Digital Audio Players: Features and Functions

Written by Austin Vaughan in 2004, with contributions from Lone 02/2005

Music Formats
All DAP’s support the standard MP3 format, and most support WMA and WAV files as well. In addition, there are other formats that some players support:

• Audible is an audio-book format used by the popular Audible.com (.aa)
  
• OGG is an open-source format that offers better sound quality at lower bitrates, and has been growing in popularity (.ogg)
  
• FLAC is a lossless compression scheme, so it should sound as good as a pure WAV file, but at a slightly smaller file size (.flac)
  
• AAC is an Apple format with DRM capability. Used as the format for the iTunes Music Store (.mp4)
  
• AIFF is an uncompressed format, like WAV, but used on Mac computers (.aiff)
  

Music Library
There are two approaches to how these DAP’s let you look through the music you have stored on the player. One solution is to show a simple file/directory tree, which is just like how you look at files on your PC's hard drive. You connect the MP3 player to you your PC and it shows up as an external disk in Windows File Explorer. Then you can make directories on the player's disk and copy tracks there, or simply drag the directories straight from your PC. When you use the player, that same directory structure appears on the screen and you can navigate through directories and choose songs to play. You will need to remember where you stored particular tracks because there is no music index.

The other approach is to use the ID3 tag data stored in each music file to build a tag database that the player uses to index the music into useful categories. Mp3 players with an ID3 tag database allow the user to search/browse for music by looking through a list of artists, albums, songs, genres, composers, years, etc. When you add music to the player from a PC, usually with specialized software, the database is automatically updated. Most models use a tag database because it makes it easy for users to search by any category they want, and find a particular song or album efficiently, without knowing where it is actually stored on the player's hard drive. A few players support both types of browsing. It's an important design element to consider since much of your time is spent interacting with the player will be when you are looking through the music that is stored on it. Some people prefer the folder-view type of interface because their MP3s are not properly tagged with ID3 data that stores the Artist, Album, Track name, etc. Files downloaded from P2P Programs like Kazaa often have inconsistent tag data. This can make it hard to find what you want on a player using a tag database, because an artist named "The Doors" and "Doors, The" would show up as two different artists in the list. But there are many ID3-tag editing programs available for download and you can easily correct ID3 tag data fields to suit your preference. If you make your own MP3s from CDs, the ripping program can usually access an internet database, and fill in the tag data for you automatically.

Examples of players using an ID3-tag database: Apple iPod, Dell DJ, Creative Nomad Zen, Rio Karma & Nitrus.

Examples of players using File/Folder-view: all Archos models, iRiver H series, Xclef models, iAudio players.

Examples of players that support both: Archos Gmini series, iRiver H series.

Mass Storage Device support
A Mass Storage Device is an item that you can connect to your Windows computer, and with no additional software of drivers needed, it will show up in Windows Explorer as a disk drive that you can move files on and off of. This is an extremely useful feature since no software is needed, you can simply connect the player to a PC and drag and drop music or data files onto it. Many of the players do require proprietary software to move music and/or data onto a player, which can be a hassle to install on other computers. For instance, at many businesses, Admin privileges are needed to install new software/drivers to Windows, so in some cases, you may not be able to put the application you need onto that PC. Regardless, if your player needs application/drivers to communicate with windows, and you want to use it on a PC away from home, you would need to carry around a CD, disk, or pen drive that has that program, or you may be able to download them from the internet on the target PC. Once the software/drivers are installed, data and music can be easily transferred. Another twist is that some players feature Mass Storage Device support for data files, but still require software for loading music to the player. The software is needed to update the ID3 tag database within the player.

So there are 3 types:

1) Full compliant. No software of drivers needed for moving music and data on/off the player. Examples: all Archos, iRiver, iAudio, and Xclef models, and the Creative Muvo flash/microdrive players.

2) Half-compliant. Mass storage device functions for data files, but requires software to add music to the player's database. Examples: Apple iPod, Gateway DMP-X20.

3) Not compliant. Requires software for loading both music and data files onto the player. Examples: Creative Jukebox and Zen models, Rio Karma, Dell DJ.

