Car CD Changers
There are two methods of connecting a CD changer, either through direct connection to the head unit’s preamp or by FM modulation. Direct connection is done by a special cable that connects between the head unit and a compatible CD changer. This gives the CD changer power and control commands that allow it to work with the rest of the audio system. If an aftermarket CD changer is being direct connected to an OEM head unit, a special adapter will be needed to interface the two devices. Keep in mind that not just any CD changer will work with any CD changer control enabled OEM head units. The aftermarket changer must be made by the same manufacturer that makes the original factory OEM changer. Contact a specialty manufacturer such as Precision Interface Electronics (PIE) or Blitzsafe that manufacture these adapters.
The second method is through an FM modulator and is probably the most common way of connecting a CD changer to an OEM head unit or aftermarket head unit that lacks CD changer controls. In this method the CD changer interfaces with an outboard control unit that accepts the music signal from the changer and converts it to an FM radio signal. This FM radio signal then passes to the FM tuner section of the head unit through the radio antenna plug. The modulator unit receives signals from a wired remote control that is usually placed on the dash or console within easy reach of the driver. This remote controls track, seek, disc, and other functions and displays the CD information on its screen. The drawbacks to this method over the direct connect method are two fold. First, the addition of a second control unit can be confusing and looks less clean then a one control unit setup. Second, the sound quality will not be as good as with a direct connection. The reason for this has to do with how the signal is passed to the head unit. In a direct connection the music passes as a clean preamp signal that is then amplified by the head unit. With an FM modulator the sound quality is limited by the frequency response of your FM radio section. While a direct connection will pass the entire audio band from 20Hz-20kHz, the FM tuner will only cover the spectrum of the FM band which will lower the high frequency response otherwise possible with a CD system. An FM modulated system will sound like a radio station with excellent reception. Certainly acceptable sound but not true audiophile quality and something to be aware of.
Features to look for when shopping for a CD changer are:
CDR/CDRW Comptability: While most CD changers can read CD recordable discs, not all can read CD Re-Writable discs. This may be important if you burn your own CDs.
Disc Capacity: The number of CDs that the CD changer can hold. This will range from 6 to 12, though 50 disc changers are available. The more your CD changer can hold, the less often you will have to change the discs.
Disc Changing Time: The time it takes a CD changer to go from CD to CD. Though it has no effect on sound quality, if you are impatient you might want to take this into account.
Frequency Response: This is the portion of the audio spectrum a piece of equipment can produce. The average human can hear sounds in the range of 20Hz-20kHz. Most good CD changers can produce this entire range.
Loading Method: The means by which CDs are loaded into the CD changer. The most common is by a removable CD magazine. Some in-dash CD changers units accept CDs directly.
MP3 capability: Many newer changes have the ability to play MP3 encoded discs. This can be a real benefit if you have a CD burner and a collection of MP3s on your computer as it eliminates the need to have additional equipment to play your MP3 collection in your automobile.
Skip Protection: Some CD changers have a built in memory buffer, usually between three and ten seconds, that will continue to play the music skip free even when the player is actually mis-tracking. This is a great feature if you drive on a lot of bumpy roads but is an uncommon feature usually reserved for higher end changers and MD units.
Size: This is the physical size of the CD changer itself. It's important to know if you have limited space in your chosen mounting location. Some units are even small enough to fit in the dash or glove compartment.
The Car Audio Help DVD catalog includes five different videos covering many areas of car audio installation and custom fabrication. Topics range from basic system installation (head units, CD changers, amps, speakers, etc.) and mobile security (car alarms and remote start) to subwoofer box design and fiberglass fabrication. If you're interested in custom fabrication and car audio installation be sure to check out what we have to offer.
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