1. Wait, isn't the N900 a portable music player already ?

Sure, it is. Just like any other modern mobile phone, tablet, and of course specialized digital audio players (DAP) like the iPod, iRiver, Cowon and other devices.

All DAPs or PMPs have the following components :

• a battery :-)
• storage: preferrably lots of it, as internal Flash and/or SD card, to store your digital music, generally in compressed form (as MP3 or FLAC files for example).
• media player software to let the user interact with that collection of files
• most often (but not always) a screen, to display information (playlists, tags etc.)
• a user interface to command the software: hardware buttons and/or touch-screen
• more software bits (called codecs) to decode the compressed format being played and turn it into an uncompressed digital stream (PCM). These codecs determine which files your DAP will be able to play (mp3, flac, alac, wma, etc.).

All these are needed just to select a file and play it.
Up to now, everything happened in digital format, just "bit-shuffling", and it doesn't really matter how it was done, as the resulting signal is always the same.

Now, for sound to actually come out in the real world, we need to "go analog", which means a few more components :

• a digital-to-analog converter (DAC) : electronics (often just a chip) that turn the digital stream (zeroes and ones) into an analog signal (continuous waveform of varying frequencies - think sine waves)
• an amplifier : more electronics to turn that weak analog signal into something powerful enough to move at least a pair of earphones
• a jack socket and a volume control :-)

Note: when you play music through your computer, the exact same things happen, the DAC/amp part in this case being your computer's "sound card" (actually most often a chipset nowadays).


2. So, what is an "audiophile" portable music player then ?

If all you need is background music for running, riding a bike, bus or train, and generally shut out noise from the outside world, any device will do, quality-wise. What you will be looking for is size, weight, battery life, ease of use, ability to play your files, insulation, etc.

But if you have good-sounding Hifi equipment at home, and listen to your mobile player in the same quiet conditions, you will likely notice a huge difference in quality between the two.

If you want or need better, near-Hifi sound on the go (say, you spend a lot of time in hotels), bridging that gap means entering a new world, mostly made of costly compromises :-)


3. But what makes sound worse or better ?

Most of all, the "source", ie the contents of the file you're playing. If it's bad, no amount of technology will make it good... The original sound itself may be the cause (old recording, bad mixing etc.), but more often it comes from careless or excessive compression : a 128Kbps mp3 file will never sound as good as the original CD, no matter what. From here on we'll suppose we have a good source, like a clean rip of a CD in a lossless compression format such as FLAC.

Next in line is the DAC : digital-to-analog is where a lot of the stuff happens. It's surprising how much better a good DAC can make the same file sound, compared to run-of-the-mill chipsets found in your regular PC or laptop.

Then there is the amplification stage, which adds its own problems. Noise, hiss, non-linear frequency response, sound coloration, etc. Also, if you are using good headphones which happen to have high impedance (see below), it might yield good sound but simply not have enough juice (power) to drive them correctly...

Last of course are the earplugs/earphones/headphones : if you use tin cans in/on your ears, the best source+DAC+amp in the world is going to sound like a tin can :-)

Both ends (sources and *phones) are under your control. The real issue is having a choice of DACs and amps.


4. How does that work in practice ?

At home, rigging a HiFi setup that will get a nice, clean, clear sound out of your digital music is neither difficult nor overly expensive (if you're not an "extreme audiophile", that is :-).
Your files will generally be on a PC or laptop. This gives you the first six bullets in part (1) above : power, storage, media player, codecs, and UI. As long as everything stays digital this is just fine.

The main trick to better quality is to bypass the computer's built-in DAC/amplifier (the "sound card"), to extract the original digital signal and process it somewhere else. This is made very easy with USB, which all computers have.

There are lots of external DACs on the market, some standalone, some coupled with a headphone amp. They come in all shapes, sizes, and prices.
Just plug one into a USB port, and the system (Windows, Linux, OSX) will detect it and automatically redirect its digital sound output to it. That's all. Your music will then be converted to analog by the external DAC and amplified for your phones by the external amp.

Even entry-level DAC/amps make an incredible difference (with good sources and phones, of course).
The bottom line is that you get to choose each stage of the sound processing, mix and match, try out different things, upgrade this or that as you wish.


5. Why is the "portable" situation different from the rest ?

Well, the "P" in DAP/PMP stands for "portable", so that's what the market offers : the whole enchilada in one pocketable package. Yes, the tiny Sans Clip+ actually has all nine components described above, including screen and up to 40GB of memory, in less than 4 by 6 centimeters :-)

Again, most of the time that is perfectly fine. It is, however, an all-or-nothing proposition : when you switch from an iPod to a Cowon J3 to a Samsung Galaxy to anything else, you are forced to buy a new screen, new storage space, new UI and controls (with new bugs :-), etc.

And if you are willing to sacrifice some portability for better sound, it's even worse, because you have no choice of components. There are a few "audiophile-oriented" DAPs on the market with truly superior sound quality (and prices), but it's a niche market, catered to by small specialist outfits. The results sound great, but tend to have unacceptable downsides compared to mass-market products, especially for the price : limited memory and/or battery life, user-unfriendly and/or incredibly buggy interface, poor support being the main ones.

So the logical way out would be to use a run-of-the-mill device only for the digital part, like the PC, then extract the signal and feed it to the portable equivalent of our DAC/amp combo above... These do actually exist. Unfortunately, given the state of the mass-market devices, using them like this is most of the time impossible, or very difficult.

The first hurdle is that the mobile device must have a USB Host port, which is not common at all. Those few that do are mostly Android devices, but the current Linux kernel in Android does not have USB sound support like the PC version does. This may change in the future, but right now the situation is dismal...


6. Good old N900 to the rescue ?...

My N900 is old but in good working condition. I'm not using it as a phone anymore, so it's open to experiments :-)

Thinking about this stuff I realized it had great potential as a DAP : 32 GB of internal memory, plus SD card, a nice screen and UI, Linux-based and hackable, able to run a number of multimedia apps, etc. And also the same hurdles as the rest : a non-Host USB port, and a crippled kernel...

But one of the defining (and endearing) qualities of the Maemo community, since 2005, is that it doesn't take "No" for an answer. So I thought there might still be hope, and this project was born :-)