[Bohemianism]

I've been reading about computer audio but I'm still a little confused about it all. I'd just like to see if my understanding is correct, also if some of my questions could be answered that would be great.

The DAC. I understand what it is and what it does. What I'm confused about here is the connections. Well a USB connection is simple. What what's Toslink, or Coaxil or all the other methods of connecting it to the computer?
Do that all connect into to Line Out/Headphone/Speaker jack, just with different chords?
Also which connection is the best?

Secondly with an speaker or headphone amp, if I'm not connecting it to a DAC, but straight into the computer how does it connect?

Lastly and my major source of confusion. Soundcards.
When would you need an external soundcard over the built-in soundcard, using my Macbook Pro (generation before the new unibody Macbook Pro's) as the example.
If your using a DAC and an Amp, is an external sound-card obsolete? What does the sound-card do these other components don't?
Oh and regarding 5.1 surround sound, I gather an external soundcard would be needed (if your using a Macbook Pro's soundcard). But if you're using an amplifying is one still needed to handle 5.1 audio?
All and All soundcards confuse me. Why would someone get an external soundcard over getting a dedicated DAC and Amplifying.

Sorry for that jumbled set of queries. I'd be a great help if someone could answer them as if their talking to an idiot (me), so I don't get lost.

 

[Bohemianism]

No-one can help shed some light on my confusions?

 

[Currawong]

The different connections are just that, different connections for sending digital data:

Optical, which is what your MacBook Pro has, is built into the headphone socket, and uses a plastic or glass optical cable. On the back of CD players and the like, the plug/socket is called a Toslink socket (as it was designed by Toshiba). On your MacBook Pro, it's a "mini optical" socket. It is limited to 96/24 resolution, which is better than USB.
Coaxial uses an RCA jack, rather like you use to connect hi-fi components. It has no limits.
USB is USB, but is limited to 44.1/16, CD resolution basically.
AES/EBU uses XLR jacks, but apart from cable impedance, is the same as coaxial.

A sound card usually does some combination of translate the digital into analogue (and vice versa). It can possibly also output the digital signal in one or more of the above methods.

With 5.1 sound, the digital signal is different to regular 2-channel digital, so indeed you'd need, externally, something that handled it. For example, in Audio Midi Set Up (in /Applications/Utilities) you can set the optical output on your MacBook Pro to "Encoded Digital Audio" which will cause it to output a 5.1 signal, if appropriate.

Your MacBook Pro, when a mini optical plug is inserted into the headphone socket, will automatically switch the socket from being analogue to digital, and the settings you can use or not will change appropriately.

Does that all make sense?

 

[dmashta]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif Optical, which is what your MacBook Pro has, is built into the headphone socket, and uses a plastic or glass optical cable. On the back of CD players and the like, the plug/socket is called a Toslink socket (as it was designed by Toshiba). On your MacBook Pro, it's a "mini optical" socket. It is limited to 96/24 resolution, which is better than USB. Coaxial uses an RCA jack, rather like you use to connect hi-fi components. It has no limits. USB is USB, but is limited to 44.1/16, CD resolution basically. AES/EBU uses XLR jacks, but apart from cable impedance, is the same as coaxial.

just a slight correction - usb is capable of 24/96.

as to which is better, that's debatable and will depend on the particular implementation of your components. in general, i'd say coaxial is preferred, followed by toslink and usb, the latter two being more arguable as far as "better" goes. more likely than not, which method you use will depend on what you have available. going with your MBP, you'll be limited to either toslink (mini toslink via the headphone out) or usb. but i suggest you don't worry about that when starting out.

the sound card provides the D/A conversion and headphone amplification so it does what a dac+amp will do. in other words, if you choose to use an external dac/amp, it will replace your sound card. why you would want to go with an external dac and amp is because built-in sound cards (especially those in laptops) are usually mediocre at best.

 

[Currawong]

Quote:

Originally Posted by dmashta /img/forum/go_quote.gif just a slight correction - usb is capable of 24/96.

True, I should have mentioned that. However, there are very few devices capable of supporting it unfortunately.

 

[Bohemianism]

Thank, for that it's really helped.

So you wouldn't really need to use an external soundcard as well as an external DAC and Amp, unless you want use the different connection methods that may be available on an external soundcard?
Also if you wanted 5.1 sound (which I don't I'm just trying to take it all in), would you need an external soundcard that could handle it, and then a DAC, and amp if you choose to?

 

[dmashta]

Quote:

Originally Posted by Bohemianism /img/forum/go_quote.gif Thank, for that it's really helped. So you wouldn't really need to use an external soundcard as well as an external DAC and Amp, unless you want use the different connection methods that may be available on an external soundcard? Also if you wanted 5.1 sound (which I don't I'm just trying to take it all in), would you need an external soundcard that could handle it, and then a DAC, and amp if you choose to?

a dac+amp IS your external sound card. they're the same thing. if you choose to get a dac and amp then that's all you'll need (that will be your external sound card).

same thing goes for 5.1.

