Topic: possible solution to using multiple DACs? (Read 13037 times)

Hometownwesty · « **on:** January 04, 2014, 03:19:56 am »

Hi,

I saw at least two threads asking how to use multiple stereo DACs for multichannel sound, and I'm in the same boat.
My initial idea was to use the USBStreamer, but that requires DIY and I2S-capable DACs, so that might not be everybody's cup of tea.
Yesterday I gave it some more thought and came up with this:

How about using multiple zones for sending the same signal to multiple DACs, adapting the audio settings individually and linking them all together?
- for DAC1 all channels except left and right are set to "mute"
- for DAC2 all channels except surround left and right are set to "mute"
- for DAC3 all channels except center and sub are set to "mute"

I tried that yesterday (using a DAC and the onboard sound, as I currently only have one DAC), and it kinda worked, but the video was stuttering, and the sound may have been out of sync.
But since I'm currently using a mock up PC with a jriver trial (to try everything all my ideas out before I invest in new hardware) that my have been due to my setup.
At least the PC is giving me constant trouble, regardless of the above idea.

So could anyone confirm if this was a feasible to use multichannel output via DACs? I don't know of too many multichannel DACs, so this is why I'm trying to go this route.
If all the necessary zones were linked together this should work in an automated type of manner.
And if it should: being able to assign those linked zones a group name would be great.

Any input is highly appreciated.

mwillems · « **Reply #1 on:** January 04, 2014, 10:24:30 am »

Quote from: Hometownwesty on January 04, 2014, 03:19:56 am

Hi,

I saw at least two threads asking how to use multiple stereo DACs for multichannel sound, and I'm in the same boat.
My initial idea was to use the USBStreamer, but that requires DIY and I2S-capable DACs, so that might not be everybody's cup of tea.
Yesterday I gave it some more thought and came up with this:

How about using multiple zones for sending the same signal to multiple DACs, adapting the audio settings individually and linking them all together?
- for DAC1 all channels except left and right are set to "mute"
- for DAC2 all channels except surround left and right are set to "mute"
- for DAC3 all channels except center and sub are set to "mute"

I tried that yesterday (using a DAC and the onboard sound, as I currently only have one DAC), and it kinda worked, but the video was stuttering, and the sound may have been out of sync.
But since I'm currently using a mock up PC with a jriver trial (to try everything all my ideas out before I invest in new hardware) that my have been due to my setup.
At least the PC is giving me constant trouble, regardless of the above idea.

So could anyone confirm if this was a feasible to use multichannel output via DACs? I don't know of too many multichannel DACs, so this is why I'm trying to go this route.
If all the necessary zones were linked together this should work in an automated type of manner.
And if it should: being able to assign those linked zones a group name would be great.

Any input is highly appreciated.

It will depend on the DACs you plan to use, I tried a very similar experiment to the one you're describing with zones, and it did not work well.

As you might've seen in the other threads, if you want to use multiple DACs, the DACs need to be able to sync to each other somehow (through connection to a single master clock, an SPDIF or AES connection, etc.). The ways to achieve this with multiple DACs (i.e. a Lynx AES 16 or DACs that have the digital I/O necessary to support master/slave arrangements) are, for the most part, more expensive than just buying a single multichannel interface.

Trying to output to multiple USB DACs that aren't synced to each other will probably not work. I haven't heard of anyone getting that to work correctly, and myself tried a few experiments with multiple identical DACs on the theory that USB compliant devices "use the motherboard's clock." It was not usable.

There are a large number of multichannel interfaces out there, check out the second post in this thread for some examples of manufacturers: http://yabb.jriver.com/interact/index.php?topic=83870.0. You might want to look through this thread as well: http://yabb.jriver.com/interact/index.php?topic=85141.0

Focusrite makes an 8-analog output interface for about $400, and I can personally recommend the slightly more expensive 8-channel Steinberg UR824.

Additionally, both Asus and Creative make internal soundcards with 8-channels out for much cheaper (an Asus DX retails for around $80 and has 8-channels out). The risk you run with internal cards is that they'll pick up EMI and/or distortion from the computer, which is a non-trivial concern. That said, I used both an Asus DX and an Asus ST/H6 combo and was happy with both, until I got extremely sensitive speakers that made it hard to ignore the EMI pickup. The internal cards can be a good budget solution, especially if you have speakers with a sensitivity in the 80's or low 90's, but your mileage may vary: http://yabb.jriver.com/interact/index.php?topic=86378

Hometownwesty · « **Reply #2 on:** January 04, 2014, 12:27:27 pm »

Thanks for taking the time. That made me understand the other threads better.
So I guess that leaves me with the USBStreamer/currymanDAC option or with using a soundcard, as you mentioned.
Trouble is: I was planning to go with the current NUC, which would mandate a USB-option or going through HDMI to my AVR (even though I wanted to do away with the AVR in the long run.

