High-Speed or Low-Power?

[ggking7]

I recently started paying attention to how my amp and computer are powered and I'm amazed at what a difference power makes. I thought increasing a music server's performance would be the key to increasing sound quality, but now I'm wondering if decreasing the amount of power a computer uses could be more important. Has anyone experimented with an ultra-low power music server?

 

For example, I've found that using my dual-core CPU in single-core mode sounds noticeably better. Could that be due to the lower power consumption?

 

[The Computer Audiophile]

Hi ggking7 - This is very similar to the C.A.P.S. pc I wrote about.

 

http://www.computeraudiophile.com/content/Computer-Audiophile-Pocket-Server-CAPS

 

[ggking7]

Thanks Chris, I just read it. Very nice article. Of your 13 requirements, I'm only interested in sound quality, although cost is important too.

 

Have you heard of anyone testing different software or hardware configurations to determine if low power consumption and high sound quality correlate?

 

I'm intrigued by the Power over Ethernet and external 12V capabilities of the ITX board. Have you heard of anyone comparing the sound quality of different ITX powering methods?

 

[matan]

 

ggking7 wrote:

Have you heard of anyone testing different software or hardware configurations to determine if low power consumption and high sound quality correlate?

 

 

I tested this rather extensively about 18 months ago. Based on my experiments, low power wins over high CPU speeds every time when it comes to audio. The average contemporary CPU can handle all of the processing required for audio playback in its sleep :-).

 

Having lots of GHz handy does nothing good for you, as it draws lots of current and generates lots of heat. Both are bad news; generating a high-current, low-noise power supply is much harder than a low-current, low-noise one. Heat isn’t our friend either: you need to get rid of it, and fans are bad for audio and electrical quality (just ask the listeners of the 2nd Computer Audiophile session last year, we demonstrated the same server with and without a spinning fan – and it made a huge difference). The CPU power-scaling features are a mixed blessing for audio applications, as they only partially reduce TDP.

 

Power over Ethernet is a nice concept but it’s not a good idea for pristine audio quality, because the power supplies inside the network switches are typically cheap (read: not very quiet) and the Ethernet cable used isn’t typically shielded. I would go with a quiet linear or switching power supply (one with a high switching frequency would be better).

 

 

[ziggyzack]

This should come as no surprise, but how can you be sure it's just cpu power which makes a difference? And what aspect of cpu 'power' is problematic - raw gigahertz? Operations per second? Some other measure?

 

Hard drives spin at varying speeds - would constant velocity be any better than variable speed hard drives (i.e. avoiding the higher torque needed for spin-up)? Would SSDs be any better? I read recently that computer memory is a relatively major EMI emitter. I don't know anything about it, it could be nonsense, but it poses the question to what extent reading purely from solid state memory is advantageous.

 

Modern systems have increasingly aggressive memory clocking, where DRAM runs at multiples of the cpu clock. Is DDR2 memory better than DDR3?

 

Modern OSs run multiple tasks in the background. Does that make a difference? To what extent can these tasks be turned off? Would you disable antivirus, and leave your music collection vulnerable, for the sake of better SQ? Would it give better SQ?

 

Does the amount of on-chip cache have an effect? And then there's the power supply...

 

I've no idea whether this is all a collection of red herrings, or not (but I've got a pretty strong suspicion they're not!), but there's no reason, as far as I can tell, why computers should be considered hi-fi components and should be anywhere near a hi-fi system. This is why ethernet dacs must be the way to go. Aside from the fact that 1) ethernet has been designed to stream asynchronous data, at a rate far exceeding that required for high quality audio, it is also 2) designed to operate at a range far exceeding that of USB, firewire, spdif, or any other connector I know about. Another huge advantage 3) is that, as a general networking protocol, the control options are excellent, as the controller can also be divorced from the player.

 

With an ethernet dac, the server can be a NAS or computer tucked away in a study, under the stairs, or installed in a loft, to give three possibilities. I.e. anywhere but the living room or music room. The ethernet dac itself need have no moving parts (solutions with built in hard drives are severe compromises). All that is required is an ethernet port, control logic, a dac chip (or chips) and you're done. It still contains electronics, but these can and should be designed specifically for the task and no more - further, the case design and power supply design can address the separation of analogue electronics from digital. The hi-fi stack can then be fed clean power, if desired, without pollution of any kind from a PC.

