What makes an MP3 player tick?
The chances are you’ve got an MP3 Player tucked away in your pocket for listening to your favourite music when out and about or when just sitting back and relaxing, but have you ever wondered what’s inside one to make it function?
It’s time to unleash one of our technicians to strip down a MP3 player and let you see exactly what’s inside and what makes it work.
Please note this is certainly not something we would recommend you do yourself and it would certainly invalidate the warranty!
This particular player has a front bezel to protect the LCD screen and a metal back to give good protection of the circuitry within.
The first glimpse of the insides of the player itself, here we can see the battery, a few controls at the top and the main circuitry within the player.
Stripping further down, with space at a premium the circuitry is often split across several small circuit boards which are usually linked together by ribbon cables.
With MP3 manufacturer’s trying to cram more and more features into their players so ingenious techniques to split circuitry are often adopted to get as much as possible in a small case.
For example, with this MP3 player there is a total of three circuit boards squeezed into the case. The smallest is right at the top of the player.
This board has switches for ‘hold’ and ‘on/off’ as well as the connections for a small internal speaker, which is barely over one centimetre in size but still gives audible sound.
Unusually, this MP3 player also has a weighed motor attached to give a rumble effect, just like mobile phones, to give some feedback when options are scrolled through and selected.
The next circuit board is mounted onto the front section of the case, and is an array of touch sensitive buttons. A lot of manufacturers have shied away from having lots of mechanical push buttons which can be prone to wear and tear as they get older so with no moving parts touch sensitive buttons have their advantage.
Although over the last year or two, touch screens as part of the display are becoming the favourite means of input on players, more on that later.
By far the largest singe component inside the MP3 player is the battery. With manufacturers striving for the longest playback time possible the more space that can be reserved for the battery to occupy inside the MP3 player the better.
Modern MP3 Players use Lithium Ion batteries and to get the best performance and power capacity it’s best to keep the battery fully charged whenever possible. Unlike old NiCad rechargeable batteries Lithium Ion batteries do not suffer from a ‘memory effect’ and do not need to be fully exhausted before recharging.
The next component has to be the most important, the display. The majority of MP3 players, like the one being dismantled here, use an LCD display – just like a miniature version of what you are used to with your computer. Common sizes range from an inch in size to over 7 inches on some of the larger personal media players.
To get away from having buttons for selecting options, most of the top end MP3 players now have touch screens fitted over the display. There are two types of touch screens available to manufacturers. The first type is ‘resistive’ touch screens which rely on physically pressing down on them and they can detect a single press. The second type is ‘capacitive’ touch screens which detect the presence of a finger on them and can detect multiple presses across the whole screen area.
One advancing screen technology is now emerging into the latest MP3 players are AMOLED displays. Instead of relying on liquid crystal displays with a backlight, each pixel of the screen is made out of 3 light emitting diodes (red, green and blue) which generate the light themselves without having a backlight behind. This results in a far clearer and vivid screen which can be viewed from any angle.
The final piece of the puzzle (or MP3 player rather!) is the main circuit board which contains all the circuitry that does all the hard work of playing the music. The next photograph shows both sides of the main board.
Measuring just over two and a half square inches in size, this is the brains behind the MP3 player.
(1) Headphone Jack – for the sound output
(2) USB Port – used for both transferring music to the player from a computer and for charging the internal battery. Charging circuitry on the board converts the 5 volt supply from the USB to the correct voltage for charging the battery.
(3) Microphone – a common feature in most MP3 Players is the ability to also record so most players will have an internal microphone and some will also have the ability to connect an input via a line in cable to record from other equipment.
(4) Reset button – used to restart the internal processor.
If your MP3 player suddenly freezes or does not turn on then the first troubleshooting tip is to press the reset button. This will restart the internal processor. It’s a common misconception that pressing the reset button will also wipe the music stored on the player but that is not the case – your music will not be deleted by pressing reset.
(5) Processor – this is the heart of the MP3 player. The type of processor used in MP3 players are quite specialised – powerful microcontrollers with a lot of built in hardware for interfacing to the outside world – memory, audio, USB etc.
Here’s the block diagram from the datasheet of the ATJ2236 processor used in the MP3 player we’ve been dissecting which shows just how many functions are achieved by this single integrated circuit – this single chip runs the software on the player, decodes the audio, records incoming audio, drives the LCD display, checks for any buttons being pressed, reads your files from the memory – the list is endless!
(6) RAM – the first type of memory found in an MP3 player is a small amount of RAM (Random Access Memory), which is used as temporary storage by the processor while it is operating.
(7) Flash ROM – the main memory of the MP3 player. This is the memory that is used to store your music, videos, pictures etc.
Depending on the total storage space in the player several Flash memory chips may be used in the design – which is one of the hurdles in creating high capacity players – finding the space to include as many memory chips as possible. The other hurdle is the costs involved for the memory.
Very few MP3 players are now available with hard drives, they are now only used in very high capacity portable media players. Flash memory has a number of advantages over hard drives – no moving parts and reduced power consumption extending battery life.
(8) Memory Card slot – for expanding the storage space for your files. Common types used by MP3 players are SD cards and the smaller micro SD.
It’s always wise to check the type of memory cards your player can
support to make sure you get the right type. For example, there are
now three families of Secure Digital (SD) flash cards:
SD – the original specification was designed to handle up to 1GB of memory, but later expanded to support 2GB and 4GB cards.
SDHC – High Capacity, the second revision of the SD card family. SDHC cards range from 4GB to 32GB in size.
SDXC – eXtended Capacity, the latest family of SD cards – for
64GB and beyond.
And that’s it, the entire MP3 player in pieces. A lot of technology packed into a small device. The only remaining question is who is going to put it back together!