AES/EBU vs HDMI Digital Outputs


#1

Has anyone ever compared the SQ of AES/EBU output on the DMP to the i2s (both going into the DSD) using the same brand of cable? I have an opportunity to buy a Wireworld Platinum Starlight 7 at a decent price but its an AES/EBU cable. I never see i2s versions of the same come up second hand. I would imagine they are both high quality cables. I just wondered how much sound quality I’ll lose (if any) using the AES/EBU instead of i2s.

Thanks.


#2

Can’t answer that question but you would lose the ability to play the DSD layer off of SACDs. That only works over I2S.


#3

Thanks. Reason enough not to go down that road. :grinning:


#4

If you are dealing with digital signals on electrically sound cables the conductive medium should have no effect whatsoever on sound quality.

The signals on those cables are square waves --serial data, to be exact-- not analog audio. As long as all the bits reach the other end, the resulting sound quality will depend entirely on the quality of your source and DAC.

This is the big advantage of digital signalling… absolute fidelity. It works like this… To send a 1 bit the sending device sets the voltage on the wire to be greater than 1 volt. On the receiving end any voltage greater than 1 volt is considered to be a 1 bit. For a 0 the same logic applies except that the voltage has to be less than .6 volts. Nothing else matters except 0 or 1.

Even jitter (bits that are transferred early or late) is compensated for in the receiving device by using a very narrow sampling window centred in the intended width of a bit. The bit can be early or late by up to 25% of it’s width and you will still get perfect data transfers.

So don’t fret over two different types of digital cables … HDMI is not better than USB or Optical … all are digital methods and all will transfer data with 100% fidelity.

That the one cable you were considering won’t work with one or more digital methods is, as you observed, a much better cause for your decision making.


What do you think about this AC-10?
#5

Perhaps counter-intuitively, data cables can make s difference. While any decent cable will transmit a bit perfect signal, how they carry this signal can impact the amount of jitter in the signal. Jitter is simply a deviation in the edge signal from its proper point in time. Cables can have an impact on this timing how fast the signal’s edges are, etc. Proper grounding, immunity to outside interference and the like can also have an impact.

It is annoying. I do not like that interconnects and speaker cable sound different. I like even less that digital cables can sound different.


#6

It’s wire. Just plain old passive copper wire. The signal is digital … the cable cannot change the signal, alter it’s timing or contribute anything to the signal. Whatever goes in one end is exactly what comes out the other… and since it is all digital nothing matters except the 2 voltages I described in my initial comment. 1 or 0 … nothing else matters.

The only exception to that would be if you were in an area with strong radio signals as would be from a transmitter or heavy industrial equipment. These signals could invade the cable and cause bit errors… but even then a bit error here and there would also not have a profound effect on sound quality.

Trust me on this one … if a digital cable can send a file to (for example) an external hard disk without errors… it can send it to a DAC without errors. It’s all the same signals … 1 and 0. If you are hearing differences in sound quality, it is coming from someplace other than your digital cables.

Now, your RCA cords and speaker wires are analog signalling… and that’s a whole different story.


#7

And don’t forget that how the cable is built (coax, twisted pair, unshielded, shielded with shield connected only on one end, shielded with shield connected on both ends, balanced vs unbalanced,…) will affect your system even assuming (wrongly) that the quality of bits makes no difference if there are no errors. Non-optical cables all add an opportunity for more groundloops, and these groundloops can affect any component of the system, especially by adding noise to analog signals, etc. Cables also possibly receive RFI, but they also emit RFI which can affect any other groundloops and other analog connections in the system (or even the components in the system.) The thing about digital signals is the squarer they are the more they radiate and the more high frequency crap they have…

One of the first things we were taught in engineering school was to pick our models carefully, drawing conclusions from a model that’s too simple is the biggest thing to avoid. If the model is too complex it only causes more work. Finding the right models is what it’s all about. Cables are more than LRC. Digital is more than bits (e.g. the timing of the bits makes a difference exactly when and where the bits are changed to analog (e.g. where there is no clock downstream). Putting bits in a buffer and using a PLL to generate the clock to take them out only low pass filters the jitter and it’s the low frequency jitter that matters most in audio so a PLL that tracks accurately enough to allow small buffers allows more jitter thru… TANSTAAFL.) And don’t forget that every time a bit is checked for being high or low any noise on the ground or power supply is injected as jitter and conversely the incoming jitter causes switching a little early or late which changes the time the power supply is used thereby converting some jitter to analog noise. These things do matter and are easy to see on a scope.


#8

Your analysis is correct only if you are discussing edge triggered logic with no downstream clock… There jitter can be transferred to the DAC input… but it will not be the fault of the cable, it will be a problem in the digital sender.

But, except for really crappy design, nobody does that anymore. Instead they use windowing… a very short and fast sample taken at the centre of the time frame in which the bit is to be present then latched into a buffer that operates from the local clock. By using a narrow sample window a bit can be too wide, too narrow, early or late and the receiver will still get the correct information.

Ground loops can be an issue but there’s no way a cheap cord can cause that and no way an expensive one can fix it… it is a flaw in the design of the system itself and it most likely has nothing to do with the data cable.

