Originally Posted by peekay
My questions about improving the quality of the sound...
1. Do I need to buy a DAC, a DAC+Amp or simply an Amp to improve the sound quality?
Not necessarily. The main problem with portable devices isn't really the DAC, but the amplifier, which is an integrated DAC+headphone driver chip that usually produces around 5mW at 32ohms, and unlike a dedicated amp doesn't have a capacitor bank to have reserve current when louder notes hit. That's still enough to get nearly all IEMs and even some headphones to ear-splitting levels, but loudness isn't the only thing here. Question is how loud do you need them to go, which is a function of the headphone's or IEM's efficiency and isolation over background noise. If you use a very efficient IEM for example that really closes off your ear canal in a room that isn't all that loud, then even that 5mW will be enough. Even if it distorts a bit or the DAC response rolls off (for example my Galaxy S3 sounds too dark and distorts sooner than my iPad2) and it isn't driving the IEM at its absolute best, considering you are working while listening to it, you will probably not notice much difference. Even when I'm not working, for example I'm killing time at a cafe waiting for people, I can easily ignore the shortcomings in favor of portability.
Now you might wonder why people bother using DACs and amps (or a single box that has both). There are some reasons for that:
1. It might be for a fixed reference set-up at home,* where one is only listening and therefore the gains in sound quality can be more easily appreciated, as well as using harder to drive headphones, which at home is easy to compensate for when you have less problems with a bigger amp for it, as well as the likelihood that such a headphone might have an open-back design that leaks sound in and out of it. You can get the signal out of the device, have it processed into analog by a better DAC (which in reality has more to do with the quality of its analog output stage, not the DAC chip on its own), and then its analog output stage passes this signal into an amp (or the amp section in the same box), which does a better job of amplifying the signal.
2. They might be using them more as transportables. Sure they're lugging all that around, but some might listen to them when they get to a location where it wouldn't be a hassle to set them on a table (any of these I tried get too hot when left idling inside a bag, especially some dedicated players like the S:Flo and DX100).
3. For some it may be some kind of a geeky thing to do for this hobby. Do you really need a separate CD transport and DAC, in an age when there are powered DAC designs where the DAC chip feeds the amplifier output stage, eliminating the DAC output stage and preamplifier stage in favor of digital volume control? Do you really need to drive to work in a car with a GT66 turbo or a huge roots-type supercharger? In both examples sometimes it might make sense - you might have just one headphone set-up for home and everywhere else, maybe just a bigger headphone at home; or you have only one parking slot in your apartment/condo.
*What I have at home pictured below; when I'm out of the house, I just use this with either device pictured below. It's more of convenience really, considering that while I still buy physical CDs and keep them on my shelf, CD player transports frequently die on me, while solid state memory doesn't.
Originally Posted by peekay
I have read a bit and am a little confused because how does the DAC change the quality once the sound is at the speaker jack?
It can't. A Digital to Analogue Converter changes the 100011000010110000111110101000000 of your digital audio into an electronic signal that can be amplified by an amplifier driving a transducer like a headphone or speaker, which in turn moves the air to produce the actual sound that you hear. If it's coming out of the earphone jack* on the device, it's already in analogue waveform, since that device has a chip that does both the digital to analogue conversion as well as amplifying it for a headphone.
You mightbe confused about how people are using DACs with MacBooks (and some older PCs) - those have a soundcard that outputs analog and digital signals off the same 3.5mm jack to save space on the chassis. You need a special adapter for this though.
*It's an earphone jack; some speakers just have the amps built into their chassis, so you are technically still hooking up an amplifier to this. Actual speaker terminals on the back of amplifiers have two red and two black binding posts for speaker cables; amps built into teh speaker enclosure still have all these wires, just not the larger binding posts
Originally Posted by peekay
2. If I buy a DAC or DAC+Amp, for the iPod, how is it connected? Is it simply plugged into the Line Out plug (i.e. where the headphone jack is plugged and then the headphones are plugged into the DAC device?
