Originally Posted by Ashade
Ok, I'm gonna try to explain it as I understand it, anybody correct me if I'm wrong...
Okay, less of a correction but more like a few additions and adjustments.
DAC: Digital-Analog Converter. Is the responsible of transforming your digital signal to analog signal and this way allowing you to listen to it through your headphones. The quality of the transformation may be good or bad, depending on the implementation of the DAC itself. Each DAC has its own technical characteristics and resolutions. The DAC is gonna be the first bottleneck between your files and the final sound, therefore if you have a very high quality file but your DAC is not capable enough, you will never get the quality of the original file on your headphones.
Most better DACs support 24 bit samples and reach about 20 bits of performance, so can reproduce even the recorded noise on a CD (which you usually do not hear because instruments play a lot louder). A Xonar DX should be pretty close to that and only costs € 65 here.
So a good enough DAC is usually the smallest problem in a hi-fi chain.
Amplifier: Initially it only serves two purposes: 1. Amplify the signal to make it louder. 2. Properly feed the later load (your headphones). There are difficult and easy to drive headphones, and it's something that depends of the frequency you are reproducing. Let's say that the prebuilt amplifier of your phone might be able to drive properly between 3k and 7kHz but it's not able to drive properly in the sub 400Hz region, therefore your music is gonna sound weird and muddy. The better the amplifier the better the sound usually.
1. is voltage gain, 2. is current gain
Depending on the source and sensitivity of your headphones you may not even need voltage gain. In-ears for example will blow up if you feed them 1-2 Volts, many DACs output 2 Volts however.. not to mention what would happen to your hearing.
The better the amplifier, the less it will change the signal (less noise, lower distortion, flatter frequency response etc.). A DAC is actually trying to achieve the same - convert the digital signal into an analog signal that is as close as possible to the theoretically reconstructed signal. This works for most DACs, again, pretty well, up to some point (20+ kHz for CDs for example).
Initially both the amplifier and the DAC should be completely transparent, that means that they should not boost any frequency nor modify their responses (that is what an objective DAC, amp does). In the reality the world is far from being perfect, which means that you are gonna be altering the signal by passing it through several steps. That's why everybody talks about warm or bright DAC's / amps, and even more, some people try to find some sinergy between their headphones and gears (this is something that depends on you, and on what you give the highest emphasis in your equipment).
The idea of synergy is highly problematic. Imho, it's more of satisfying an urge to buy new audio stuff than going at it from an angle that really focuses on an improvement in sound quality.
Lots of what you read in reviews about some electronics being bright/dark/warm/cold etc. is wrong. For example, a reviewer used to an amp with high output impedance (like a receiver's headphone jack) will say a more accurate amp with 0 ohm output will sound bright. It doesn't, it's flat. If anything, you could say it has less bass boost and "sounds" more accurate with a dynamic headphone.
Edited by xnor - 9/13/13 at 12:01pm