 

[Currawong]

You could look at this way for simplicity: A sound card is something that acts as a digital to analogue converter. It can be in your computer or not.

The confusion probably comes when you have sound cards which have digital output (so they aren't converting anything except the connection) and DAC/amp combos which are amplifiers with a DAC (sound card) built in.

I think the naming confusion comes as for a long time, PCs didn't come with sound cards by default, or required them to be an add-on card. Also most PC motherboards only have fairly basic audio built in. If you want digital output (or audio that wasn't crap) you have to buy a dedicated sound card. Some people just bought something that does the same job, but is in an external box connected via USB. Thus people tend to call boxes such as the M-Audio Transit or EMU0404 (which plug in via USB) an "external sound card". Since it's not a card at all, but a box, I tend to call them external audio interfaces.

This confusion doesn't exist in Macs. It's just "inbuilt audio" or "external audio interface" for us. That all Macs have Firewire (except the new MacBook) and optical out makes things more flexible too.

Maybe the solution is to look at any device according to its functionality and where the digital signal is converted to analogue.

 

[obobskivich]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif You could look at this way for simplicity: A sound card is something that acts as a digital to analogue converter. It can be in your computer or not.

a sound card is not synonymous with a digital to analogue converter, a digital to analogue converter is a part found on a sound card, however the sound card will also have DSPs, ADC (or a CODEC, in place of separate DAC/ADC components), and on newer soundcards, DRAM, theres also some very complex software that goes into a soundcard, compared to something as simple as a PCM DAC


Quote:

The confusion probably comes when you have sound cards which have digital output (so they aren't converting anything except the connection) and DAC/amp combos which are amplifiers with a DAC (sound card) built in.

actually the sound card/DSP is still handling format conversion and decompression/compression, consider Dolby Digital Live output, the DSP is still taking the 5.1 from the "ether" of software, and putting it into a format that a D/A using an AC-3 decoder can actually make sense of, theres still quite a bit going on using digital output, the only thing you're NOT doing, is using the built-in D/A and opamps

Quote:

I think the naming confusion comes as for a long time, PCs didn't come with sound cards by default, or required them to be an add-on card. Also most PC motherboards only have fairly basic audio built in. If you want digital output (or audio that wasn't crap) you have to buy a dedicated sound card. Some people just bought something that does the same job, but is in an external box connected via USB. Thus people tend to call boxes such as the M-Audio Transit or EMU0404 (which plug in via USB) an "external sound card". Since it's not a card at all, but a box, I tend to call them external audio interfaces.

most modern ATX/BTX derived PC motherboards have some pretty complex audio circuitry built in, almost all ATX and all BTX derived boards will offer at least 6ch audio from a media controller on the southbridge, and at minimum a 6 out/2 in CODEC, more complex solutions have gone as far as integrating Envy24 or EMU10k into the board, and providing discrete multi-ch DACs and stereo ADCs, keeping the entire lot above 100 dB SNR, and that kind of solution is starting to be seen more and more in the enthusiast segment

as far as USB streaming audio is concerned, it depends on what the device actually does, USB DACs and amps require pre-processing done by the computer, using the CPU, as they can only accept the rough equivalent of LPCM input via USB (this is all handled by the host operating system in real time, although its very inefficient for 3D audio, compared to using a discrete DSP (as the CPU is a general purpose processor, it can handle audio processing, which is generally very repetitive, an area where DSPs (anything from VIA's Envy24 to nVidia's GT200) excel greatly)


Quote:

This confusion doesn't exist in Macs. It's just "inbuilt audio" or "external audio interface" for us. That all Macs have Firewire (except the new MacBook) and optical out makes things more flexible too.

just because you call it a mac doesn't mean it doesn't have to obey the same rules as PC hardware, as its all the same componentry (even the Motorola based boxes, plain and simple), what I mean here is, the same exact things are going on the background, even if you don't ever see them, yes, the hardware offers you FireWire and optical S/PDIF, that doesn't make the platform any different, as these are merely additional features, they also don't make it any easier or harder to understand (well, if you let the Apple store shop for you, its easier

)

Quote:

Maybe the solution is to look at any device according to its functionality and where the digital signal is converted to analogue.

perhaps, but if this is your solution, why are you calling an orange an apple and a pear a strawberry?

now, to honestly answer the OP's questions:

you will require a DAC regardless of what solution you go with, and it always exists, a sound card, or "external audio device", will have the DAC alongside DSPs and various other components (as mentioned above), a discrete external DAC (here, if you want me to name things by what they do) will accept an LPCM signal in, be it from USB streaming audio, TOSLINK S/PDIF, or coaxial S/PDIF, which has to be provided from a digital output source (we could say transport, but a rose by any other name...), meaning your sound card or "external audio device" (whatever you chose)

as far as sound cards go, all personal computers ultimately have one, it may be in-built (such as the MacBook Pro digital and analog outputs, these are all provided via a CODEC (afaik, as it would keep costs, power consumption, and footprint down, which would be the largest concerns for a notebook, in that order) which is connected to the Intel ICH that also controls your disk drives, and some other components)

however you end up connecting your system, you'll basically come down to having an analog output, which will then be fed into your amplifiers

