| Build quality:Some head units are flimsy
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| | function again.Black out face:When the
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| and weak. Some are built to last. Usually
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| | unit is off, the head unit has a
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| the best way to determine this is by the
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| | completely black face with no visible
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| weight of the unit. Also, check to see if
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| | buttons or controls. Come on. Criminals
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| anything doesn't "fit", or if there are
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| | aren't so stupid that they can't see that
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| parts that are cheap or flimsy. The truth
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| | the head unit still has its face
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| is this: The bigger name units tend to be
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| | attached.Hidden faceplate:This is common
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| better. Also, the more expensive units
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| | for DVD players with screens, and one unit
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| tend to be better. This isn't always a big
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| | that I used to own, the Alpine CDA-7998.
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| deal for everyone, but I believe that
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| | Basically, the face folds into the head
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| build quality is very important.Basic Head
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| | unit, and looks exactly like a unit with
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| Unit Features:Power output:Most head units
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| | the faceplate removed. Neat, but the unit
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| have built-in amplifiers. These drive the
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| | is still vulnerable.In short, all of these
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| speakers. Some head units do not have
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| | tactics are imperfect. Pick the one that
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| internal amps, and therefore, require the
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| | makes the most sense to you, however most
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| use of an external amp. Head units without
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| | units only have a detachable faceplate
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| amps are usually high-end models. Anyway,
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| | feature.CD Changer controls/Optional
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| power is measured in WATTS. We'll talk
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| | equipment interface:This is a feature that
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| more about watts later, but for now, just
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| | allows you to connect other peripherals to
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| see more watts as more volume. Most head
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| | your head unit. These peripherals are
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| units (unfortunately) are deceptive about
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| | often CD changers, digital music players,
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| the power output. Usually, the power
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| | satellite radio units, and video
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| output spec on a unit will say "50Wx4 MAX
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| | equipment. With this feature on your head
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| output". This means that when the laws of
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| | unit, you'll be able to add additional
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| physics are on your side, it's a clear day
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| | capabilities to your stereo system in a
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| everywhere in the world, the planets are
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| | convenient way. However, most of these
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| aligned, the bass hits really really low
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| | interfaces are only compatible with the
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| and hard, and for about a tenth of a
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| | same brand. In other words, you'll need an
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| second, yeah, your head unit will put out
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| | Alpine head unit with the Ai-net interface
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| 50Wx4. However, most of the time, your
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| | connected to an Alpine CD changer with the
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| head unit is probably putting out a
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| | Ai-net interface.Remote Controls:Some head
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| quarter of that. It's not that the head
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| | units have remote control capability. This
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| unit manufacturer is lying, it's just that
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| | is a handy feature because you can control
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| they are exaggerating the truth, AND MOST
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| | the headunit without taking your eyes off
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| PEOPLE DON'T KNOW BETTER. So, anyway, many
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| | of the road.OK, so these are some of the
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| people put a lot of importance on a head
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| | features of head units. Now, let's look at
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| unit's power output. I don't because head
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| | the specs of specific types of head
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| unit amps suck, and no serious car audio
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| | units.Tuner Features:Most head units have
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| person uses the head unit's amp anyway.
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| | AM/FM capability built in. Check out this
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| Most head unit brands have about the same
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| | information on getting the best AM/FM
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| power output anyway. 9 times out of 10, an
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| | performance possible.Presets: This feature
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| aftermarket head unit will put out more
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| | allows you to save your favorite radio
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| power than your factory head unit, and as
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| | stations, and instantly recall them at the
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| such, will sound better.RCA Preouts:These
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| | push of a button.HD Radio: A new radio
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| are used to connect external amps to your
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| | format that is close in sound quality to
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| head unit. These are the same red and
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| | CDs. Basically, a radio station broadcasts
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| white cables that you use for your home
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| | their usual programming, but with an
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| system. Basic head units usually have one
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| | additional signal that can be received by
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| set of preouts (front left, front right).
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| | units with "HD radio" capability. The
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| Some head units have two sets (front left,
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| | availability of units with this feature is
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| front right, rear left, rear right), but
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| | still small, and most radio stations
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| most decent head units have 3 sets (front
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| | haven't yet embraced the technology. I do
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| left, front right, rear left, rear right,
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| | expect this technology to take off,
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| subwoofer left, subwoofer right). One
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| | however because the sound quality is
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| quick note about subwoofer outputs:
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| | better, and not everyone wants to pay for
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| Sometimes they're called "non-fading"
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| | satellite radio.RDS: AKA "Radio Data
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| outputs because they are not effected by
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| | System". A new feature for FM radios. This
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| the head unit's fade control (front to
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| | technology makes it possible for radio
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| back balance). If you're not planning on
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| | stations to transmit text to your
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| adding an external amp, you don't need to
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| | receiver. This text can be used to show
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| worry about RCA pre-outs. If you want to
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| | the station title or the artist name, and
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| add an external amp (or amps), I would
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| | other information.FM Sensitivity: The
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| always recommend getting a unit with three
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| | ability of your unit to tune into a weak
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| pre-outs.RCA Pre-out voltage:Usually this
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| | signalFM Selectivity: The ability of your
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| spec is next to pre-out spec. It is
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| | unit to reject interference from other
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| measured in VOLTS (which we'll go over
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| | stations.FM Stereo Seperation: The ability
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| later). Basically, the higher the voltage,
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| | of a tuner to recreate the proper left
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| the LOUDER the music will be at your amp.