Thanks

EDIT
Just to clarify: my understanding is that the USBStreamer does the syncing for the DACs and I've seen this implementation twice on the web.

mwillems · « **Reply #3 on:** January 04, 2014, 02:08:36 pm »

Quote from: Hometownwesty on January 04, 2014, 12:27:27 pm

Thanks for taking the time. That made me understand the other threats better.
So I guess that leaves me with the USBStreamer/currymanDAC option or with using a soundcard, as you mentioned.
Trouble is: I was planning to go with the current NUC, which would mandate a USB-option or going through HDMI to my AVR (even though I wanted to do away with the AVR in the long run.

Thanks

EDIT
Just to clarify: my understanding is that the USBStreamer does the syncing for the DACs and I've seen this implementation twice on the web.

I don't have any experience with I2S type DACs, so I can't confirm whether that would work, but I suspect it would.

But to be clear, most of the interfaces in the other thread are external usb or firewire interfaces (i.e. the Focusrite, RME, or Steinberg) so they would work just fine with your NUC; only the Asus or Creative cards are internal.

The USB streamer costs a little over $100, and the curryman DACs are $40 per stereo pair. So for your six channel plus two-out-for-headphones solution you'd be paying $260 plus the price of the enclosure, wiring, inputs, outputs, etc., so probably over $300 and the time and energy to put it together. ~~For $290 you can get a focusrite 18i8 (http://www.amazon.com/Focusrite-SCARLETT-18i8-Interface-Preamps/dp/B00CPCJI2C) which is a USB interface with six analog outputs and two headphone outputs.~~ [EDIT: See below]. If you shop around you could probably find a six plus channel USB or firewire interface on sale at a comparable price (like the ones mentioned in the other thread).

daveca · « **Reply #4 on:** January 05, 2014, 02:11:36 pm »

"I tried that yesterday (using a DAC and the onboard sound, as I currently only have one DAC), and it kinda worked, but the video was stuttering, and the sound may have been out of sync."

It did work. You're asking it to do the job of a rack of PCs.

Thats an extremely busy PC inside... one (two ?) DMA controller(s) handling all that? That's like routing freeway traffic down an alley, to take (SWAG) 6 high speed data channels plus a HD video stream from a parallel DMA path then trying to stuff that massive parallel data into three slow serial USB channels and a video channel...

The problems are:

1. very high video bandwidth
2. 6 audio channels
3. surround sound processing (computer generated/processed) ( see http://documentation.apple.com/en/compressor/usermanual/index.html#chapter=10%26section=0%26tasks=true )
4. latency in communcating with a disc drive (horridly slow and lots of error correction)

Each of those tasks could use its own PC or at least embedded controller (PCI based video and audio cards)

That's a parallel processing problem, especially since surround sound is artificially generated and that takes processing time instead of just pipelining audio and video data down a memory bus.

Try it again and watch the processor and memory usage (especially pagefile), the processor time is probably pegged at 100%

__________________ Q.

What about sending the same audio to multiple DACs?

The identical audio channel to three DACs, for example, without specifying "all channels except this or that one..."

The "except" case indicates all channels are processed for all DAC paths (n channels x m DACs), except the gain for some is set to zero (thats what mute is), thats very complicated.

If the PC is master and DACs are a-synchronous slaves, then all that's required is for the USB controller to send the same data to all DACs.

The several DACs could be on a USB hub instead of multiply-addressed ports. (?)

Whether or not the data sent to each USB port was sent in parallel, or one at a time would be irrelevant as fast as the data transfer rate is inside the PC.

That would eliminate processing, de-MUXing etc which greatly complicates things. (?)

