The focus of this page will be on IASCA and USAC competitors, and how to move from typical consumer products to custom made and application specific units.
Who’s on first??
Richard Clark’s famous Buick Regal Grand National was long considered the benchmark for Autosound competition vehicles. Hand made compression horns, custom transducer feedback circuitry, power supply stiffening capacitors, balanced signal transmission and lots of 120V Pro Sound gear. Apogee D/A converter, Rane equalizer and crossover all were modified to be use in the 12V Autosound environment.
Before you go out and purchase an Alesis, Yamaha, Behringer or Rane pro sound component, make sure you check your competition rule book. In IASCA, the unit must be powered by, and operating on 12V. The use of a 120V power inverter is prohibited. You will have to remove the existing power supply, and build your own. This can be a daunting task, so plan carefully.
The most commonly modified unit for Autosound use is an equalizer. As I mentioned; Alesis, Behringer, Yamaha and Rane are seen all over the competition circuit. Companies such as Image Dynamics and USD offer some of these units already converted for 12V use. This should be a serious consideration, since you will have a warranty.
Why use a pro sound unit?? Some people argue that there is no acoustical benefit from these practices, and that the benefit Is psycho-acoustic, that is, we think it sounds better only because we subconsciously believe it sounds better. This is a useful trick/tactic in competition, and can sway a judges perceptions greatly, if executed properly. In fact, the pro sound equipment, provided you choose wisely, may indeed offer excellent sonic performance, but is more likely to have features which you just can’t get anywhere else. Digitally stored equalization curves with around 100 presets, time alignment settings, crossover and filter adjustments and general level settings, all are stored and can be retrieved at the touch of a button. While car audio manufacturers are now on the bandwagon, the pro sound market has had these units in production for longer and in larger quantities.
Also, check that the unit you are looking at is truly digital, if that is what it claims to be. The Rockford Symmetry, while digitally controlled, still performs its filtering and equalization in an analog state. The Behringer UltraCurve 8000 on the other hand has a pair of Motorola DSP processors for sonic adjustments to amplitude and phase.
Another area where Autosound manufacturers are starting to focus is with high-end external D/A converters. Alpine (for a while now), Precision Power and Zapco all offer external units, using some of the industries best 1-bit and 20-bit converters. Burr-Brown is likely the most well recognized name in D/A technology.
The purpose of the D/A converter is to do just that, take the digital information from the CD, and faithfully and accurately transform it into an analog waveform which we then amplify as music. The more pure and accurate this conversion process is, the more realistic our music will sound, given that everything else is in the system is up to par.
Utilization of an External D/A is not always easy though. The fact that the signal must still pass through some sort of volume control make it difficult to design into a system, and it can be somewhat awkward to find a digital signal, from the average head unit, to feed to the converter. You may want to deal with someone who has done this is the past.
As far as using pro sound D/A converters, I have seen Audio Alchemy and Apogee units used in several occasions, so it most certainly can be accomplished, provided your wallet can handle it.