 

While it is admirable to try to get the very best from a PC, it's also futile - there are better designs and architectures out there, and it would be great if people were more aware of them, asked more about them, and demanded more of the manufacturers currently working with different interfaces. The more good systems that can play 24/192, the bigger the market for studios to release really well recorded and mastered music.

 

[The Computer Audiophile]

Hi ZiggyZack - Wow there's a lot to address in that post but I'll stick to your comments about DACs with an Ethernet input. It may seem like I'm busting your chops all the time, but I'm not purposely targeting you. As we've discussed before, I get the sense you are pulling some of this out of thin air. Your statements could be much more valuable if you'd offer some information to back your opinions.

 

 

 

"All that is required is an ethernet port, control logic, a dac chip (or chips) and you're done."

 

That's quite an oversimplification. I am a huge fan of DACs with an Ethernet port (Linn DS players) but there is much more to it than you suggest. On the Linn unit I reviewed I found the Ethernet input to sound a bit inferior to the coaxial S/PDIF input. I think there is a lot of improvement to be made in terms of handling the data entering the DAC via Ethernet.

 

 

"While it is admirable to try to get the very best from a PC, it's also futile - there are better designs and architectures out there, and it would be great if people were more aware of them, asked more about them, and demanded more of the manufacturers currently working with different interfaces. The more good systems that can play 24/192, the bigger the market for studios to release really well recorded and mastered music."

 

Can you please list some of the "better designs and architectures out there" and let people know about the units they're "unaware." I'll currently put my PC music server up against any one of the "better designs and architectures out there" and not worry about it sounding inferior. Is it possible your comment about futility has more to do with your lack of knowledge in this area and how to get better sound?

 

[matan]

Thanks, Chris, for echoing my sentiments. I couldn't agree more, and most of the Ethernet DAC designs today are based around the traditional DAC model with an Ethernet front-end. It certainly works, but as you said there is still a ways to go regarding SOTA.

 

To you, ZiggyZack:

 

[...] but how can you be sure it's just cpu power which makes a difference? And what aspect of cpu 'power' is problematic - raw gigahertz? Operations per second? Some other measure?

 

It's not CPU's computational power that makes the difference - it's the stuff around it. Faster CPUs have more transistors which draw more current, and they need faster chipsets, which means more frequency dividers, more current for those chipsets, and higher EMI. The higher frequencies also mean that more energy is radiated from the copper traces on the motherboard because the copper ends up being somewhat of an antenna at gigahertz frequencies. The higher TDP (heat) causes an increase in the overall temperature of the system, and that increases resistance and entropy (noise) - so you need even more current.

 

More power = more noise = more heat = more cooling.

Noise = bad.

Heat = bad.

Cooling = bad.

 

It's a vicious cycle and as you said I only touched the tip of the iceberg, but the point is that decoding and displaying 1080p video requires MUCH more computing power than anything 2, 5.1 or 7.1 channels, and, by analogy, you don't fit a Ferrari engine to a scooter just because you can.

 

Your comment about mechanical HDDs is somewhat irrelevant - all mechanical hard drives spin at a constant angular velocity. Some designs (WD in particular) do change the rotation speed but that is only within a few discrete speeds and to accommodate different loads. Besides heat and vibration, the main problem with mechanical hard disks is the current transients that happen when the armature moves across the platters - the mechanism is quite similar to a speaker transducer -- it is even called a "voice coil" -- and that can induce undesired electrical noise. Hence, SSDs tend to introduce less noise, although their memory access and control logic can also harm the sound. That said, any decent design should be able to decouple the storage from the playback, as is done by a variety of products, both current and pending.

 

As you mention, current consumer operating systems are not ideal for audio reproduction because they are non-deterministic. The multiprocessing architecture allows (for example) the defragmenter to 'wake up' and start toiling, possibly in the middle of your listening session. Highly undesirable. The aerospace and medical industries have this down pat - by designing preemptive, real-time operating systems... and even then they screw up some times!

 

Finally, I totally agree with Chris about a computer-based system being able to smoke any other design. Put it to the test, you won't look back!

 

Enjoy the music,

 

Matan

 

 

 

[ziggyzack]

It looks like you're completely agreeing with me, then at the end you say you'll stick to computer based. I think you've misunderstood.

 

The design I propose as best, from the point of view of separation of hi-fi components, is that of an ethernet dac. It's still computer-based, just arranged better.

