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MP3 Car Adapters - Music Magic

Playing Mp3 Music In Your Corvette

Tom Benford Dec 1, 2007

If you're the owner of a C6 Corvette, your factory stereo system has the ability to play MP3 files on CD. If you're a younger, or at least a technologically "hip" Corvette owner, then you're probably already up to speed on what MP3 is and what it's done to music distribution, portability, storage, and accessibility. If you're "old school" and don't know much or anything about MP3, this will serve to give you a brief introduction to it, and you may find, as millions of others have, that it's a great way to take a huge amount of music on the road, stored on a device that's small enough to fit in your shirt pocket. More importantly, you can enjoy all your favorite tunes stored in the MP3 format playing through the FM radio and stereo system in your Corvette with some very inexpensive, noninvasive plug-n-play devices we'll also be covering. But first things first.

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VRFM7 (MSRP $29.99)
* Transmits all your audio devices, including MP3 players, CD and DVD players through its audio input wirelessly to your Corvette's FM stereo system includes a built-in USB slot and MP3 decoder
* Dual function buttons: Play, Stop, Volume, and Track selection controls
* Plug-n-play your MP3s and WMAs, wire-free from your USB Flash Drive
* 7 LED preset indicators for FM frequencies (Low Band)
* 3-foot audio cable
* 2.5mm stereo input
* 12-volt wire-free transmission

Just What Is MP3?
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular digital audio encoding and lossy (you lose some audio quality) compression format invented and standardized in 1991 by a team of engineers directed by the Fraunhofer Society in Germany. It was designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners. In popular usage, MP3 also refers to files of sound or music recordings stored in the MP3 format on computers. A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is "close enough" to be useful in some way. This type of compression is used frequently on the Internet and, especially, in streaming media and telephony applications. These methods are typically referred to as CODECS (Compression/ DECompression) in this context.

In the first half of 1995 through the late '90s, MP3 files began flourishing on the Internet. MP3 popularity was mostly due to, and interchangeable with, the successes of companies and software packages like Nullsoft's Winamp (released in 1997), mpg123, and Napster (released in 1999). Those programs made it very easy for the average user to playback, create, share, and collect MP3s.

Quality Of Mp3 Audio
Because MP3 is a lossy format, it is able to provide a number of different options for its bit rate-the number of bits of encoded data that are used to represent each second of audio. Typically, the rates chosen are between 128 and 320 kilobits per second. By contrast, uncompressed audio as stored on a compact disc has a bit rate of 1411.2 kbit/s (16 bits/sample x 44100 samples/second x 2 channels).

MP3 files encoded with a lower bit rate will generally play back at a lower quality. With too low a bit rate, compression artifacts (i.e., sounds that were not present in the original recording) may appear in the reproduction. A good demonstration of compression artifacts is provided by the sound of applause-it is hard to compress because of its randomness and sharp attacks, therefore, the failings of the encoder are more obvious and are audible as ringing or pre-echo.

Corp_0712_02_z Music_magic Vrfm6 3/8

(MSRP $19.99)

* Transmits all your audio devices including MP3 players, CD and DVD players through its audio input wirelessly to your Corvette's FM stereo system
* Digital LED Display for 15 FM Frequencies (8 low and 7 high)
* 3-foot audio cable
* 3.5mm stereo input
* 12-volt wire-free transmission

As well as the bit rate of the encoded file, the quality of MP3 files depends on the quality of the encoder and the difficulty of the signal being encoded. For average signals with good encoders, some listeners accept the MP3 bit rate of 128 kbit/s and the CD sampling rate of 44.1khz as near enough to compact disc quality for them, providing a compression ratio of approximately 11:1. MP3s properly compressed at this ratio can achieve sound quality superior to that of FM radio and cassette tapes, primarily due to the limited bandwidth, SNR (signal-to-noise ratio), and other limitations of these analog media. However, listening tests show that with a bit of practice, many listeners can reliably distinguish 128 kbit/s MP3s from CD originals; in many cases reaching the point where they consider the MP3 audio to be of unacceptably low quality. Yet other listeners, or the same listeners in other environments (such as in a Corvette with "husky" exhausts or at a party), will consider the quality acceptable. It is important to note that quality of an audio signal is subjective. A given bit rate suffices for some listeners but not for others.