Note: Some players, like the Rio Carbon, can create an ID3 tag database without software. When the player is powered on, it will scan itself for new music, and then update its database.

Music Exporting
Because of all the fuss about copyright issues, some players do not allow the user to take the music loaded on an MP3 player and upload them to another PC. You may want to move music back and forth between a PC at home and at work, or at a friend's house, for instance. Some players have absolutely no restriction on uploading music to other PCs, and some do not allow it all. This is often regulated by the interface software on the PC. In some cases, users have developed software to circumvent the manufacturer's restriction. The iPod does not support offloading music from the player, using the software that Apple provides, but a third-party application called Ephpod does support this.

Online Music Stores and DRM
With standard CD prices becoming exorbitant, online music stores have become a recent trend. Basically, each store buys the rights to a record label’s music content, and then legally sells the rights to the buyer, usually at $.99 a track or $9.99 an album. The main upsides with this system are that from your computer you can easily and quickly download from a large selection of music, save about $5 a CD, and remove the ripping process altogether. The downsides; the songs are not uncompressed, CD quality (they’re generally 128 kbps Mp3 or WMA), and many online music services have Digital Rights Management built in to their music tracks.

Digital Rights Management (or DRM for short) is a system that copyrights online content (in this case, music) using built-in encryption. It is used by many online music stores, like Apple’s iTunes Music Store and MSN Music. The DRM solution for many of these services usually limits the number of times a song can be burned on a CD, or the number of times it can be transferred to a certain Mp3 player. It is this aspect that leans buyers toward CD’s; with a CD, you have absolutely no limitations on what you do with the music.

Playlists
A playlist is simply a file that holds a list of tracks to play in the order specified by the user (generally an .M3U file extension). Most players do support playlists that are pre-built on the PC using the software that comes with the player, or by using a third party application like Winamp. Some players like the Apple iPod support dynamic playlists, where you can specify certain fields and parameters for the player to select music from the available tracks. The more popular implementation is the "on-the-fly" playlist feature that some MP3 players support. This allows the user to build a custom list on the player itself, usually by adding tracks or albums to the current list of music to be played. The newly added music will then play in the order the user specified. Some players allow only one on-the-fly playlist, and some lack the ability to remove music or change the order of the playlist.

Examples of players supporting pre-built playlists, and on-the-fly playlists: Creative Nomad Zen series, Rio Karma, Apple iPod (gen3 and up) & mini, Dell DJ, Archos Gmini 400.

Examples of players supporting pre-built playlists, but not on-the-fly playlisting: Rio Carbon, iRiver H Series, Archos Jukebox and Recorders.

Equalizers, EQ Presets
Most DAP’s allow the user to customize its sound characteristics by selecting from a list of preset EQ settings (like Rock, Jazz, Classical), or by making a custom EQ setting. A Custom EQ option allows the user to cut or boost the levels across a set selection of frequency bands, usually 4 or 5 bands depending on the model. DAP’s like the Creative Zen Micro and Dell DJ have 4 band EQ’s, while the Rio Karma offers a more advanced version called a Parametric EQ, which also allows the user to set the mid-point and width of each band for ultimate customization. The most basic implementation of a custom EQ is found in the iRiver H series, which only allows users to adjust Bass and Treble levels. The iPod, in comparison, has only preset EQ settings, and no customizable EQ.

DSP (Digital Signal Processing)
A DSP feature allows the user to change the sound characteristics of the player in different ways than the EQ. This is usually used for simulated specialization effects, to give the music a 3-dimensional quality. Creative players offer EAX effects which can make the music sound like its being played in a concert hall or various other venues. Creative players also have a time-stretch feature which allows the user to speed up or slow down the playback speed. The most popular DSP function is the SRS Lab's WOW effect, which is a surround-sound simulator, featured on several models like the iRiver H series and the Gateway DMP-X20, while the Cowon iAudio series features unique DSP effects like BBE, Mach3Bass, and JetEffect. DSP effects can be software-based algorithms or they can be provided through a chip on the player's mainboard.

