paulb

and ones after, but not that particular one. Very odd. In any case, it isn't particularly relevant to the discussion, just a bit misleading to others of my intent.

I should have put a smiley :-), but I note that I am locked out of going back and doing that. Strange, the only one of my comments that has been locked and the only one where I have written something questionable. Must be one of those wifi errors I read about :-) However, didn't mythbusters try it with with a few hundred phones, which is what you'd need in theory. The problem is that the output is not coherent nor continuous and it's hard to get all the phones running at once, so pretty impossible to achieve. So it's technically possible, but in reality, not a chance. Someone tried to claim for a tumour from using his phone, but it turned out that he was an engineer that had it strapped to his head with an elastic band and the early phones did put out a lot more energy. PS, you can get the phones to push out a lot more power in low signal conditions, about 2W each. So whilst the viral was a myth, I can see why people believe it.

They are all data packets as far as the protocol is concerned, although you can treat audio and video data as time bounded so that it gets priority over other data packets, since you want to ensure that it all gets there in time and you don't get drop outs. Streaming audio is only on transports like SPDIF, not WiFi. WiFi also has additional features for maintained data integrity that ethernet doesn't have, CRC checksum and packet fragmentation, so it actually has better checks for corrupted data. Here's an explanation that puts it better than I could: "Each packet has a CRC checksum calculated and attached to ensure that the data was not corrupted in transit. This is different from Ethernet, where higher-level protocols such as TCP handle error checking. Packet fragmentation allows large packets to be broken into smaller units when sent over the air, which is useful in very congested environments or when interference is a factor, since larger packets have a better chance of being corrupted. This technique reduces the need for retransmission in many cases and thus improves overall wireless network performance. The MAC layer is responsible for reassembling fragments received, rendering the process transparent to higher level protocols." So the reality is that whether it is ethernet, or indeed WiFi, unless you get a break in transmission, you get the exact data at the end that was sent. There is no corruption within packets causing subtle effects and only major drops which are very, very audible. I think the point that was trying to be made was that WiFi can cause RF interference, but again they operate at a tiny fraction of the power of microwave ovens and audio gear has more than adequate filtering. Wiring might pick it up, but the frequencies are in the gigahertz, so completly and utterly inaudible. I wish more time was spent discussing real hardware improvements that are possible, rather than poorly-understood rumours. Much can be done through excellent engineering, high quality components and careful design. Most, if not all, of the shortcoming in our equipment are down to cost.

There have been FM radio transmissions and local taxi firms squirting out RF mush into the environment for years and hifi manufacturers encase their electronics and suppress it well. I guess if your gear isn't that well constructed then this crap might affect it, but WiFi is up in the gigahertz, doesn't travel far and nowhere near audio frequencies, so easily filtered out. And whilst Wifi does operate at the same frequency as microwave ovens and can get messed up when you are reheating your pot-noodles, the power output from a wifi router is minuscule by comparison (0.1W as opposed to 800W). All other equipment that unintentionally transmits radio interference is limited by law to around 0.1 microwatt, I seem to remember. So whilst you could claim it is a microwave oven, it is like standing in cold water rather than a scalding bath. It ain't ever going to hurt. I happen to work in the mobile industry and there has been tons of research done into power output of phones. Manufacturers are acutely aware of health concerns and handsets subjected to far more testing that you would imagine. Yes, it is true that you can cook popcorn with a few phones on a call at the same time in a low reception area (so the amps are up at full wick), but when they are idle, the RF amps are in a quiescent state and putting out very, very little energy (otherwise your battery would only last a few hours). So, you may have a point if you are making a call near your stereo if it has poor noise suppression, but 99% of the time, the phone isn't doing a hell of a lot. The one inescapable thing about ethernet is that it is pretty much immune to interference and so drop-outs, so if you can, use it.

It's your web site and you can choose what goes on it, but I thought this was a reasoned debate, unless of course that isn't allowed?