Let me give you a real world example of just how little difference it makes … A friend of mine got the bright idea that his USB cable was causing a loss of treble in his system. So he goes out and comes back with a $70.00 2 metre USB cord. So I gets behind his racks and hooks things up. He was immediately thrilled at how much better his system sounded. I didn’t have the heart or the courage to tell him that I’d put the original $6.00 cable back in.

Seriously … anyone who experiences audible differences with digital cables is either fooling themselves or has other problems in their system.

Bottom line … it’ just a chunk of wire.


#9

Seriously wrong… Yes there are cables that are expensive and don’t work as well as cheaper ones in some (sometimes many) systems. But I’ve done A/B tests many times on friends and family that show cables make an audio quality difference (and for that matter double blind tests on myself). Everything I wrote about in my previous post isn’t just theoretical, they are measured easily on a (good) scope and, yes, I do this for a living. Don’t extrapolate your limited experience to everyone and everyone’s system. Real science starts when you observe something different than you expect, then you can make progress. Just assuming your models of the world are correct blinds you to the real (and interesting) complexities of the real world. (I know that never assuming anything keeps you from making progress too, but looking at things that you can measure is a good start.)

Don’t get me wrong, there’s a lot of non-grounded speculation (and some outright hucksterism) out there and a lot of over credulous people which may waste time or money chasing the perfect sound. But listening for yourself vs. blindly listening to people on the net (pro or con) is the way to go.


#10

A wonderfully balanced summary, Ted.

Keep an open mind, but not so open your brains fall out.


#11

Now comes the part where you need to stop making assumptions… I have more than 30 years professional experience in electronics including audio and computers… even a short stay in 2 way radio. This by the way includes about 8 years of design level experience with microprocessors and peripherals.

I don’t cast doubt on your experience or accuse you of a lack of knowledge and I will thank you to not do that to me. Just because I’m new to you does not mean I am new to THIS.


#12

Back at you. I presumed your experience based on your apparent lack of knowledge about what things make practical differences in audio.

Just for example :

Cables affect jitter in many ways including their bandwidth, their characteristic impedance (length, etc.) that affect the timing and shape of the signals… Ignoring the DAC part of the equation, the jitter and noise interact anywhere in a digital circuit even if you only care about the levels when they are clean. There’s no issue with getting the correct bits, but the timing is another thing.

The edges of the incoming data are almost always used to control a PLL or FLL and you skipped right over the fact that PLLs and FLL’s are only a low pass jitter filter. The clock that you generate for the PLL (or something derived from it) is almost always the same clock that the DAC proper uses and at that point the jitter that came very directly from the incoming edges directly affects the resultant audio. (and there are many measurable secondary effects caused by the noise/jitter all over the DACs’s hardware, power supplies, etc. (We can discus how ASRC doesn’t really fix things either.)

Whether a cable is balanced or not (along with the topologies of the transmitter and receiver) definitely does affect the amount of noise injected in it (or the transmitter or receiver) by a ground loop. The style and quality of the construction, shielding, etc. affects how much common noise cancelation there is in a balanced cable. The quality of the grounds and shielding of the cable affect how much the ground loop current affects the data (or analog) signal by conducting more or less of the groundloop current between component’s grounds vs. the remaining groundloop current in the data/signal lines.

The thing to bear in mind is that many of us clearly hear things down 78, 84, 90dB from FS. (There are many studies about whether 16 bits is enough compared to more, but no one really thinks 13, 14, or 15 bits is.) The ear has the most dynamic range of our senses and is very sensitive (in the right circumstances) to small effects on the order of the things I’m talking about.


#13

It’s been fun talking with you … have a nice day.


#14

Trying to bully is not nearly as much fun when someone bigger than you comes along, is it? :grinning:


#15

Elk, You’re a pisser. (Is it ok to say pisser here?)


#16

It appears to be OK. :slight_smile:

I call them as I see them.

We have had many engineers, and other self-proclaimed experts, use the rhetorical tool of claimed superior qualification intimidation to attempt to force others to accept what they are saying. I, for one, am never impressed.


#17

Geez, I just asked what I THOUGHT was an innocent question.

I know digital cables can sound different because I’ve experimented with nearly a dozen of them. Ted is right, there is not necessarily a correlation between cost and SQ. The cable I liked best was AQ Vodka so I bought the more expensive AQ Coffee. I can’t tell you why, but the Vodka was better as an i2s between DMP and DSD. Conversely, Coffee produced a much better video picture than did Vodka on my 4K TV.

I have given up guessing and just try new ones from time to time.


#18

I’m lucky in that there are members of the local audio club that will let you borrow cables for a week or so (and some have some very expensive cables.) Often it’s when you put the older cable back that it’s obvious which one works best for you in your system. There’s also https://www.thecableco.com/lending-library

Fortunately (or unfortunately depending on how you look at it) at this point I have multiple extra cables which I try on each new piece of equipment to see which works better in my system at that time.


#19

All the money and science in the world and we don’t know how aspirin works or if coffee is good for you or not. We have a long way to go…


#20

For me it’s absolute. When I go backwards is when I really hear the difference.