Well, first, go back to what I said above on what a DAC is. If you get a pure DAC you still need an amp for the headphones; if you get a separate DAC and amp, you will hook up the iPod's lineout to the amp, not the DAC, and for smaller devices you might run out of inputs; if you get a one-box DAC+HPamp, make sure it has an analogue input so that you can hook up an iPod's lineout, while using a PC or a smartphone/tablet in its USB input. Now, clarifications on how those can be hooked up.
First, the iPod's lineout isn't on the earphone jack - it's on the 30-pin dock. You need a dock adapter with a 3.5mm jack on it where you can hook up a 3.5mm to 3.5mm cable, or one of those dedicated lineout cables that have a 30-pin dock adapter on one end and a short cable terminating into a 3.5mm plug, like this one. Lightning iDevices do not have this anymore - AFAIK they went for outboard DACs, as there are a lot of iDevice/iOS-compatible DACs that can be hooked up using only the standard data cable (or a short version of it). Note that using the earphone jack output to feed an amp means a few problems since you still have digital volume control going through its amp circuit. You will be getting a louder amplified signal, which may have distortion and other artifacts that the DAC alone doesn't have. You will still end up lowering the volume too far on these and a real line out would probably still be cleaner.
Second, smartphones and tablets do not always have the proper USB implementation in both hardware and software to support USB digital audio streaming. At a minimum, iDevices need a camera connection kit USB adapter to enable digital data transfer (its use for audio was not even originally intended by Apple, but discovered by someone here), as iDevices need a chip to enable such an interface (which is why DACs with "Made for iPod" stamped on it are more expensive as they pay licensing with Apple for these). Androids on the other hand need a USB OTG (On The Go) adapter for very generally the same purpose, but it's the wiring instead of a specific chip. With iOS there are only a few devices, and iOS7 enabled these for the iPhones as well as getting rid of the restriction that iOS6.3.1 put on iPads, however owing to the large number of manufacturers using the Android OS, there are a lot of them that might not have the hardware or software to pull this off. At minimum, some devices might need a specialized player like USB Audio Player Pro (originally Recorder Pro, which had the feature, but they made a dedicated player app for the proper interface and features); others need some more software tweaking; others just won't. For a comprehensive list, check this thread - every five pages there is a list of, or a link to a Google docs link (in the latter pages) with the list of USB audio capable devices and DACs.
On the DAC side, there are also a few issues. Some DACs rely on USB power to run, as they don't have their own power supply. Some DACs might have their own power supply, but run some chips like the USB receiver (and select it by default when activated) or even the DAC off the USB power. Some amps have an auxilliary USB input with a relatively simpler DAC circuit, but may still run that DAC circuit off the USB power, or its receiver chip. Compatible DACs are also listed above.
Originally Posted by peekay
In addition, for something basic, would the E17 be a good start?
The E18 would be better. It's designed as an Android DAC, so its compatibility with Android devices is wider, and you can still use it as a DAC for a PC. It also has an analogue input for the iPod. Note that given the wide range of manufacturers using Android, each using their own hardware design and software, plus carrier software for phones and tablets that can take sim cards, this isn't guaranteed to the same degree as with the "Made for iPod" stamp.
You know what will be simpler? Just get an IEM that won't require more power than what portable devices* require, or at most, get a dedicated player like the Fiio X3 and you will have a little bit more power than the iPod. You can get an IEM that works well enough out of the tablet streaming from the internet since it will use at most 320kbps, but scales well enough that you can notice it does better with the amp on the X3, in which you would have higher bitrate files (320VBR, or even lossless). You can even wait for the Fiio X1 when it comes out later this year since it will only be $99.
*excluding dedicated DAPs that are essentially miniaturized CD players with solid state memory, or DACs with a microSD slot, plus a screen and player interface, which is how the Fiio X3 started.
Edited by ProtegeManiac - 5/20/14 at 8:13pm