PS the Focusrite box will not work for this, it has no capactiy to play multiple USB output channels except two monitors. ITs a multi channel input recording device. (per user manual) at:
http://d3se566zfvnmhf.cloudfront.net/sites/default/files/focusrite/downloads/9438/scarlett18i8-user-guideen.pdf

It takes u p to 18 inputs, mixes them then plays the recording back in 2 channels.

mwillems · « **Reply #5 on:** January 06, 2014, 09:48:05 am »

Quote from: daveca on January 05, 2014, 02:11:36 pm

PS the Focusrite box will not work for this, it has no capactiy to play multiple USB output channels except two monitors. ITs a multi channel input recording device. (per user manual) at:
http://d3se566zfvnmhf.cloudfront.net/sites/default/files/focusrite/downloads/9438/scarlett18i8-user-guideen.pdf

It takes u p to 18 inputs, mixes them then plays the recording back in 2 channels.

I'm not sure that's correct; the manual indicates that there are six analog outputs which can play simultaneously and are "fully assignable" in software, and I'm pretty sure someone here on the forum has used either this interface or it's little brother (the 6i6) for multichannel output. Could you point to the spot in the manual where it says that it can't play more than two channels via USB [unless they're referring to the headphone outs as the other four analog outs, which would be bizarre]?

EDIT: You're correct, they're referring to the two headphone outs as four analog outs so the 18i8 wouldn't work, but the 18i20 ($409 on Amazon) would work, as would the Steinberg UR824 ($700), or many of the RME interfaces (varying prices). It's odd, the 6i6 is advertised as having 4 analog outs and has four line level outs, plus two "bonus" headphone outs, and the discontinued 18i6 was advertised as having six analog outs, and had six line-level analog outs + headphone outs; but the 18i8 is advertised as having 6 analog outs, but only has 2 line level outs and two stereo headphone outs. That's a really odd inconsistency in marketing.

Sorry for the bad info on the 18i6 OP, but my basic recommendation stands: If you want to keep the NUC, I think you'd be better off from a money and/or time perspective looking for a sale on a 6+ channel USB or firewire interface rather than going the DIY route, unless you happen to enjoy DIY (in which case, full speed ahead).

mattkhan · « **Reply #6 on:** January 09, 2014, 03:14:25 am »

FWIW the cheapest solution, in the EU, I found for this was the focusrite saffire pro 24 which can be found for ~£170 new. It is limited to 6 channel output though so if you need 8 then it's no good. I agree the method of counting inputs and outputs in pro audio interface marketing is typically dodgy and concentrates on making the biggest number possible.

mwillems · « **Reply #7 on:** January 09, 2014, 10:52:50 pm »

It looks like Behringer recently launched two USB interfaces both currently available for $250 over at sweetwater, both with 8 balanced analog outs (the FCA1616 and the FCA610) . I don't know whether they would be suitable as 8-channel DACs or not, as they're still pretty new and I can't find too much info about them, but if they work the same way other multichannel USB interfaces do they'd be the cheapest external balanced option I've seen.

Hometownwesty · « **Reply #8 on:** January 22, 2014, 11:24:34 am »

Holy smoke. Seems that I didn't set my notifications correctly so I didn't even realize the amount of information piling up here and the good care you're taking of me.
Thanks a lot for all the info. That opened up my horizon to a whole load of alternatives (and I was lost already ;-)
I'm not married to the NUC. As a matter of fact I moved away from it a little bit, but I'm changing my mind on a daily basis. Configuring my perfect htpc isn't easy, and I also have a bunch of other questions and issues I need to wrap my head around (see my other threats on TV and such).

You mentioned the need for enclosure etc. as a con, but I actually regarded that as a pro, since it gives me the ability to put everything in a nice custom box.

Meanwhile I'm close to admitting to myself that I'm far from an audiophile and don't have very trained ears, so right now I'm leaning towards buying a motherboard with supposedly good onboard sound, like the Asus, MSI or Gigabyte Haswell Gaming boards, and maybe upgrade later when I'm actually starting to hear differences.
I haven't really ever listened to a good quality system, so some things might be a waste of money for me.
On the other hand I thought I might as well do it right the first time, so I don't have to upgrade as my listening experience evolves.
All this is getting a little over my head. Too many options ;-)
But thanks very much for all your input. I have some more digging to do.

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Author Topic: possible solution to using multiple DACs? (Read 13037 times)

Hometownwesty

possible solution to using multiple DACs?

mwillems

Re: possible solution to using multiple DACs?

Hometownwesty

Re: possible solution to using multiple DACs?

mwillems

Re: possible solution to using multiple DACs?

daveca

Re: possible solution to using multiple DACs?

mwillems

Re: possible solution to using multiple DACs?

mattkhan

Re: possible solution to using multiple DACs?

mwillems

Re: possible solution to using multiple DACs?

Hometownwesty

Re: possible solution to using multiple DACs?