HI FI INTERCONNECT CABLE DIFFERENCES

[djoptix]

Put that in context of the cable inside your PC, betwixt hard drive and mother board / controller.

Then tell me there's sense in spending lots of money on digital cables.

That's a special case - the cables are incredibly short and hence have hardly any capacitance to speak of, and don't have to reject interference, so they can be cheap and small.

Look at the type of cable that's used for networking.

IT doesn't have the budget (typically, these days) for spending on expensive, overpriced cables, and the same types of 0s and 1s at easily the same speeds (probably much, much, more).

Cat5 can be used for very long runs because of its balanced pairs which have a very tight and controlled twist. This makes it excellent at rejecting interference but it's not ideal for audio because it's flimsy, would suffer from handling noise and it's difficult to terminate into audio connectors. Plus once you're transmitting a lot of audio you have to start paying attention to curve radii when installing which is tedious. Nevertheless you're right that it does do a very good job of transmitting a digital audio signal like SPDIF or AES. There's masses of error correction and redundancy built into network equipment so traffic still flows well over cat5 despite the errors. The difference for audio traffic is that you have a finite amount of time to do error correction and reconstruct the signal because it needs to make it out of the speakers by a certain time, which is why digital cable has to be properly specified, terminated and shielded. For instance, I've just pinged my router which is being a bit temperamental. Usually it takes under 2ms for a response but sometimes it spikes up to around 20ms. In the context of network traffic this is completely unnoticeable but in an audio context a sudden 20ms delay of the data getting through would be disastrous. Of course the cable hasn't actually introduced a delay, it's just that the error correction has taken this long to spit out meaningful values of a signal which has been compromised.

Shamelessly borrowing from a recent Sound On Sound article:

This shows the result of sending an AES3 signal through 2m of Canford Audio’s DFT digital audio cable. What this graph is showing is a series of sections of digital audio data, all overlaid over one another. The top, horizontal blue line represents the high data value (binary 1), and the lower blue line represents the low data value (binary 0). Individual data bits obviously exist only at one of these two levels, and the divisions between one data bit and the next are represented by the vertical blue lines.
As you can see, with this digital audio cable the source signal is being received still looking very square and clean, and each individual ‘bit cell’ (also referred to as the ‘eye’ pattern) is clearly identifiable and very ‘open.’ The small red rectangles within each bit cell represents the minimum eye pattern area that must be kept clear for the receiver to be able to interpret the data reliably — in effect, this is the ‘decision zone’, where the receiver has to decide whether the data is high or low for that specific data bit.

The second graph shows exactly the same thing, but this time with the signal passing through 2m of standard professional star-quad microphone cable. The rising and falling edges between each bit cell have obviously been slowed down dramatically, and follow a ragged curve rather than the crisp up or down switching seen in the DFT cable. This is due entirely to the capacitance of the cable storing, and then releasing over time, the electrical energy from each change of signal voltage. While the damage is very obvious, it’s still not disastrous and the data can still be received reliably — but you can certainly see how the eye pattern is starting to ‘close up’. Now imagine what would happen if you tried to send a signal down many tens of metres of mic cable! In practice, it would become unrecoverable after about 15 to 25m.

The critical aspect of this waveform damage is that the rising and falling edges of each bit cell are used to define the bit-clock transitions, and the distortions caused by cable capacitance can therefore introduce clock jitter.

With S/PDIF and AES formats, clock jitter is directly affected by the audio data content to some degree, because of the different cable-capacitance charging and discharging times that occur.

The diagram above shows how the data is conveyed in the S/PDIF and AES3 interface formats. The audio data ones are conveyed by switching the signal between high and low (or vice versa) mid-way through the bit period (ie. sending the 3MHz square wave), while audio data zeros are conveyed by remaining at a constant level for the entire bit period (sending the 1.5MHz square wave). This arrangement is actually very similar to the way standard linear timecode works — although that system operates by switching between 1kHz and 2kHz signals, giving rise to the characteristic warble. This kind of channel code arrangement (often called a Bi-Phase Mark Code) has the advantage that the recovered data is not affected by the overall signal polarity — all that matters is whether the signal transitions midway through a bit cell period or not, rather than whether it is a high or low voltage at any particularly time. However, as the diagram shows, the amount of clock jitter is directly affected by the audio data content to some degree, because of the different cable-capacitance charging and discharging times that occur.