5.1 is no different, its just a more complex DSP to handle it, a more complex CODEC or DAC (or multiple less complex DACs), and some pretty good compression schemes (AC-3 and DTS as opposed to mp3 and ogg vorbis, stuff like that)

to get 5.1, the optical output MAY support this (I honestly don't know, or feel like finding out), however if it doesn't, you would need an "external audio device" which is capable of 5.1 or 7.1 output, this won't be a straight DAC mind you, this will be a processor, such as the M-Audio FireWire 410, or Creative's USB based X-Fi (which, afaik, is not Mac compatable)

hope this helps explain the reality of computer audio, and if you've got any more questions, feel free to lemme know

cheers

 

[Currawong]

Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif a sound card is not synonymous with a digital to analogue converter, *SNIP*

None of that is simple, nor disagrees with what I've written, but good of you to make the effort to write it up.

 

[obobskivich]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif None of that is simple, nor disagrees with what I've written, but good of you to make the effort to write it up.

my point is, the last dozen or so threads I've read, its a noob (not saying you're the noob in this thread) saying some E-MU or Creative external card is a DAC and asking for comparison to a FUBAR or VDA or something

just trying to explain the hell out of it, hopefully someone benefits

 

[Currawong]

Fair enough. I don't claim at all to understand the convoluted workings of what has to be done in Windows XP to get decent audio. I do blame the PC world for the confusion.

 

[obobskivich]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif Fair enough. I don't claim at all to understand the convoluted workings of what has to be done in Windows XP to get decent audio. I do blame the PC world for the confusion.

I'd actually point the finger more at the specialist press, like PC World magazine, Maximum PC, etc which basically serve as mouthpieces for Creative's marketing related to whichever product is "in"


honestly its more that people jump into it thinking ANYTHING that isn't inside the PC is "just a DAC" and anything that IS inside the PC is a "sound card", its wrong and it raises or lowers expectations of a given piece of hardware, so I'm trying to explain away from that line of thinking

 

[Bohemianism]

obobskivich, I think I get it, a soundcard can also process signals. Using my Macbook Pro as an example, take the audio from a DVD and handle 5.1. Whereas just an external DAC, can only do conversions to signals the computer can normally handle? For most regular purposes (I say most because there's usually exceptions) is that correct?
Also you may want to use an external soundcard as an interface (not sure if that's the correct word), allowing different types of connections? Like audio coming into the computer? Is that also correct?

But if I just wanted the best digital to anologue conversion for listening t music, a dedicated, hifi purpose DAC would be best. Correct?

Still one this that confuses me.
Say I had 5.1 speaker setup connected to an amp connect to the computer (there may be other components connected along the way). Would I need an external sound-card to handle the surround sound signal (if my built in soundcard coulded handle suround sound signal), or could the amp handle that process?

 

[obobskivich]

Quote:

Originally Posted by Bohemianism /img/forum/go_quote.gif obobskivich, I think I get it, a soundcard can also process signals. Using my Macbook Pro as an example, take the audio from a DVD and handle 5.1. Whereas just an external DAC, can only do conversions to signals the computer can normally handle? For most regular purposes (I say most because there's usually exceptions) is that correct? Also you may want to use an external soundcard as an interface (not sure if that's the correct word), allowing different types of connections? Like audio coming into the computer? Is that also correct? But if I just wanted the best digital to anologue conversion for listening t music, a dedicated, hifi purpose DAC would be best. Correct? Still one this that confuses me. Say I had 5.1 speaker setup connected to an amp connect to the computer (there may be other components connected along the way). Would I need an external sound-card to handle the surround sound signal (if my built in soundcard coulded handle suround sound signal), or could the amp handle that process?

I'm quite lost reading through this

for surround sound, of any type, you need some form of decoder, be it the cheapie codecs included in most modern PCs (including most macs, I won't say all because a lot of current laptops only offer stereo audio and I'm entirely unaware of the abilities of the mac mini/all-in-one units)) or a very expensive discrete processor

this decoder has to be connected to your multi-channel source, for example connecting a DVD player with digital output to a receiver with digital input, the receiver is decoding the multi-channel signals, as well as performing D/A conversion

while stereo requires the same process, its much less complex (basically due to copyrights, in a nutshell) and more or less any device will support it (theres also that "surround sound" has only existed since the early 1980's while stereo has existed since sometime in the 1950's or 1960's, if not earlier, and consider that since the 1980's, we've seen about two dozen format changes in the name of impetuous marketing for surround sound)

for pure fidelity, a decent USB based D/A is fine, for surround sound, you'll need something capable of surround sound, for example an external sound card, of course confirm that it supports multi-channel output

the "amp" which you've so wonderfully blackboxed onto a pedestal is nothing more than a wire with gain (could I be any more vague and generalistic? really?), its pretty "dumb" to what signals are going through it, the more channels you have, the more amplifiers you need (wow, I actually got more vague!)