Capacity
This is nothing new, but the capacity quoted on a player's spec sheet is not the same as the actual amount of disk space that you will be able to use. The manufacturer specs list the unformatted, total capacity instead of the formatted, available capacity. This is also the standard practice for PC hard-drives. Also consider the firmware files and the player's music database file are often stored on the hard drive, further reducing the storage capacity for music and data. For instance, the 10 GB iPod actually has 9.2 GB of available space.

Sleep Mode
This is related to power management and how the player acts when you turn the device off. A player like the Apple iPod never powers down completely. The firmware is designed so that when you turn it off, the iPod simply "sleeps" until you power it on again. This make for quick power-on (almost instant), but the cost is that the battery is constantly being drained to keep it in the sleeping state. As a result, a player like the iPod will run out of juice in 7 to 10 days even if you never use it during that time. On the other hand some players completely shut down when you turn the power off, and they will not lose battery power in the meantime. But, with this arrangement a device will require an initial boot cycle each time it is turned on, which can be a few seconds or longer. Some players take 10 seconds or longer to get started each time its powered on, but there is no battery drain when off. Some players like the Creative Nomad Jukebox 3 use a mixed arrangement, in that it sleeps for an hour from the time of last use, before completely powering down. It can wake almost instantly if you use again it within an hour of turning it off. But if you use it again after more than an hour, it would have to go through the full boot cycle.

Maximum Playtime
This is a manufacturer-specified number, and actual playback time will vary, usually less. Most companies come up with this time by setting the player to run non-stop, using a low headphone output setting, and using low-bitrate files that require less fetching from the hard disk, which is a major source of power drain. They also seem to take the final figure and round-up to get the Maximum playtime hours, so as to have the best possible specs for advertising purposes. During actual use, most people will search for music, use the backlight, use higher bitrate files, etc., so the actual playtime is almost always less (by 20% or more) then the "Maximum" time determined by the manufacturer. The best way to find the real playback time of any player is to find a forum where it is being discussed by owners and get some direct feedback. Playback time generally ranges from 7-8 hours (Apple iPod mini, Gateway Photo Jukebox) to over 20 hours (Rio Carbon, Creative Zen Touch), with the industry standard at 10-12 hours. Some players like the Creative Nomad Jukebox 3 actually support 2 Lithium batteries simultaneously, which combined can power it for 20+ hours. External battery backs can be purchased specifically or made to increase playback time by twofold or more.

Firmware
All DAP’s have a custom firmware, which is essentially the operating system (OS) for the player; it provides the means to navigate through music, change settings/options, etc. Since the OS for these players is very basic, the firmware file takes up little space on the hard drive. Most players can also be updated with new firmware, either from the player manufacturer itself or from a skilled third-party. These upgrades can do anything from modifying the GUI, to adding support for new audio formats, to even adding the option of video playback. Installing these updates usually involves connecting the DAP to your computer and running an executable update, or by dragging the new firmware file onto the player’s hard drive and then selecting an upgrade option from its menu.

Transfer Interface
Most current-generation players use a USB 2.0 or Firewire interface for high-speed transfers to and from the player. USB 2.0 is backwards compatible with USB 1.1 which most all Windows-based computers support. Mac computers support Firewire natively, but some newer PCs have Firewire ports also. Or, you can buy a Firewire card or USB 2.0 card and install that in a PC as an upgrade. USB2 and Firewire have slightly different specs, but generally transfer at about the same rate. They can load about 1 song per second onto a player. The real bottleneck is the speed of the hard drive, which is slower than the maximum transfer rate of either format. Some older players support only USB 1.1, which is simply too slow for loading music onto players with 1 gigabyte or more capacity.

