[SteenWinther]

Can anyone tell this soon-to-be DAC owner if the digital output signal from the computer is provided before or after the DSP? In other words; will any Dolby Headphone or crossfeed plugins and/or drivers work on a standalone DAC?

(This should be a straight forward question, but I seem to have heard various conflicting answers).

Also, is SPDIF and USB handled identically?

Thanks,
Steen

 

[Scrith]

An elementary question, but unfortunately the answer is a bit tricky.

The short answer is that it depends on your sound drivers. To get proper digital output from a digital signal with some special encoding, it cannot be re-sampled, mixed, or manipulated by some DSP service (to adjust for the volume setting in Windows, for example), which usually requires something called "bit-perfect" output from your sound drivers. I'll leave it to someone else to figure out whether your setup is bit-perfect or not.

S/PDIF and USB are probably handled differently on the computer side (sending a USB signal is much different than sending a S/PDIF signal, at some point in the computer hardware/software setup), but should be handled the same on the DAC end (e.g. the DAC gets audio data from one or the other, stores it some common local buffer, then uses it at the appropriate time).

 

[sejarzo]

I don't think it's tricky at all, if you are referring to strictly software-based DSP....which would all be completed prior to the data stream reaching the sound card/audio device, regardless of the interface. Your use of the term "plug-in" seems to imply that you are referring to effects that are handled entirely in software by the player app itself.

However, you threw in the term "driver", too.....does that mean you use your sound card configuration applet to enable some DSP effects that are handled by hardware on the card itself? If so, then there is some question, though I would guess that the S/PDIF output from the card would be from the same data stream that is routed to the internal DAC chip.

No, S/PDIF and USB are not handled the same. A direct S/PDIF output must derived via an internal sound card, while USB is (more or less) just data output. There are several different methods of handling audio streams via USB....."Windows USB Audio Devices" conform to a standard that allows them to be used "driverless", but most are limited to a maximum of 16 bit/48 kHz operation (the Benchmark DAC1 being a notable exception.)

USB audio interfaces that are gaining popularity as sources here, but originally designed to allow notebook-based recording at higher bit depth/rates, generally require their own drivers to handle data transfer to/from the external box. The data transfer can be handled in various modes, each having advantages/disadvantages.

 

[SteenWinther]

Thank you, both.

I am primary interested in whether a stand-alone DAC works with Dolby Headphone as implemented in PowerDVD (software based DSP) and I guess that it will work fine based on your feedback.

But my motherboard (Intel D975XBX with very nice on-board audio) supports Dolby Headphone ON ALL APLICATIONS via SigmaTel drivers under Windows XP. I am, however, now running Vista, so it doesn't matter much to me that this solution probably doesn't work with a stand-alone DAC.

 

[EnOYiN]

Quote:

Originally Posted by SteenWinther /img/forum/go_quote.gif I am primary interested in whether a stand-alone DAC works with Dolby Headphone as implemented in PowerDVD (software based DSP) and I guess that it will work fine based on your feedback.

That is correct. It will work just fine.