Corp_0712_03_z Music_magic Vrfm8 4/8

(MSRP $34.99)

* Transmits all your audio devices including MP3 players, CD and DVD players and your USB Flash Drive wirelessly to your Corvette's FM stereo system
* Features a versatile ratchet neck
* Multi-function buttons: Shuffle/ Random, Play, Stop, Volume and Track Selection Controls
* Last station recall
* Last song played
* Auxiliary audio input for use with MP3, CD and DVD players
* Standard USB port
* Digital LED display for 14 preset frequencies (7 low and 7 high)
* 3-foot audio cable
* 2.5mm stereo input
* 12-volt wire-free transmission

Good encoders produce acceptable quality at 128 to 160 kbit/s and near-transparency at 160 to 192 kbit/s, while low-quality encoders may never reach transparency, not even at 320 kbit/s. In data compression or psychoacoustics, transparency is the ideal result of lossy data compression. If a lossily compressed result is perceptually indistinguishable from the uncompressed input, then the compression can be declared to be transparent. In other words, transparency is the situation where compression artifacts are nonexistent or imperceptible.

However, transparency, like sound quality, is subjective. It depends most on the listener's familiarity with artifacts, and to a lesser extent, the compression method, bit-rate used, listening conditions, and listening equipment. Despite this, sometimes the general consensus is formed around roughly what "should" be transparent for most people on most equipment. Using MP3 audio, it is popular to assume that files with 192 kbps bit rate (44.1 kHz sample rate, 16 bit sample size) should be either transparent or close to transparent.

Storing MP3 Music Files
MP3 music files are in digital format, making them storable and transportable on an assortment of media, including the hard drive in your computer, on CD (particularly for C6 owners), and other removable storage media such as compact flash memory cards, USB flash drives, Secure Digital and MultiMedia Cards, as well as dedicated MP3 players that often have huge internal storage capacities. But how did this all come about, you ask? Good question. Here's the answer.

Corp_0712_04_z Music_magic Vrfm9 5/8

VRFM9 (MSRP $69.99)
* Roadmaster's top-of-the-line model with USB, SD card slots and song-name readouts
* Transmits all your audio devices wirelessly to your Corvette's FM stereo system
* Multi-function buttons: Shuffle/ Random, Play, Stop, Volume and Track Selection Controls
* Last station recall
* Last song played
* ID3 song-name read-out
* Transmits your MP3s and WMAs from your SD Card or USB flash drive wirelessly to your Corvette's FM stereo receiver
* Audio Input for use with MP3, CD and DVD players
* Standard USB port and SD card slot
* Six-position ratchet neck for easy installation and access
* Large, easy-to-read LCD shows 15 preset FM stations (8 low and 7 high)
* 3-foot audio cable
* 2.5mm stereo input
* 12-volt wire-free transmission

Enter The iPod
Unless you're living in a cave somewhere deep in the jungle, you've undoubtedly heard about the iPod, even if you don't really know what it is. The iPod is a brand of portable digital media player designed and marketed by Apple Computer. Devices in the iPod family provide a simple user interface designed around a central scroll wheel (with the exception of the iPod shuffle). The standard iPod model stores media on a built-in hard drive, while the smaller iPod shuffle and iPod nano use flash memory. Like most digital audio players, an iPod can serve as an external data storage device when connected to a computer.

Discontinued versions of the iPod include two generations of the popular iPod mini and four generations of the full-size iPod, all of which had monochrome (b/w) screens, except for the fourth-generation iPod with a color screen (previously sold as iPod photo before it replaced the monochrome iPod in the top line). As of April 2006, the lineup consists of the fifth-generation iPod, which has video playback capabilities, the iPod nano that has a color screen, and the iPod shuffle; all three versions were released in 2005. The iPod is currently the world's best-selling digital audio player. The bundled software used for uploading music, photos, and videos to the iPod is called iTunes. A music jukebox application, iTunes stores a comprehensive library of the user's music on his or her computer, and can play and rip music from a CD. (Ripping is the process of copying the audio or video data from one media form, such as DVD or CD, to a hard disk. The copied data is usually encoded in a compressed format such as MP3 in order to conserve storage space.) The most recent incarnations of iPod and iTunes have video playing and organization features.

iPods originally developed a following among the tech-savvy. Today, Apple's widespread marketing campaigns have led to the iPods' reputation as an easy-to-use, stylish device and dominance among the MP3 market (to the extent that some people erroneously refer to all MP3 players as "iPods"); this has led to a large market dedicated specifically to iPod accessories.

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Here's a 30-gigabyte iPod playing through the C5s stereo system using the VRFM modulator, which is broadcasting to the Vettes stereo on 87.9FM, one of the many available frequencies.

