Help me understand soundcards

[Chris V]

I know a little bit about soundcards, mainly that soundcards in PCs are pretty cheap and poor sounding and that external soundcards like the Fireface are often quite expensive but good.

My question:

Are there circumstances where a sound card is avoided completely with certain types of DAC?

[PeterSt]

With USB connected DACs, yes.
I thought you just bought one ??

that external soundcards like the Fireface are often quite expensive but good.

Maybe it wasn't your subject, but I don't think any soundcard is good as such. Anyway the FireFace is not IMO. It is good at passing through SPDIF, and it is good at it for several reasons, one of them it being an external soundcard.

Of course I can't know how all soundcards sound, but usually the higher grade soundcards like Fireface, Lynx and a few more, end up sounding the best in their leage. I'm fine with that, but a dedicated DAC made for good sound sounds better. Theoretically a 1200 euro (or whatever it is) 56 channel with (not all channels) 192/24 soundcard can't sound "good" if compared with a 2 channel DAC that's more expensive. Also, I don't think DACs are over-priced as long as they are in the 1000+ leage. A lot of development and knowledge goes into it. I know ... 

[Chris V]

With USB connected DACs, yes.
I thought you just bought one ??

Nope the Shek D2 has switchable SPDiff and optical inputs.

Regarding the soundcard, I think the penny has just dropped for me. I had failed to appreciate that their main job (for sound out) was to serve as a DAC, and once you have a DAC elsewhere then it is not needed. .

The same applies to the fireface. I was confused because it is called a soundcard, but as you explain its best applied just to 'convert' firewire to SPDiff and not use the internal DAC (which is naff).   

OK that begs another two questions.

1. When a DAC is fed by USB is there some sort of internal conversion to SPDiff inside the machine.

2. Whatever is this 12S I keep stumbling across

[PeterSt]

Hi Chris,

1. When a DAC is fed by USB is there some sort of internal conversion to SPDiff inside the machine.

That completely depends on the DAC. E.g. the TwinDAC+ does so indeed, the CrazyT does not. Just two examples from the same house.
Keep in mind that reasons can exist for these disgn decisions, like the TwinDAC+ allowing for both SPDIF and USB connections, and the CrazyT being a "standalone DAC" actually not needing anything than a disk to feed it with data, that not being possible with SPDIF (and added to that a certain type of USB connecting that just does).

2. Whatever is this 12S I keep stumbling across

I2S is an internal protocol for transporting music (PCM) data. "Internal" means : from one IC (like receiver chip) to another (like the DAC itself). It is a most RAW (meaning lossless) connection, a bit similar to SDI connections for video which are found on the better devices (I mention this so you may understand when you know about SDI). I don't think I2S can be an external connection, or maybe a very short one. Anyway, as you can imagine this is not done anyway, because no other devices could connect because it's no "external" standard like SPDIF is. But, suppose you'd have a CDPlayer with I2S output and a DAC with I2S input, it would be the best connection possible.

Oh, and note that different "protocols" can make use of different functionalities. E.g. SPDIF is one way traffic (the receiver e.g. cannot tell "please send again, something went wrong"), whereas USB does have two way traffic. Whether this is utilized by the USB DAC is another matter, but the CrazyT should because it's normally error-corrected reading from disk.


Btw, do not get blind of avoiding the soundcard, thinking that USB is *always* better. I'd rather put it some other way around : since USB DACs are relatively easy to produce, most often you end up with a poorly design, though "cheap" (read : not all the attention was put to it, that could).

Peter

[Telstar]

But, suppose you'd have a CDPlayer with I2S output and a DAC with I2S input, it would be the best connection possible.

I would like to stress this

Not considering firewire, USB to 12S woud be the second best. But a good reclock in the DAC (like  the one in the TwinDAC) can help minimize the jitter.