Hard Drives
At this point in time there are three different sized hard drives used in DAP’s: 2.5", 1.8", and 1". These drives are produced primarily by Toshiba, Hitachi, and Seagate. These are all smaller and more shock-resistant than the ones in desktop PCs. Hard drives are precision mechanical devices, not as tough as flash memory, but they are durable. My iPod has survived at least 2 dozen nasty spills and still runs like a champ. I take it mountain biking, no problem. It is certainly possible for a drive to fail after one hit, or a few, or for no apparent reason at all, but failures are generally uncommon and a drive should last many years. I would expect 3 years of service with regular use, and maybe 5 with moderate use. It is also possible the drive will be running in 20 years.

Display
While most DAP’s use simple monochrome (black and white) screens to navigate music/settings, the newest bunch feature bright color screens, not unlike those found on most modern cell phones. The two most popular types of color screens are TFT and OLED. TFT (Thin Film Transistor) LCD screens are known for providing a bright, clear picture with the aid of a backlight. On the other hand, OLED displays don’t require a backlight, consume less power than TFT screens, and are less costly. TFT screens can be found on players like the Archos Gmini 400 and the Apple iPod photo, while OLED screens are typically used on small flash players.

Navigation Controller
There are several types of control mechanism used for navigating through menus and lists on a DAP. Most controllers are speed-sensitive, so that the faster you move the controller the faster the cursor moves through lists on the screen.

• Touch-wheel/Click-wheel. A circle on the face of the iPod that resembles a tire laying flat on the ground. With a selector button in the center. Move a finger around the wheel clockwise or counter-clockwise to move the curser on the screen up or down. Only Apple players feature this design since they own the patent. Efficient and precise. Newest iPods (gen4 and mini) feature click-wheels, which include tactile buttons underneath touch sensitive wheel.
  
• Touch-strip. A skinny touch sensitive strip on the face of the player designed to be used with a thumb. Moving a thumb or finger up and down moves the cursor up or down on the screen; thumb or finger can also rest on one end of the touch pad to scroll up or down without additional movement. Double tapping will usually select the highlighted item. Good for scrolling through lists quickly, but sometimes too sensitive. Found on players like the Creative Zen Touch and Micro, and iRiver H10.
  
• Barrel-wheel. A mechanical wheel on the face of the player that resembles a wide tire on a axle, mounted horizontally. Like the center wheel on a PC's mouse, but wider. Usually sunk into the face of the player so it doesn't stick out too far. Use the thumb to roll the wheel up or down to move the curser on the screen. Current implementations also allow you to click in the barrel-wheel to make a selection on the screen. Some implementations also use it for volume control. Intuitive. Players with this controller include Gateway DMP-X20, Dell DJ, e.Digital Odyssey 1000.
  
• Scroll-wheel. Another mechanical wheel, but usually thin like a coin, and usually mounted to the side of a player. Similar to the wheel on a PC's mouse but thinner. Rotates 360 degrees. Roll it up and down to move the cursor on the player's screen. Can usually push in the wheel a little to select an item on the screen (click-select). Players with this include Creative's Nomad Jukebox 3 and the original Zen, Rio Karma & Nitrus. May have to
  
• Joystick. The same kind found a typical video game controller. Allows for an additional plane of movement than wheel-controllers. Can have click-select capability as well. Players with this include the iRiver H series, Rio Karma and Nitrus.
  
• Thumb-pad. Usually a 5-way, mechanical pad, like a square laid flat on the face of the player. Up, Down, Left, Right and click-select. Basically functions like a joystick. The Xclef HD800 has a pad like this.
  
• Scroll-switch. A mechanical switch usually mounted on the side of the player. Looks something like a scroll-wheel, but it doesn't rotate 360 degrees. Spring-loaded to return to its normal position. Push the switch up or down to move the cursor on the screen, then let your finger off the switch and it will stop scrolling through the list. Has click-select like the others. Used by players like the Creative Nomad Jukebox 3, Entempo Spirit, and on LCD remotes from Cowon iAudio and iRiver.
  

Battery
Most players have a built-in battery that is rechargeable, but not removable. This is done to keep the size, weight, and cost of the device to a minimum. Batteries are Lithium-ion or Lithium-polymer and should last 300-500 charge cycles or more. It is better to keep the player charged as much as possible and avoid fully draining the battery, in order to prolong its life. With some players, it is possible to change out the battery when (eventually) it dies, though it usually requires disassembly of the device. Some companies will change out the battery for you, for a charge. Apple charges $100 for battery replacement outside of warranty. Replacement batteries for several models (including the iPod) are available at [Linky] for about $50 each.