Ideally, the receiving circuitry will be able to remove this interface jitter, but not all devices manage this equally well (as shown in the investigations into A-D converter clock-recovery above), and if the embedded clocks are to be used as a clock reference (as is common practice in D-A converters, for example), then this interface jitter can become part of the overall system’s clock jitter, potentially resulting in reduced D-A (or A-D) performance.

----------

Despite my rant I wasn't saying that spending huge amounts of cash on digital interconnects is justified. My point (as drcarlos has said) is that if your cable meets the right standards for digital audio transmission, it will deliver identical results to a special, super-shielded, hand-welded-by-virgins Monster cable costing £1000 a foot. But you do have to get the specification right in the first place. Nevertheless (Neil) you are right about Cat5. It is used to transmit massive amounts of audio data over large distances with great success such as in the up-and-coming Dante protocol. (http://en.wikipedia.org/wiki/Dante_(networking)) However, even Dante struggles when using standard network interfaces to pass audio and works much better with its own kit.

Line level audio is much more tolerant of cable differences and IMHO your interconnects make little difference as long as they don't have too much capacitance and are well-terminated.

Speaker cable even more so and as long as it doesn't exceed 5% of the rated impedance of the system, makes no discernible difference.

 

[greenstiles]

CYFA hi fi interconnect are phono cables between your CD player / tape deck / etc and your home amplifier..

 

[greenstiles]

I haveto say though that some interconnect DO require burn in, and sound quite different then ...why i don't know ! while others sound the same from oot the box to fully burnt ?????..........

I think the bottom line is this..... everyone has different shaped ears and different degrees of hearing- like eye sight :shock: BUT added to the equation are a huge amount of placebo cables that do nothing !........but the are a few out they that do make a difference. Not many though, and it's nothing to do with price either...........the black art continues :twisted:

 

[greenstiles]

interestingly.........' What HiFi' the much respected mag and now website, refused to accept the opinions of many many people about how good the Swiss Gotham GAC 1 cable was off ebay ( £17.00ish) compared to very very expensive cables they like....they just would not have it and finally reviewed it very badly indeed saying they couldn't understand why everyone raved about them................how could all those people be wrong, quite a few even sold off their expensive cables and replaced them with the above cheap ones !!! :shock: usedon very expensive kit.......................is it money in back pockets / freebies for the magazines ? from HI Fi companies to continue quaffing how good the famous companies stuff is ????..............i know those cables are better than lots of others too

 

[JohnH]

Cat5 can be used for very long runs because of its balanced pairs which have a very tight and controlled twist....

Thanks for the post, djoptix. That was a very interesting read!

 

[Neil]

Put that in context of the cable inside your PC, betwixt hard drive and mother board / controller.

Then tell me there's sense in spending lots of money on digital cables.

That's a special case - the cables are incredibly short and hence have hardly any capacitance to speak of, and don't have to reject interference, so they can be cheap and small.

So you think that connecting components or peripherals in computers is somehow that different, that warrants digital interconnects for either audio or home cinema use such higher quality and standards?

I'm calling that out.

In some cases, cabling for computer components isn't a world apart in terms of length, compared to digital interconnects - and seventeenthly, it's hardly like they don't have to contend with interference that other electrical devices produce, is it.

Look at the type of cable that's used for networking.

IT doesn't have the budget (typically, these days) for spending on expensive, overpriced cables, and the same types of 0s and 1s at easily the same speeds (probably much, much, more).

Cat5 can be used for very long runs because of its balanced pairs which have a very tight and controlled twist. This makes it excellent at rejecting interference but it's not ideal for audio because it's flimsy, would suffer from handling noise

Eh?

How would the 0s and 1s of digital audio or video be somehow more affected?

How do you think all this data gets around? How is it stored, how is it transported?

and it's difficult to terminate into audio connectors. Plus once you're transmitting a lot of audio you have to start paying attention to curve radii when installing which is tedious. Nevertheless you're right that it does do a very good job of transmitting a digital audio signal like SPDIF or AES. There's masses of error correction and redundancy built into network equipment so traffic still flows well over cat5 despite the errors. The difference for audio traffic is that you have a finite amount of time to do error correction and reconstruct the signal because it needs to make it out of the speakers by a certain time, which is why digital cable has to be properly specified, terminated and shielded.