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| | right channel sepearation.CD Players:CD-R
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| Don't look at this as "free power" because
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| | CD-RW Playback: This feature guarantees
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| it is not. In addition, the higher the
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| | that your unit will play a CD-R or CD-RW
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| voltage, the less noise that will be
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| | that was made with a CD recording
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| introduced to your system. Again, this
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| | device.CD-Text: This feature displays CD
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| spec doesn't matter if you don't plan on
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| | text information that is encoded on some
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| using an external amp. If you do plan on
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| | CDs. This information includes artist
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| using an external amp, try to find the
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| | names, song titles and album titles.MP3
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| HIGHEST voltage you can. 2 volts is basic,
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| | WMA/iTunes Playback: This spec assures you
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| 4 is standard for a good unit, sometimes
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| | that certain digital file formats can be
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| you'll see units with 5 volts. I know
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| | played back on certain units.ID3 Tag
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| Eclipse units have 8V(!) pre-outs. In
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| | Display: Displays text (such as song title
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| short, more voltage=less noise and cleaner
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| | and album name) encoded into MP3
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| sound.Digital time correction:This is used
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| | files.DAC: Digital to Analog converter.
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| to simulate a perfect stereo environment.
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| | This device takes the digital signal from
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| If you're at home listening to music, you
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| | your CD, and turns it into an analog
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| want to situate yourself in the middle of
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| | signal for your amp. The better your DAC,
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| the two speakers to get the best sound.
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| | the more "real" your sound will be.CD
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| The same is true in the car, EXCEPT that
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| | Frequency Response: The range of
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| it's a hell of a lot more difficult.
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| | frequencies that the CD player can
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| Usually, the passenger side speaker will
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| | reproduce. It should at least cover the
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| be farther from your ear than the driver
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| | 20hz-20,000hz range.Electronic Shock
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| side. Since sound travels fairly slow
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| | Protection: This feature prevents your CDs
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| (comparfed to light), you'll have one ear
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| | from skipping. If your head unit doesn't
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| receiving a portion of sound before the
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| | offer this, don't buy it. However, most
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| other ear. The digital time correction
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| | players have it, and technology has gotten
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| delays the music slightly so your ears
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| | pretty good lately, so it's unlikely that
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| will be perceiving the same music at the
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| | you'll have any problems with
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| same time. This is a very important
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| | skipping.Signal to noise ratio (s/n): A
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| feature if you are planning an SQ
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| | measure of how well a CD player silences
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| system.Crossover:This feature is
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| | noise. The higher the rating, the less
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| incorporated into many components in a car
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| | noise.Zero Bit Detect mute: When the CD
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| audio system. If your head unit doesn't
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| | player detects a series of 0's on the CD
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| have it, don't worry. Just be sure your
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| | (such as between songs), it will
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| amps have it. Basically, this makes sure
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| | automatically mute the output. This
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| the right speakers are playing the right
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| | feature isn't really important, but is
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| sounds. I will go into more detail about
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| | often advertised.Oversampling: The CD
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| crossovers later.Equalizer aka EQ:This
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| | Audio format has a resolution of 16 bits,
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| feature allows you to tweak the sound. The
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| | with a sampling rate of 44.1khz. What the
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| most basic EQ is a two-band, and controls
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| | hell does that mean? I really don't know,
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| BASS and TREBLE. Some head units have
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| | but think of a digital picture. Zoom in
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| 3-bands, BASS, MIDS, TREBLE. More advanced
| |
| | really close to this picture, and you see
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| head units have 5-band EQs. If you are
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| | pixels. Think of each pixel as a sample.
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| serious about tweaking your sound to
| |
| | When you increase the pixels, you increase
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| perfection, you won't use your head unit's
| |
| | the sharpness and quality of the picture.
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| EQ; You will get an external unit, and
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| | When a CD player has oversampling, it
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| some of these units have 30 bands! I will
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| | takes the 44.1khz, and turns it into a
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| go into much more detail about EQs
| |
| | bigger number. More samples=More realistic
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| later.Theft Deterents/Security
| |
| | sound. Confused? I know. I am too, but a
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| Features:There are a few options when it
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| | unit with oversampling will sound better
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| comes to head unit security:Detachable
| |
| | than one without. Of course, the good news
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| Faceplate:The most common method is a
| |
| | is that pretty much every unit these days
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| detachable faceplate. Basically, you
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| | has this feature.Tape decks:Auto Reverse:
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| remove the faceplate of the unit (where
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| | A feature that will automatically play the
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| the screen and controls are), and the unit
| |
| | reverse side of a tape at the end of a
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| won't function. This will deter thieves,
| |
| | side.Dolby noise reduction: There are many
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| but please don't leave the faceplate in
| |
| | Dolby technologies incorporated into tape
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| your car. Thieves know most people do
| |
| | decks. Most of these features exist to
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| this, and will still break into your car,
| |
| | lower tape hiss, and raise the signal to
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| find the faceplate and steal your head
| |
| | noise ratio.Frequency response: Again, the
|
| unit.Password:Some other units have a
| |
| | frequencies the tape deck respond to.
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| password function. When the unit is
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| | Normal human hearning is from 20 to 20,000
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| disconnected from power, then reconnected,
| |
| | hz.Wow and flutter: This spec tells you
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| the unit will require some sort of
| |
| | how stable the tape deck playback speed
|
| password. The unit will not function until
| |
| | is.Now that you know some of the features
|
| the password is provided.Key CD:A few
| |
| | of head units, you are ready to buy the
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| units use a key CD. Basically, the first
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| | right unit for YOU.Alan Bayer is an
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| time the unit is used, the unit will ask
| |
| | entrepreneur and Car Audio enthusiast. He
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| for a key CD. You insert any CD, and the
| |
| | currently resides in some lame suburb in
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| unit will now designate that CD as the key
| |
| | northern California.He owns an eBay
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| CD. If the power is disconnected, the unit
| |
| | business and the website also have a
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| will ask for the key CD before it will
| |
| | newsletter at my website. Check it out!
|
