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Instead of linking a wikipedia page couldn't you have just answered the question? I have looked for the answer and i couldn't find it that is why i asked here.
Well, he just found it for you, right?
Anyways if you still find the terminologies in the Wikipedia article too confusing or otherwise the article isn't spelling it out well enough, I'll try to make it a bit more concise for you:
(BTW several links in kingoftown1's link will have the same info, just written differently)
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I.
DAC -
Digital to
Analogue
Converter. In terms of music and video, modern copies are in digital code - essentially 1's and 0's - that a computer, loosely defined, has to interpret, which in this case is a DAC turning it into an analog electric signal, that can run the rest of the system up through the amplifier and into your speakers and headphones.
II. DAC can refer to at least two things.
a. The actual DAC chip, which is the single microchip that will do such a conversion within a circuit. Any digital media player of any kind, unless it is expressly referred to strictly as a
dedicated transport (which means all it does is read aloud the 1's and 0's then pass it on to another device to 'interpret), has achip like this, and their architectures vary. An iPod has a DAC, a CD player has a DAC, heck a computer has a DAC in the soundcard.
b. A device that includes a DAC chip, which functions as a separate device that decodes the signal. There are many reasons why this came out separately. From an extreme engineering standpoint, you separate the transport and the DAC to isolate each power supply as well as from each other's noise. Some CDPs have two power supplies, but some may argue the whirring mechanical transport can introduce noise into the sensitive DAC section. From a more practical sense, a separate DAC can turn allow any well-built, functioning transport to sound "good" - an older CDP with a new DAC back in the day (but of course the transport's mechanical parts wear out first), but these days, the variety of potential transports are too diverse - video players, media players, desktop and notebook computers, even tablets and mobile phones (if they have the right hardware and software).
Note : In the same sense, the term transport
is the same way, in that there is the actual transport mechanism that spins your CD's, which all disc players have, and is what a computer drive is;
and in the same sense there is a stand-alone dedicated transport,
which is a CD player or HDD-based player without a DAC in its circuit that passes on the sound. In this sense, a computer used to send digital audio to a DAC essentially becomes a transport device.
III. Function : on a basic fucntion described, that's Pt. I. Now given nearly anything you have that can play digital media has a DAC of some kind, what's a separate DAC - as in Pt. II-b for? Well, some of these DACs have compromises. For one, the DAC in almost all portable players tend to have the headphone amplifier chip integrated into it. That saves space for a device people want to jam in their pockets while holding as much music as possible. Then they run off the same battery that powers everything on that player, like the screen. Ditto a laptop, maybe even some soundcards. A separate DAC will have its own PSU and or battery, and instead of a chip that tries to be the earphone amplifier, where ear- and headphones have a varying impedance from as low as 6ohms to 600ohms, a separate DAC can get the appropriate signal to an amplifier, which in turn should be chosen based on the specs/needs of your earphones or headphones (or speakers, as the case may be).
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...do i just jack my headphones in it or what?...
IV. Have you seen a receiver from, say, the 1970s? How about the 1980s? Home theater receivers? Integrated amplifiers? All of these
are technically, or
have, amplifiers for speakers,
but the terms refer to differences in features crammed into the box. Just like DACs, "amplifier" can be one device or one part of a device. In this case, you can have just a basic poweramp, which requires a preamp and a proper source (a transport and DAC for digital, whether separate or not); a 1970s
receiver has an AM/FM tuner built into the same box; a 1980s
receiver might already include a DAC so it takes a digital input; from (back then) a CDP player; a home theater receiver has a
processor and a preamp to control the amp; what has been referred to as an
integrated amplifier has the amplifier circuit AND the preamp in the same box.
Now look at Pt III and Pt II-b again. When I said the DAC converts the 1's and 0's into an electrical signal, it passes it on to an amplifier circuit, to make it stronger in terms of driving a headphone or speaker. In the sense of how I started Pt IV, you could have a device that is a dedicated DAC, or one that has several circuits in it, in this sense, a DAC and an amp*. Some will have one power supply for both, others will have one each, some basically has a better DAC or a better amp depending on what you're willing to pay for more, either way the amp must be able to drive your ear/headphones.
*
Note : headphone systems' amps refer to, basically, an integrated amp, because they don't usually put the preamp and amplifier in separate
boxes.
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could i get http://www.head-fi.org/products/hrt-music-streamer-ii-high-resolution-usb-d-a-converter and just plug the 3.5mm plugs in it and have it plugged into my PC?
...do i just jack my headphones in it or what?...
V. In the case of this device,
no, you do not just jack it in there. Go back to Pts III and II-b. The analog signal a dedicated DAC and a dedicated amp puts out are not the same. For one, the HRT DAC there makes a 2.25v signal, which is slightly higher than Sony's 16-bit CD standard 2v, with no preamp. It doesn't even have a 3.5mm jack to jack into. A basic CMOY amplifier can probably put out more than that in voltage swing, and even if you use an adapter and find it goes really loud, it's most likely the absence of a preamp than anything else, which is why it might distort, or why it's too loud to begin with. This would be more obvious on a more complex load, ie, a headphone where the impedance varies too far from the stated
nominal impedance that is quoted on the box depending on the dynamic range and frequency it's playing. Also, you may notice DACs and other sources have their analog outputs rated in voltage, while an amplifier's is rated in Watts (or mW for headphones) and voltage is stated in voltage swing, regarding how well it can handle sudden loud notes to sound that much louder over the average loudness of all the rest.
So basically, you'd need an amplifier for that.