 

You still have a computer and you still have an interface. Music is stored and served by a computer. The computer streams the music via an ethernet connection to the ethernet dac. So the computer can be a normal, dedicated computer, cheap as chips. Nothing special and not some computer/hi-fi hybrid attempt, because it can be kept away from the hifi, say in another room. The ethernet dac can be as wonderful as you like. Think of it like a CD player, except instead of a CD drive, music data arrives via the ethernet port. And instead of control buttons on the dac, you control it via the network using wifi (so there are iphone control points, android control points, etc.)

 

I don't think I need to explain it like that, but I don't understand... if you agree that computers aren't ideal, why wouldn't you agree that the approach I describe is the best possible solution?

 

[Audio_ELF]

ziggyzag commented... "The design I propose as best, from the point of view of separation of hi-fi components, is that of an ethernet dac. It's still computer-based, just arranged better.

 

You still have a computer and you still have an interface. Music is stored and served by a computer. The computer streams the music via an ethernet connection to the ethernet dac. So the computer can be a normal, dedicated computer, cheap as chips. Nothing special and not some computer/hi-fi hybrid attempt, because it can be kept away from the hifi, say in another room. The ethernet dac can be as wonderful as you like. Think of it like a CD player, except instead of a CD drive, music data arrives via the ethernet port. And instead of control buttons on the dac, you control it via the network using wifi (so there are iphone control points, android control points, etc.)"

 

As far as I'm aware, there are no systems like this - at least not at a high end level. The only possible system that comes close is using an AirPort Express with a DAC, or you could set up a Linux type system using NetPort.

 

UPnP devices are NOT network DACs.

 

Eloise

 

[ziggyzack]

It may seem like I'm busting your chops all the time, but I'm not purposely targeting you. As we've discussed before, I get the sense you are pulling some of this out of thin air. Your statements could be much more valuable if you'd offer some information to back your opinions.

 

Can you please list some of the "better designs and architectures out there" and let people know about the units they're "unaware." I'll currently put my PC music server up against any one of the "better designs and architectures out there" and not worry about it sounding inferior. Is it possible your comment about futility has more to do with your lack of knowledge in this area and how to get better sound?

 

The better design (I was talking about system design, not individual components) was the one I had just described. Logitech, PS Audio, Linn, Resolution Audio are examples of manufacturers who support it.

 

As for the rest, well... As I've said before, when you've asked me before, I'm an interested punter with a bit of experience, just like you. I don't know what information I could give you that would possibly back my opinions. Hopefully people will see them to be internally consistent - the only way to establish credibility on a forum.

 

On the subject of pulling information out of thin air, your comments on the Majik DS-I review missed the mark. In fact, you missed a great deal of the point of the product. The DS-I is the integrated version - it's a one-box system with what Linn call a Digital Stream player, multiple inputs, a pre-amp and a power amp. None of the other products in the range have a pre or power, they are DS players only (actually they have a smaller player with integrated amp, but without multiple inputs). These all have an ethernet input only. The spdif input on the DS-I is there for flexibility on their integrated unit, but their top range units use only ethernet in. This from a company with more hi-fi and engineering clout than most (they reject spdif for the well-known clocking issue - with ethernet, the data is delivered asynchronously, so the buffer output and dac are timed by the same, local, clock).

 

So please do not question my background when you managed to miss such a critical piece of the design in that in-depth review. And then deliver platitudes like 'I think there is a lot of improvement to be made in terms of handling the data entering the DAC via Ethernet'. It's up to you if you preferred the sound of spdif, but that's quite a claim. I don't think Linn have gone back to the drawing board, somehow.

 

[manisandher]

"... I totally agree with Chris about a computer-based system being able to smoke any other design."

 

I'm currently having a nightmare trying to optimize the AES interface to my DAC.

 

In your experience, what's the best way to interface the computer with the DAC? I'd really love to hear your thoughts...

 

Cheers,

Mani.

 

[ggking7]

In the hopes that it would increase sound quality, I optimized my Linux system for low power usage by turning on all power management features I could find in both the BIOS and the kernel. I also removed all unnecessary hardware components from the system including Blu-Ray player, 1 of 2 memory sticks, wireless card and video card. I also left the case open and unplugged the CPU fan. To my dismay, it sounded worse. I would describe the sound as "edgy" and not pleasant, similar to (if not the same as) brightness. I meticulously tested each component of the change, hoping that some of the changes were positive and some were negative and I would be able to narrow down the positive ones, but the entire experiment was a failure. It sounds best without any of the changes I made.

 

Previously I went through a different series of experiments where I optimized the system for super-low latency. I employed the real-time kernel patch and used jack's real-time capabilities with mpd. It was worse even after much finagling. I tried rtirq. It was worse as well.

