Because the soundcard is not part of the computer. Everything is external. The digital data is sent off-computer. If the soundcard is there to pick it up, great, but it is no longer Windows' responsibility.

If you need to do any on-computer processing, that need to be before any involvement with the soundcard. The final result of that processing is what will be sent to the soundcard. As to whether or not you can reasonably do the particular things you want to do, I can't say, never having had an interest in OtsDJ or anything similar.

Anything done on the computer always has to be pre-soundcard, as far as the main function of a soundcard goes: the DAC. Many PCI cards ALSO has DSP capabilities by virtue of a DSP processor on the card. For them, data must always be routed to the DSP before being sent to the soundcard proper (the DAC). Everything prior to the DAC (where the stream becomes analogue and no longer suitable for any digital processing) must be in computer data format.  USB 1 is much too limited a bandwidth to use for sending digital data (1) to an external DSP, (2) back to the computer (3) back to the soundcard for the DAC. The nearest similarity of PCI cards to USB cards in this respect would be a PCI card with no DSP chip. Such a card would only be able to do what the USB card does.

Virtual Audio Cables is pretty powerful as far as routing data within the computer. It must, of course, be routing the data from some program to some program. It can also route data from a program to your soundcard but that would be the end of it. Output data does not come back from the soundcard for any more computer processing.

It doesn't seem quite correct to call VAC a virtual soundcard.

Virtual Audio Cable is a Windows WDM multimedia driver allowing you to transfer audio (wave) streams from one application to another. It creates a set of "Virtual Cables" each of them consists of a pair of the waveform input/output devices. Any application can send audio stream to an output side of a cable, and any other application can receive this stream from an input side. All transfers are made digitally, providing NO sound quality loss. VAC is a "wave-version" of the "MIDI loopback cable" like MultiMid or Hubi's Loopback drivers.

VAC seems like a set of real full-duplex sound cards with its digital outputs hardwired to its digital inputs.

It doesn't seem quite correct to call VAC a virtual soundcard. It can't process audio data, it only routes it from someplace to someplace else. It may, however, be a means to accomplish what alt_audio wants. I indicated that at the bottom of my first post, although I'm not really sure just what he/she is trying to accomplish.

Its true, VCA makes applications "think" it is a soundcard, but it does not do anything else that a soundcard does. It just routes data from its 'outputs' to its 'inputs.' That's probably why it is named Virtual Audio Cables rather than Virtual Audio Cards.

A soundcard would decode audio, VAC does not.

A card had nothing but an S/PDIF interface wouldn't be actually be a soundcard.

That's ridiculous! Isn't it enough for you that its developer define it as a virtual audio card and that Windows see it as an audio card? What a virtual audio card should do in your opinion, beside feedings audio bits to/from virtual audio ports? Maybe provide virtual sound through virtual air and virtual ears to a virtual brain? Please, give us a break or explain your reasons.

And please stop giving uninformed advices on this forum, like the one about a PCI card being better than a firewire card that in turn is better than an USB card. Why? In which terms? For what application? Maybe only for realtime applications. Certainly not for general purpouse applcations. Please provide technical details and/or ABX testing if you don't want it to be taken as an unwarrented assertion. Otherwise you are just talking about your "feelings". That's something very few people would care about, I guess.

I think that was needlessly argumentative. Nothing Andy said deserved that kind of flame.

Virtual cable vs card is just semantics. (Edit: Both of you need to let this go.)

And PCI vs USB, in the general case and for the average home user, Andy is clearly right. Unless you need USB for some reason, PCI is the way to go. This thread is an example, other problems might be windows games, os support, latency problems, and miscellaneous weirdness from programs that expect the capabilities that normal PCI soundcards have. A USB sound device should only be for laptops, needing portability, or total lack of pci slots -- some of the new pci-e mobos have distressingly few. The only other thing I can think of is a computer with such bad noise problems that only an external device is free of hum, and in that case I would look to find and replace whatever component is causing the noise: it's probably broken.

(I have no opinion of firewire soundcards, having never worked with one.)

As for having to provide ABX tests, he's making usability claims, not audio ones. I don't there's any way to ABX usability. If there was a lot of computer software would be a lot better!

First, it never occurred to me that anyone would take what I said personally. I was seeing this purely as a logical discussion (regardless of the quality of my logic). In retrospect I see that ‘silly' was a poor choice for the adjective. I apologize for any emotional distress I caused.

It is possible to do many ‘virtual' things with a computer. Virtual synths, virtual computers, virtual realities. A virtual computer can do anything a ‘real' computer can do (depending upon the extent of the emulation) although it can not have the direct I/O to the outside world of the primary hardware computer. A software synth will produce real (digital) audio signals, although those needs a soundcard to reach the analogue domain where real sound can exist.

A real soundcard does A to D and/or D to A; it is an I/O device. Anything else is extra, via extra hardware such as DSP chips. S/PDIF, ADAT, and other digital passthrough ports are also just extra. The inputs and outputs presented to an audio application are also extras, not part of a soundcard. They are functions of the driver, a bit of software.

Since the soundcard's function is to translate between two realities, one inside the computer (or anywhere else the digital data may live, such as a stand alone digital recorder), the other outside the computer  a simulation of a soundcard isn't possible in any way I can think of. However, if it pleases someone to think of software as a soundcard, even though it is totally incapable of preforming a soundcard's basic functions, ....

I think most of the ‘why' for my ranking soundcard types have been pretty adequately covered by now. Functionality is my point of view. Decent USB is just as good as PCI from an audio quality viewpoint, but it is considerably more limited in what it can do, even in terms of basic audio I/O.

Firewire does not have the USB bandwidth limitations, and while there are quite a few very high quality firewire cards, firewire cards can't do all the extra on-computer processing that PCI cards can because they are not on the computer. That isn't a real limitation for their intended professional use, but I've seen other threads like this one where people were unhappy with their new firewire card's  inability to do something they used to do via PCI.

Most professional firewire cards are created mainly to contain analogue capabilities within the same unit. These are such things as microphone preamplifiers and advanced mixing boards, things that are too bulky for PCI. From that viewpoint, they are superior to PCI cards, but that is basically a convenience viewpoint. All those capabilities are readily available by using separate analogue boxes.

USB 2 soundcards are now being manufactured. Those I've seen are considerably more expensive that USB 1 cards. They also seem to be somewhat more limited than firewire cards, but do not have the bandwidth limitations of USB 1. They seem to only come in the same flavors as professional firewire cards, with microphone preamps and such.

Now since someone else would probably point it out anyway, I might as well say that this viewpoint might be called somewhat inconsistent. Except for the limited USB 1 bandwidth, and the extra latency one may get off-computer, the why of my ranking is about aspects other than the primary soundcard functions, the "extras" as I labeled them in the virtual section.

The game was fun, but I have no more energy for it now. No hard feelings, I hope.