Do USB or PCI ports bypass motherboard sound chips to get audio from data?

Many external soundcards/processors plug into the USB ports to achieve output, and that output should be as flat as possible. But if they use the onboard sound chip they will never be perfectly flat. They are cheap and inaccurate, falling off before you even consider reaching 10hz, let alone other inaccuracies. So does anyone know how USB/PCI/PCIe generate their audio signals? I imagine they would have to gain the data through binary info, just like I presume a cheap chip would. That would be good for my goals. But I don't know, just don't want to use a port that uses audio from a source that could make me lose info beyond different freqs.
 
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A DAC chip converts digital data (bits) into an analog waveform. The DAC can receive the data from a PCI, PCIe, or USB bus.

An "onboard" sound chip is also on the PCI or PCIe bus, just physically attached to the main board instead of through an expansion card sitting in a PCI slot, or externally connected through a USB port.

Point is all three can have the same physical DAC chip, its the chip and its implementation that matters, not how it is connected.
 

wwenze

Member
2008-03-07 12:46 pm
Audio controller device receives audio data from the driver/OS

Example devices: CM6631A (USB), Sound Blaster X-Fi (To be specific, EMU20K1 is the controller chip)(PCI), or Intel ICH (Integrated, but it is on the PCI bus)

Audio controller devices converts that data, clocks it so that it comes out at the selected sampling rate, and output standard digital audio format (I2S, SPDIF, Intel HD Audio)

DAC takes standard digital audio format and converts it to analogie
 
Many external soundcards/processors plug into the USB ports to achieve output, and that output should be as flat as possible. But if they use the onboard sound chip they will never be perfectly flat. They are cheap and inaccurate, falling off before you even consider reaching 10hz, let alone other inaccuracies. So does anyone know how USB/PCI/PCIe generate their audio signals? I imagine they would have to gain the data through binary info, just like I presume a cheap chip would. That would be good for my goals. But I don't know, just don't want to use a port that uses audio from a source that could make me lose info beyond different freqs.


Typically, you would disable on-board sound in the BIOS if you had a better or preferred sound card permanently attached.

That may not be the case with USB sound cards but if you select output to the USB sound card. you omit the on-board hardware, at least.

After that, there are levels of software and hardware manipulation available depending on the sophistication of the driver and software suite supporting the sound card..... and the built-in capabilities of the sound card itself.

J.