Hello Head-Fi,
I'm a PC user that is fairly new to enhanced, non-onboard audio performance and I'm experimenting around. Currently I'm using a Schiit Modi & Magni 2 Uber to drive an HD650 through USB. While I love the sound of the Schiit stack, I'm curious if I'd be able to get audio-processing (e.g. virtual surround sound) into the Schiit stack.
Quick answer: yes you absolutely can. But it will have to be done in software (e.g. Razer Surround, or many (modern) videogames and multimedia applications have their own built-in DSP functionality). The Modi *is* a soundcard, it just connects via USB (and people can yell "USB DAC!!!" all they want - its a USB-based audio interface, as opposed to a PCI-based, or PCIe-based, or FireWire-based, or ISA-based, or whatever - its using USB to connect to the host as opposed to some other interface, with all of the pros/cons of its given bus, and like many other "hi-fi" devices it has extremely limited software of its own). In practical terms, however, its not really much different from other USB soundcards, like say the Asus Xonar U7, it just has less functionality and less robust drivers associated with it (and most of what you're paying for is the actual D/A and analog output sections as opposed to a more jack-of-all-trades device like the U7).
However, if you want to take another interface's DSP features (e.g. lets say you have a stand-alone soundcard, like a Sound Blaster), there is no conventional way to get that output into a USB input, but it *may* be possible to send it out digitally via S/PDIF, ADAT, AES/EBU, etc (whatever) but that depends heavily on the other interface. For example some Sound Blaster cards (and their drivers, this depends on what platform you're on) won't pass DSP features via their digital outputs, but will via their analog outputs, and this is a fairly arbitrary restriction (and its been largely fixed in newer drivers).
My understanding is that, with my current setup, the audio is coming directly from RAM -> through USB cable to the DAC (Modi) -> then Amp (Magni).
That's not quite right. USB does not support DMA, and it's not acting as a "host" anyways. Think of it more like a cheap printer - the host is doing all of the thinking for it, and its just there to be an output device. In the case of the Modi, everything is being handled by whatever generic audio driver that Schiit uses, and the Modi itself is just an output device. This isn't "wrong" or "bad" (at least conceptually) - there's nothing wrong with simple solutions. But it isn't the same as the Modi (or whatever) actually doing "processing" - the era of "fully h/w accelerated" audio is largely behind us, as well, because its mostly unnecessary these days (computers have gotten *really* fast) and (historically) tended to cause more issues than it solved.
Completely bypassing any onboard audio processing.
Again, see above. You're bypassing whatever other interfaces the machine has (e.g. stand-alone soundcard, graphics card with digital audio out, etc) but you aren't bypassing any processing that can be done driver-side, software-side, etc because that's all "above" the actual interface. So for example if you have a videogame that has built-in software audio (e.g. most modern videogames) that's going to exist no matter if you have Modi, a Sound Blaster, etc (whatever) because that's being done in software. If the game requires hardware audio processing (e.g. some older videogames) that won't exist because Modi doesn't support it, and you would need some sort of compatible driver+hardware solution to implement that (e.g. Sound Blaster). If there is hardware processing going on, that's going to happen ahead of the digital output, and still be sent out via S/PDIF (e.g. lets roll back to ~2003 and say you have an Audigy in there, its still going to do DirectSound 3DHW for compatible games, and then spit that output into its built-in DAC *and* its S/PDIF output to connect to an external DAC, and all you're changing is where the actual digital-to-analog conversion takes place, on-card or in some other box).
Keep in mind: for modern operating systems, audio interfaces, applications, etc its pretty much all software-based anyways so the differences between interfaces basically comes down to their I/O capabilities and hardware quality, whereas in years past h/w processing capabilities were also a big consideration when looking at audio interfaces (especially for gaming).
Assuming this is correct: my motherboard has onboard audio (Realtek ALC1150) and has an Optical S/PDIF output. If I used this port to connect to the Modi 2 Uber, would the S/PDIF cable simply be carrying digital (non-converted to analogue) and non-amped data that was processed in my onboard sound chip to the Modi?
All of this about "processing" -
h34r:
This connection would be treating the Modi as a pure D/A converter, and the ALC1150 implementation as the digital source. You'd get its digital output (and the Modi would still convert to analog). Any features the ALC1150 implementation on your system could do, it can output via digital, but ALC1150 is a codec, not a DSP. So most all of its "processing" is also driver-side, but it has significantly more elaborate/feature-rich drivers that do all sorts of other things than basic stereo audio, and the chipset itself is a codec.