Few DAP’s offer an easy accessible removable battery port to swap different batteries. Creative's Jukebox and Zen models, iRiver’s H10, and Gateway’s Photo Jukebox are several that do. Extra batteries for these players are available from the manufacturer, usually for $50 or less.

Player Dock
A dock is a desktop device-holder that primarily functions as a convenient PC interface for the DAP. It usually stays near the PC, always connected to that PC by standard cabling. The user can simply pop the player into the dock in order to connect the DAP to the computer. Most people find it easier than connecting the player by wires every time. The dock may also support features not available on the player itself. The iPod dock has a line-output, as does the Rio Karma dock. The Karma's dock even adds an Ethernet interface, while the iRiver H10 dock has a compartment to charge its spare battery. Few players even have a dock available, and the ones that do exist are often only available as an additional accessory. The dock may require power (Rio Karma) or it can be a passive device (iPod).

Remote Control
An in-line remote is a small controller that attaches by wire to the main body of a DAP, and the headphone cord is then attached to the controller. It allows you keep the DAP in your pocket or backpack while clipping the controller module to your shirt or jacket. Usually the player has a special headphone port with an adapter that accepts the cord from the remote. The remote may come with the player or some companies sell them as accessories.

Most in-line remotes have only basic control features, like Play/Pause, Next/Forward, Previous/Rewind, and Volume Up/Down. Creative offers a remote for some of their players that has an LCD screen to display the song title, and it adds FM radio/recording capability as well. iRiver makes a remote (for the H series) that has an LCD and controls capable of navigating all aspects of the player, and Cowon’s iAudio M3 uses a similarly featured remote as well with an even larger display.

Do note that not all players are capable of supporting an in-line remote, usually the cheaper ones. The Rio Karma is a funny case in that it was built with a special connector to support an in-line remote, but the company never made one.

Line-Out
A true-line out is supposed to be a separate output port with a low-level signal that has not been routed through the player's internal amplifier or DSP chips. This is so the user can patch a pure stream from the player into a higher-quality amplifier, like a headphone amp or home stereo. The reason for this is because the internal amplifiers on most portable audio devices are tuned for power conservation, and they can be noisy compared to an external amp. The line-output signal can be either analog, optical (digital), or SPDIF digital (electric) depending on the model. Because these are portable players, the line-output is usually through a 3.5mm mini-jack port. The Rio Karma is the only one with RCA outputs, on its dock.

Not all players have a line-output port, and some that claim line-output don't actually produce a true line-level signal. A true line-level signal should not be affected by changing the volume or DSP/EQ settings on the player. Some players have an option to set the headphone output to line-output, using the same headphone port, but this is not a true line-out signal. Players with false line-outputs include the iRiver H series series, the Gateway DMP-X20, and the e.Digital Odyssey 1000. The Creative Nomad Jukebox 3 is widely considered to have the best line-outputs.

Generally, the line-out feature is reserved for more expensive models because it is the audiophiles that care about it. Most people are content with using the headphone output and a patch cable to play music through a home stereo, or their car stereo, or whatever.

Memory Buffer
The memory buffer is an internal flash memory module that caches music from the hard disk drive during playback, to help reduce power drain and extend playback time. Without a cache the player would have to constantly fetch from the hard drive, which is usually the largest source of power consumption in a player. Generally, the larger the memory buffer, the better, since it can hold more tracks in memory and fetch fewer times from the hard disk. Theoretically this should increase maximum playback time, reduce normal wear and tear on the drive, and reduce the number of opportunities for the disk to get scratched when you are moving the player around. But, in reality, it is not that simple. Caching is controlled by the firmware, which can be optimized in various ways. The cache may be constantly refilled, or it may not refill until its nearly depleted, or some mix. "Skipping" during playback is not really a factor like in CD players, since even with a small buffer like the Archos players (2mb), there have been no reports of this. Also keep in mind that a larger buffer does not always mean a longer playback or any other tangable benefit. For instance the original Creative Nomad Zen has a 16mb buffer and 14 hour playback, while the new Zen NX has an 8mb buffer and 14 hour playback. It appears that in some cases like this, manufacturers have reduced the buffer size to keep production costs at a minimum, especially if they found little benefit with a larger cache. Some players like the Apple iPod have a larger 32mb buffer, but because of other factors (small battery) still have a short playback time (3rd gen iPod gets only 7 hours or so).