As with any good idea that achieves market success, imitators and competitors were sure to follow, and the iPod was no exception. Virtually every major manufacturer of electronic devices has at least one device capable of playing MP3 files in its product line today, and the ongoing trend is to make these devices smaller while increasing their storage capacity. Which brings us to the main point of this article, Playing MP3 Music in Your Corvette.

While there are several devices available to make permanent connections for attaching external audio devices like MP3 players to your Corvette's stereo system, many of these are expensive and invasive, making them less than attractive and desirable to a lot of Corvette owners. But the good news is there are also inexpensive, non-invasive devices that permit you to enjoy your MP3 music through your Corvette's FM radio without making any modifications or doing invasive installations to achieve this end. These devices simply plug into the cigarette lighter for power, then transmit the MP3 audio to your Corvette's FM radio on any of six or more open and usually unused frequencies. The really good news is that, depending on the model, you're only looking at a suggested list price of from $19.99 to $69.99 for the transmitter. Of course, you have to supply the medium that contains the MP3 files, and this can be an iPod or just about any other portable MP3 player or portable storage media such as a Secure Digital card or USB flash drive, to name but two. You can also connect an external device such as a portable CD player to these transmitters to play the audio through your Corvette's stereo.

Corp_0712_08_z Music_magic Vrfm9 7/8

The VRFM9, shown here, plays MP3 files directly either from SD/MM cards, a USB flash drive, or an external device connected to its aux port. This top-of-the-line unit also displays song-name readout and has a plethora of other features to boot.

How Do They Work?
Actually, it couldn't be simpler. You plug your iPod or other MP3 device from the unit's headphone jack into the receiving jack on the transmitter unit using the supplied cable. you then plug the transmitter unit into the cigarette lighter, turn your FM radio on, and dial up one of the frequencies the transmitter will broadcast to and adjust the volume, tone, and balance to your liking. That's all there is to it.

How's it Sound?
As mentioned earlier, the sound quality of MP3 files depends on a lot of variables including the sample rate, the encoder, and the actual type of audio itself, among other things. There's also another set of variables that are introduced here since we're actually "broadcasting" a signal from the transmitter to the Corvette's FM radio. If you live in an area with a lot of high-tension electrical lines or in a densely-populated urban area, you're likely to experience some distortion or interference that users who are out in the wide-open spaces won't get. This can be compensated to a large degree, however, by selecting another radio frequency the transmitter can send to until you find the one that's best suited to your geographical and urban location.

The ambient noise of your Corvette will also have an effect on the sound quality of your FM-broadcasted MP3s. If you're running a midyear with side pipes, believe me, you're not going to notice any problem with the sound quality, since you're probably going to have your volume turned up just to make out what song is playing in the first place. Ditto for other Corvettes, including C5s sporting Borlas, Billy Boats, Corsas, SLPs, or any other aggressive-sounding exhausts. with these "macho" sounding Corvettes, the MP3 audio imperfections that may be present quickly become non-issues.

How much music is a lot, you ask? Well, here's an example: I have an iPod with a 30 gigabyte hard drive in it, and it will hold 7,500 songs. Do the math-if the average album has, let's say, 15 songs on it, this puppy will hold 500 full-length albums. And it fits in your shirt pocket, the battery lasts about 30 hours between charges, and it's way cool. What's not to love?

Eerybody seems to have jumped on the MP3 bandwagon, and Roadmaster USA is one of the manufacturers producing devices to make MP3s easier to listen to in your Corvette or other vehicle. The company has four models in different price ranges that provide different capabilities. Shown at the begining of this article are the four VRFM modulators that I had the opportunity to spend some hands-on time with.

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At the top is a 4GB USB flash drive, with a 2-gigabyte secure digital card below to the left and a 2-gigabyte multimedia card to the right. The SC and MMC cards are smaller than postage stamps, yet hold hundreds of songs each; the 4-gigabyte flash drive holds double the songs.

In general, the VRFM modulators plug into your Corvette's cigarette lighter to play your favorite MP3, WMA, iPod, CD, or MP3 player music through your car's radio. The VRFM can transmit this high-quality music from an SD (secure digital) card, MMC (multimedia card), USB (universal serial bus) or audio input device, including MP3 players, USB memory key, and CD and DVD players. It can even play any MP3 and WMA music saved on an SD card or USB Memory.

If you are interested in adding MP3 capilility to your Corvette, take a closer look at each of Roadmaster's FM modulator models.



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