 

After these failed experiments, my conception of computer playback is changing from one of potential optimization, to one of potential de-optimization. I had hoped that I would find a certain aspect of computer playback that "really matters" to sound quality, and I would then be able to increase sound quality by optimizing the system around that aspect. Instead, I'm starting to think of computer playback as something that is relatively easy to set up optimally (at least on a Linux system), but can be easily de-optimized.

 

I'm working out a list of the items that, in my experience, are necessary in order for a Linux computer system to be set up optimally for playback.

 

matan, how can you use a linear power supply with a computer? Is there a particular one that works?

 

One other thing I wanted to ask. If noise is what we're battling, why not use a filter (PS Audio Duet for example) on the computer's power supply so noise from the computer doesn't get back into the same electrical circuit as the other audio components, and isolate a USB DAC from the computer with a USB->optical->USB converter? That way the computer can make as much noise as it wants, it won't find its way out either end, right?

 

[ggking7]

Mani, could you start another thread about that, or send matan a personal message? Let's keep this thread on-topic.

 

[ziggyzack]

As far as I'm aware, there are no systems like this - at least not at a high end level. The only possible system that comes close is using an AirPort Express with a DAC, or you could set up a Linux type system using NetPort.

 

UPnP devices are NOT network DACs.

 

For example, the Klimax DS (11 grand's worth of high end!). Note the UPnP AV support:

 

http://www.linn.co.uk/files/d04af758/KlimaxDS_infosheet_rev1.pdf

 

[manisandher]

"Mani, could you start another thread about that, or send matan a personal message? Let's keep this thread on-topic."

 

So, all the earlier talk of ethernet DACs was on-topic, hey? Hmmm...

 

In any event, I'm hoping to compare my C.A.P.S. (with linear PS!) with my two underclocked/undervoltaged i7/TNN300 and E8600/TNN300 machines and at some point. Will report back... and try to remain on-topic :-)

 

Mani.

 

[Audio_ELF]

@ziggyzack...

 

Yes, I know perfectly well about the Linn Klimax DS: however I don't consider it meets your criteria / description as (I believe) you were talking about a device which is sent SPDIF type, format independent, data rather than computer files (such as WAV, FLAC, etc).

 

UPnP devices are sent data as WAV / FLAC / AIFF / AAC etc and need to be able to decode this before playing.

 

Maybe I have understood you wrongly - my thought was that a computer device would convert an Audio file to data before sending it to the DAC - like a computer converts a Word file to rasterised or page description data for it to be transmitted to a printer.

 

Eloise

 

[ziggyzack]

Maybe I have understood you wrongly - my thought was that a computer device would convert an Audio file to data before sending it to the DAC - like a computer converts a Word file to rasterised or page description data for it to be transmitted to a printer.

 

Ah! Yes, that's not what I meant at all! I did have a brief pop at saying this in my earlier rant to Chris: 'with ethernet, the data is delivered asynchronously [with emphasis this time], so the buffer output and dac are timed by the same, local, clock'. But I can see that saying things like 'music data arrives via the ethernet port' wasn't very well put - I pitched that poorly.

 

The Wolfson dac chips in the Klimax accept either PCM or DSD inputs, but no, I certainly didn't mean to suggest that the decoding should be done on the computer, and that a clocked stream of PCM or DSD were transmitted to the dac via ethernet. Ethernet is not the right medium for such a stream at all. Furthermore, transmitting a synchronous signal wouldn't overcome the clocking issue inherent in spdif.

 

I absolutely do mean that the computer should stream flac, wav, alac, aiff, and that the 'ethernet dac' should decode the stream locally. This gives the great advantage that the pcm being pulled from the audio buffer is run by the same, local, clock as that running the dac chip, so the issue of interface-induced jitter is rendered moot. Music goes into the buffer asynchronously, and comes out of the buffer timed identically to the dac chip.

 

Of course, this means there still needs to be decoding done inside the same box as the dac, but I don't see that as an issue. Decoding is lightweight - tiny portable mp3 players can do it. Audio codecs are designed such that the encoding step is more work intensive than the decode (so an mp3player has no trouble decoding an mp3 file in realtime, but wouldn't manage encoding in realtime. This is for power efficiency in playback too. So yes, an 'ethernet dac' still needs some processing power for control logic and decoding, but that is a far cry from the kind of power needed by a computer. It's much more akin to what goes on inside a CD player.