Voice recording
Several DAP’s offer this feature, usually from a small built-in microphone on the unit. This lets you use the DAP to take almost unlimited voice notes since they are stored on the hard drive. The format is usually a low-quality WAV file that can be played back through the DAP or transferred back a PC later, although some players allow you to choose the format and bitrate to record in. Players that support this feature usually have a dedicated button so one-touch recording is possible. Some players may also have a line-input, and an external mic can be used to record voices or anything else.

Line-in Recording
This is a feature whereby the player can make audio recordings through a direct connection, usually a 3.5mm input jack, and usually the player can encode the audio to MP3 in real-time. This feature can be useful when "ripping" a CD into MP3 files, by hooking up the output of a portable CD player to the input of the MP3 player/recorder. It’s mostly useful when a PC is not available, or to record a live performance from a self-powered microphone or even the soundboard. Some players offer gain adjustment on the recording level if the source is too loud or too quiet. Most offer only Mp3 encoding (usually up to 320 kbps), but some DAP’s like the Creative Nomad Jukebox 3 and iRiver H series players can record in uncompressed .WAV files. Uncompressed files can be transferred to a PC for more professional encoding to MP3. It is generally agreed that while onboard recording/encoding quality can be quite good, the best way to encode MP3 files is still using a PC with the EAC and LAME software combination.

FM Recording
A handful of newer players that include a built-in FM radio also support recording directly from a specific FM station. DAP’s like the iAudio M3 use one-touch FM recording, while newer players like the Creative Zen Micro and iRiver H10 allow the user to program a time and station for which the player can record. This feature is marred somewhat by hard drive spinning noise caught on the recording, but the quality is adequate for saving radio talk shows and sports broadcasts.

Built-in FM Transmitting
A popular DAP accessory these days is the FM transmitter, a device that plugs into the player, lets the user pick an FM frequency, and then broadcasts audio from the device to it. Though other options like cassette adapters and Aux-in ports on car stereos offer better sound quality, sometimes an FM transmitter is the only option for car audio (if the stereo is built in and has no cassette adapter or Aux-in). It’s rare to find a DAP with a built-in transmitter, but the most notable are the Neuros I/II and the Samsung YP-910. Some flash memory players can also broadcast to an FM station with an attached antenna.

Warranty
Most players come with a warranty against defects, usually 90 days or 1 year. If the player dies outside of that range, you are out of luck. The company may agree to try and fix the player if you send it to them, but the charges are often as much as it would cost to buy a new one. So, it may be a good idea to buy an extended warranty at the time the DAP is purchased. Usually, extended warranties are not a good deal for the consumer, but for portable audio gear, it's probably a good bet. Most people will inadvertently drop their DAP from time to time, and usually a DAP will survive, but if it doesn't, what you have left is an expensive paperweight.

Best Buy offers favorable warranties, but you have to pay retail price and tax to get the player. Personally, I don't go for them. I'd rather buy my players online and save the money. All my players have survived at least one 1-meter fall, and my iPod has taken more than 20 spills. No failures yet.

Apple products come with a one-year warranty, and they offer an extended warranty (AppleCare) for an additional charge. Archos products also come with a one-year warranty, but it's rare that someone can get them to honor that warranty. I would advise looking at a company's customer service record and taking that into account before buying one of their products. Amazon.com customer reviews is a good place to check.

Also of note, custom modifications to the DAP, either internal or external, will generally void the warranty. Mod at your own risk.