provide the required performance without fader is impervious to smoke, moisture, temperature, excessive cost or complexity.

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