 

Finally, UPnP (or UPnP AV, more specifically) is a good, open standard for control, but what I'm describing doesn't necessarily have to be controlled by UPnP. But if it were, you could have UPnP audio rendering software on a computer in a study, a Klimax DS in a listening room, a cheaper hardware UPnP-compatible renderer in a kids room, and control them all from the same software from wherever you are in the house, or from outside if you like! It's an awesome idea.

 

ZZ

 

[Audio_ELF]

@ziggyzack...

 

Okay so I now understand what you are talking about, but at the end of the day, there is little difference between the computing power needed to run the software in a Klimax DS, and the power needed to run mPD on Linux.

 

I'm not saying that makes the Klimax DS an irrelevant option, but it's just that ... an option. Not really better or worse than a UPnP streamer system. Also a UPnP device is usually dedicated to one device and can't be customised. That is both a blessing and a curse.

 

Eloise

 

[ziggyzack]

I don't disagree. Having glanced very quickly at the MPD website (I know nothing about it), I presume you mean you'd continue to have the client and server duties split, but I haven't seen how they communicate. But then it comes down to the hardware choices and design on the client. What processor? What power supply, dac chip(s), permanent memory, output stage? How do you arrange them and power them to maintain separation of the digital and analogue stages? Design and implement that well, and you could have yourself a very nice player. Perhaps you could sell it.

 

We're a far cry from the OP's original question though: 'For example, I've found that using my dual-core CPU in single-core mode sounds noticeably better. Could that be due to the lower power consumption?'

 

Bit OT, but would you embellish on 'Not really better or worse than a UPnP streamer system. Also a UPnP device is usually dedicated to one device and can't be customised. That is both a blessing and a curse.' I don't follow.

 

Thanks,

ZZ

 

p.s. when I said earlier that I'd pitched my explanation poorly, I meant too low! Apologies for any misunderstanding.

 

[Audio_ELF]

ziggyzack asked... "Bit OT, but would you embellish on 'Not really better or worse than a UPnP streamer system. Also a UPnP device is usually dedicated to one device and can't be customised. That is both a blessing and a curse.' I don't follow."

 

Well with a computer based solution (be it Mac, Windows or Linux) you have the ability to play back videos, utilise Spotify and countless other sources of audio and video. While this is outside the bounds of a "music server" they are part of the whole package (to me). Many of these don't work on UPnP (or other streaming systems) such as Linn DS.

 

Now you can also use the argument that it's the very ability to do these extra tasks that makes a general purpose computer bad for computer audio.

 

Hence a blessing (to be able to do the tasks) and a curse (they distract from the music system).

 

Eloise

 

[ziggyzack]

At what point did I say a computer wasn't necessary? right at the start, I said 'With an ethernet dac, the server can be a NAS or computer tucked away in a study, under the stairs, or installed in a loft, to give three possibilities. I.e. anywhere but the living room or music room.'

 

UPnP AV distinguishes between 1) renderers (players), 2) control points and 3) servers. You can have an UPnP-compliant DAC as a randerer (and UPnP is designed for ethernet networks, so that explicitly means an ethernet dac), but if you have no UPnP server, then you would have no music. Clearly a computer is still required - the point is that all it does is serve the music, like any other file, and it is left up to the renderer to be a dedicated and optimised audio player.

 

UPnP control points are by definition customisable. UPnP defines many aspects of how UPnP devices should play together, but it doesn't define your media sources. UPnP control points often allow drag and drop of any audio source (including internet radio, spotify, last.fm, etc.) It's up to the control point designer if he wants to present the interface as a radio tuner, for example, perhaps sourcing stations from a radio hub like radiotime, or using some other UI paradigm. There's a UPnP plug-in for foobar. MediaMonkey say they will introduce it in V4. There's a vlc plug-in which lets you synchronise video playback through vlc while serving the audio via UPnP.

 

Ideally, in the vlc case, the video would be streamed to a dedicated video renderer (no moving parts, no hard disk, just an ethernet in, video decode electronics and hdmi output - although in the case of video this should really be integrated into the TV) and the audio sent to a dedicated audio renderer, although I think there would be difficulty synchronising - possibly an improvement to the UPnP AV spec needed there. Anyway, the principal is: minimal complexity in the renderers, especially audio renderers because oof the analogue nature of their output. As much complexity as you like on the server (library management, serving several renderers at the same time, backup regimes, ability also to run Excel, etc.) and control points that run elegant control software on convenient living room devices (ipads, other ithings, other smartphones, tablets, netbooks, your watch, etc.)