Use ethernet for data transmission. Turn on Wifi, listen, then power it off and listen again. Does it sound better? The problem for me is that you excuse yourself by saying you can't explain it, but state it as if it an absolute truth. Then offer up some hopeless pseudo science as a possible reason why. Polling on the WiFi won't affect the digital output. They are different circuits operating at different frequencies. My Squeezebox has WiFI and ethernet. Both sound exactly the same. My MacBook Pro has ethernet and wifi. Sounds exactly the same through both. SlimDevices have even measured it accurately. It is the same.

It cannot change the audio. It either works or it doesn't. There is no mechanism in the transmission that changes the data and all that there is is the data. It's not like SPDIF where there is jitter, within a LAN it is packets of data transmitted in sequence and in an accurate manner. The only exception to this is when packets don't arrive, but then you have gross distortion. There are no subtle effects, like "improved bass", it's perfect transmission or big holes. If you believe that WiFi affects the sound, then you can't just say it, you have to prove it because all the evidence is against you. I can prove it doesn't affect the data and the sound, because you can read this posting. The data was transmitted perfectly from my laptop to the router. Your stance also really does audiophiles no service, because it tries to imply that hardware manufacturers don't understand coherent and reliable data transmission, which is clearly not the case or none of our devices would work. Data transmission over LAN, whether wired or unwired, within computers, and over different types of protocols and hardware, is extremely well understood. For example, you are probably reading this on a PC running at several gigahertz, so running electronics at way higher frequencies than audio data, yet it passes information around thousands of millions of times a second with total reliably. Not to mention that we can build massive scientific instruments like the Large Hadron Collider and measure within atoms, all with data transmitting at way higher rates than audio and total accuracy. You wouldn't question any of that would you? All wifi does is pass data between devices. It neither adds nor subtracts or it wouldn't work at all.

Just to be clear on the setup, both were feeding the same DAC through optical connections using the same cable?<br /> <br /> If that's the case, then the only device related possibility left is jitter as there is no electrical connection and the data is exactly the same. <br /> <br /> The other aspect to consider might be volume, or application of a volume function when using one or other of the outputs. <br /> <br /> There can be no difference between a wired or unwired data connection, otherwise I couldn't write this message for example. My guess is that the data going into one or other has had a volume adjustment made on it.<br /> <br /> Paul

Hi Chris,<br /> <br /> You mention that you found the Lynx card to sound better, presumably both were playing via their digital outputs, in which case do you put the difference down to jitter as both should be in theory bit perfect?<br /> <br /> I wouldn't be at all surprised if the Airport Express was worse at analogue, it must have a fairly crappy PSU, but when used as a digital transport, I would expect the performance to be pretty good when connected to a decent DAC. The only reason I can think of that it wouldn't be would be a poor jitter performance as it is an optical link.<br /> <br /> I was thinking of getting another one for my set-up, my LogiTech Duet is now gathering dust as its user experience pales beside Apple Remote on an iPod Touch. Just too slow and clunky by comparison. I'm currently goin direct from a MacBook Pro digital out to a MF XDAC3/XPSU3 (The additional PSU makes a big difference)<br /> <br /> Paul

but I think what you are describing is replacing less than bit perfect playback mechanisms with your own one. That's not snake oil and what you have built is a transparent playback engine. Great stuff. Of course, if what you are saying is that it was bit-perfect before your player was built, and still bit-perfect afterwards using your player (e.g. you looked at the data coming out of the digital out) and all other parameters such as jitter, noise etc were consistent, but it sounded different, then I would suggest that one or other of those statements isn't true, or you have made a change and just haven't realised what it is yet. Computers are very noisy environments, so processing something in a different way might change noise on the signal coming out, but DACs are used to handling that kind of garbage. I am interested to hear what you think you have actually done to improve the sound - what was driving your coding design?