Is sound quality going to suffer by doing this? Also, would I lose sound quality through S/PDIF as opposed to using USB?
According to conventional audiophilia, yes it would probably be the absolute end of the world and an entirely unlistenable and unusable source. In reality, I doubt you'd even notice unless you accidentally enabled some feature on the Realtek driver that significantly changes the sound (e.g. the Realtek drivers can include things like equalizers, spatializers, etc that can significantly impact what the output sounds like - you may or may not like the sound but you'll certainly notice a difference). Easiest way to find out: try it and see.
Would this situation also apply to a sound card that has an Optical S/PDIF output (using Optical S/PDIF would bypass the soundcard's built-in DAC and Amp, and go through my Schiit stack)?
Exactly the same except:
A) If the soundcard+driver combination doesn't want to do certain things for certain outputs.
B) Similar to A, if there are certain output modes that the given soundcard+driver combination can only do via its analog outputs.
I think my onboard sound supports 4.1, 5.1, and 7.1 channel configurations, as well as a host of other audio processing.
It very likely does support multi-channel output, but you won't be using that with headphones, especially via TOSlink, at all. Why? Because S/PDIF can only conventionally carry two channels of audio, and only supports multi-channel using proprietary encode/decode schemes (e.g. DTS) which Modi won't support, and which your digital source may not support (not all mfgrs will spring for Dolby Digital Live or DTS: Connect licencing). If you had something that could decode multi-ch from S/PDIF (e.g. a lot of AV receivers can do this) then you could send out 5.1, and then that device would decode + downmix for stereo out (and its usually just going to take the standard coefficient table for this, so it isn't "virtual surround" in any way; things like Dolby Headphone are a separate licence + feature that some devices support). 7.1 is impossible over S/PDIF, and 4.1 while technically supported within the Dolby Digital standard, isn't implemented "the right way" by PCs (they actually don't generally do 4.1, they do 4.0 and assume an external crossover; ditto for 2.1), and even though *that* is also supported within AC-3 (you can send anything from 1 to 5 channels with or without LFE (the .1)) I've never seen it implemented in Dolby Digital Live. The giant purple gorilla of an exception to this is Creative Labs' external stand-alone real-time DTS encoder, the DTS-610, which takes (up to) 6ch analog in, and gives you a 5.1 digital signal out - you could in theory only hook up your 4.0 output and while you'd have a "5.1" signal coming out, only four channels would be active. In practice this is all kind of a pointless way to implement things, because Dolby Digital decoders have to support remapping/downmixing, so its cleaner to just say "okay computer, send out 5.1" and then have your decoder make that work on whatever actual speaker map you have (e.g. 4.1); most DTS decoders can do this too, but some early ones will only do 5.1->5.1 with no remap/downmix ("so why the heck does AC-3 support anything other than 5.1?" -> because it was developed years ago primarily for HDTV, and then appropriated for Laserdisc and DVD, and has to support native content that may not be 5.1, like mono and stereo movies and TV shows, or movies that have Dolby Surround as opposed to Dolby Digital 5.1 tracks in a more turn-key way, and its also more efficient (from a broadcaster perspective) to only send out two channels (bitrates are lower -> you get more channels in the same overall bandwidth), but going from your PC to your decoder none of those concerns are very big, and its just easier to let the decoder do what it does).
Do I even need a sound card to get something like virtual surround?
Maybe. "Virtual surround" is generally always implemented in software, so its a driver-side feature, but you may have to buy [device] in order to get drivers that implement what you want. There are software applications that can support it within their context however, so depending on your usage, it may be the case that only care about that feature for an application (or group of applications) that already do a good enough job on their own, with their own software implementations. However if you want something branded like Dolby Headphone, yes you'll have to buy a piece of hardware to get drivers that implement that stack, as Modi doesn't come with that (it would drive the price and complexity up for Schiit to do something like that, so its reasonable that they don't do it) - Asus makes a lot of products that implement Dolby features. Then you could send that output via S/PDIF to the Modi (or whatever other DAC). Alternately you could send a Dolby Digital Live or DTS Connect enabled source's 5.1 S/PDIF output to a receiver/decoder that has Dolby Headphone (or similar) and it would do what you're after.
Yes; there's lots of ways to skin this cat.