 

Hence a blessing (to be able to do the tasks) and a curse (they distract from the music system)

 

On the contrary, have the best of both worlds!

 

[Audio_ELF]

ZiggyZack ... you are right ... back at the start you did say that a computer (or NAS) is still needed but your fundermental argument is about getting the computer out of the listening room. However this is not necessary (IMO). A MacMini is off the shelf virtually silent, more so if you swap in a SSD. An Atom based PC has sufficient processing power for music (and with the right chip-set HD video) and can be run without fans in the correct case. This gets rid of most of the reasons for avoiding PC in the listening room in one fell swoop.

 

You are also correct that you can run video over UPnP. But (with all due respect) everything you comment on increases the complexity compared with simple Mac or Windows computer as a music server without providing any increased sound quality.

 

At the end of the day there is a place for all these devices in different systems and (so far) non have proven to be superior (even theoretically) over any other. I'm keeping my mind open to all options.

 

I do acknowledge that if you could split audio and video, a system where there was a video UPnP renderer in the TV, and an audio one as part of your DAC would be interesting ... so long as you can keep them in sync!!

 

Eloise

 

[Guest Claude]

Back to the main Topic.

Does anyone know, how to underclock the cpu on a mac? Does underclocking of an cpu also reduce power consumption? If not, is it possible to reduce powerconsumption on a mac (mini not laptop)? I would very much like to experiment with that, because I already know, how much difference it makes to change priority of processes and getting rid of unnecessary processes. On this there are various threads, but I couldnt find any on underclocking.

 

All the best from Germany

Claudius

 

[ziggyzack]

The look like very nice pieces of kit to me. Atom based PCs also - and the range of processors is growing and improving. Definitely have their place, it's just that I think you can do better if you're heading towards high-end, or have more than a single listening/viewing room.

 

You can deal with the audible noise coming from a mac/pc, but also need to address the power supply. We're replacing hard disks, looking for quiet or fanless computers, worrying about power pollution. I wouldn't say your way is necessarily easier (ok, I haven't tried syncing up video and sound, but you can just stream to a combined AV player for movies).

 

An ethernet/upnp dac has a better theoretical design than a dac using spdif. Async USB and firewire I know less about - but they seem to be trying to emulate what ethernet was built for, and don't have the wider control options.

 

If you want to listen to music in two rooms in your house, well, no contest (and with no compromise SQ). I think there's little in the way of contest even if you have a single listening room, but once you've set yourself up in one room, all you need to add another is an ethernet connection and another ethernet dac. Done.

 

Open mind is cool with me - I am not a UPnP salesman, just wanting the best for myself and others!

 

[Audio_ELF]

An Ethernet/UPnP DAC has a better theoretical design than a dac using SPDIF. Async USB and FireWire I know less about - but they seem to be trying to emulate what Ethernet was built for, and don't have the wider control options.

 

One of the original criteria of FireWire was for the real time transfer of digital audio from ADC to Computer and back to DACs. Nothing is "trying to emulate what Ethernet was built for" - UPnP works in a completely different manner from SPDIF / Async USB / FireWire connections. Infact is anything was "designed for audio" it would be FireWire where one of its original design briefs was to provide interface between DAC/ADC and a computer. Anyway they are pretty much all not better, not worse, just different and presenting different problems and issues.

 

If you want to listen to music in two rooms in your house, well, no contest (and with no compromise SQ). I think there's little in the way of contest even if you have a single listening room, but once you've set yourself up in one room, all you need to add another is an Ethernet connection and another Ethernet DAC. Done.

 

I do agree with you the UPnP is great (when working well) for a multi-room system. But I would think very few people are actually worried abut such high quality audio in multiple rooms. I do really wish you would stop calling it an Ethernet DAC as it's not, it's a UPnP renderer or simply an Ethernet streamer. In many cases people are connecting a UPnP streamer (such as the lower end Linn DS devices) to a secondary DAC via SPDIF.

 

At the end of the day, most pieces of kit have their advantages and places they are limited. If you take a brief look at the Naim forum, many people have given up trying to get their NaimUnity to stream audio as UPnP is temperamental. On the other hand SPDIF while technically inferior to USB has been shown to work well by Chord and Naim both of who implement various forms of FIFO buffer to counteract jitter. Gordon at Wavelength builds brilliant USB interfaces to his DACs.

 

All of this is, as we say, completely off the topic of "Low power or high power computers for best SQ?"