My point about the comparison was that you can easily validate that the data received is the same as the data sent. If it weren't wireless networks wouldn't work. A file goes in one end and comes out the same the other. The text I'm writing will be the same when it appears on server that creates this page. What you describe isn't the same as I was saying, you can hear the difference caused by a measurable phenomenon, jitter. I'm talking about reviewers who swear that they can tell the difference between a lossless file and a WAV file when they are decoded by the player, or when the player uses WiFi instead of wired connections. The data *is* the same. The output from the player is the same, it's using the same internal hardware to decode the same data, likely from the same buffer. So in your case, the comparison would be using the AppleTV to play back music from another Mac library first using wireless connections to the music server, and then wired. One will be more reliable than the other, but better sounding - that simply does not make sense. Unless the gear was so badly designed that power supplies drooped or interference was not suppressed adequately, the incoming data when decoded is the same and it goes through the same DAC.

I have correct this misnomer of scientific theory - and sorry if I am late to the discussion and taking it back to an area that has been covered already, but I would like to add my 2c. And this is not meant to offend any faith, faith is not science, and I'm discussing science. In scientific terms, evolution is a fact, demonstrated by masses of evidence such as fossil records, e.g. the visible changes in bone structure of reptile jaws as they become ear bones in mammals, or more recent evidence such as the changes seen in butterfly colouration during the English industrial revolution. Argue why it happens if you must, but it happens. We can even make it happen ourselves through selective breeding. Are there gaps in the fossil records? In fact they are pretty complete, but even if there were gaps, not having 100% history of the world wouldn't make the rest of the evidence invalid. So far we have Darwin's theory of why evolution happens, it has evidence supporting it and it has undergone peer review. It seems to be a good explanation. It may be wrong and there may be aliens tweaking species from time to time when we aren't looking, but so far no one has found any evidence for that. If you really want to argue against Darwin, some evidence to support an alternative would be a good starting point and believe me, scientists love nothing more than disruptive evidence that rocks the boat and means the beginning of a whole new line of research. It's why they build things like the LHC. To be precise, a scientific theory is an explanation of fact. Theories may change, as with subjects like Newton's laws which don't work at subatomic levels, or more recent theories like Einstein's that have made way for string theory for quantum physics and cosmology. Theories may develop, but the facts or process they are explaining do not alter, even if they may be better understood or measured. Nor does that make a scientific theory a best guess, it requires peer review and evidence. It's this lack of understanding of the rigor of scientific theory that fuels so many heated discussions. They aren't just ideas, they have to be carefully considered concepts backed by solid evidence to pass muster. This applies all science, not just those areas where faith gets involved. We are discussing audio technology here, based on theories of solid state physics, and the way in which quantum physics works is still not understood entirely, but we accept the facts we do know of electronics, and without it we'd have no computers, or stereos and no internet to be discussing this. We don't dispute our doctor's advice because not all of human biology is understood, nor do we refuse to get in a plane when we know that aeronautical theory doesn't have all the answers. We trust those scientists, so why have some regard for all scientists who follow the same rigor and peer review? But to get back to audio, I personally got tired of audiophiles and the magazines ignoring evidence and science when it came to reviewing technology and easily measurable effects. They would conjure up romantic and flowery language to disguise their lack of process and rigor and an unnerving desire to recommend based on price tag. More than that, they started making pseudo-scientific judgments on aspects of hardware, such as hearing data loss in digital networks, where clearly such an event would be catastrophic for computers in general. When you read that WiFi is sonically inferior to wired cables, or lossless formats sound worse than WAV, you know a wheel has come off the audio bandwagon. Having spent thousands in gear. I eventually settled on mid-fi and digital reproduction via first a squeezebox and then a macbook and just started enjoying the music. It's very easy to lose sight of that, recorded music is never true fidelity, but a studio artifact, so chasing the dream of ultimate reproduction is simply trying to recreate an artiface that never existed outside of a soundproofed room. Today's gear is more than adequate at reproducing popular music in high enough fidelity for most of our aging ears. I might have been able to tell the difference between esoteric brands of high end gear years ago, I know I can't now, so I won't try to fool myself.