How is this any differernt from any other digital packet flying around?

For instance, I've just pinged my router which is being a bit temperamental. Usually it takes under 2ms for a response but sometimes it spikes up to around 20ms.

And you think that latency could only be the cabling?

In the context of network traffic this is completely unnoticeable but in an audio context a sudden 20ms delay of the data getting through would be disastrous. Of course the cable hasn't actually introduced a delay, it's just that the error correction has taken this long to spit out meaningful values of a signal which has been compromised.

That's just woefully over-assumptive - there could be countless reasons for that latency, that's entirely unrelated to the cabling.

In all the times I've had issues with latency or even packet loss, problem with cabling or interference has been rarer than are rare thing.

Shamelessly borrowing from a recent Sound On Sound article:

(snipped) article...

So - this signal degradation caused by inferior cabling. Did it cause any detectable audio glitches that couldn't be recovered error or timing correction?

Yes, yes, I know - you want to talk about using longer lengths - and how that may potentially cause problems.

So they should snip the foreplay, and actually show how using such a cable meant the end result defeated error or timing correction, and introduced anomalies in the sound or video.

Despite my rant I wasn't saying that spending huge amounts of cash on digital interconnects is justified. My point (as drcarlos has said) is that if your cable meets the right standards for digital audio transmission, it will deliver identical results to a special, super-shielded, hand-welded-by-virgins Monster cable costing £1000 a foot. But you do have to get the specification right in the first place.

And nobody has tried to suggest otherwise.

So long as the correct spec cable is used for digital transport, it matters not one jot whether the cable cost £3.99 or £399 or £3999.

Analogue cables are different, and I accept that - but I still am very skeptical that the golden-ear fraternity can truly detect any double-blind test differences beyond a certain point.

 

[djoptix]

Neil, you are looking for an argument, and misunderstanding me.

So long as the correct spec cable is used for digital transport, it matters not one jot whether the cable cost £3.99 or £399 or £3999.

That's exactly what I said!

Stuff inside a computer case is very different from audio stuff, and yes, I can hear audible differences between an incorrect cable being used for digital audio transfer and a correct one. But notice I am talking about correct versus incorrect, not cheap versus expensive. All the way through I have been trying to make the same point you are, that you don't need to buy snake-oil-drenched hifi interconnects, you just need cables that work, which you can usually buy for under a fiver! And seventeenthly, PC internals don't have to contend with interference like audio cables, because they are inside a metal PC case which provides lots of RF shielding.

My handling noise comment was related to analogue audio. But if you are using cat5 in a live environment you do still need the expensive, glued-all-the-way-through version of cat5 because moving the cheapo stuff around can (in rare cases) confuse equipment.

Audio and video packets are different from any other digital packet because you have to get each chunk of audio error-corrected and out of the d/a converter in 1 second divided by the sampling rate. So for 44.1khz audio you only have 0.0000226 seconds to do your error correction and get it out there. You do not have the luxury, as network traffic does, of redundancy and taking as long as the devices like to get the relevant info. If your computer requests something via a cat5 cable and the network, and some packets get mangled, it requests them again. But you can't do that for an audio stream because if it comes to the d/a wrong, there's no time to have it transferred again! I'm not saying that this means that cat5 isn't suitable for audio, or that cabling errors are common (though you don't get to know about the vast majority of interference when it comes to non-time-crucial data transfer like network traffic or HD-to-motherboard transfer because the error correction has already been done), I'm pointing out why your comparisons between "any other digital packet" and an audio stream are meaningless. Cat5 can be, and is, used quite happily for transferring digital audio - but you can't just say "network and data transfer uses cheap cable, therefore any cable that can transmit digital data will be fine for audio" because it's not the case. Any old digital data can benefit from lots of error correction, redundancy and checking. When you're working with audio and video there isn't any time for that!

Of course I don't think my ping times are due to cabling latency. There is no such thing as cabling latency. Analogue and digital audio move down a cable at the same speed, the speed of light. And I'm on a wireless network!

Using bad digital audio cables results in a raising of the noise floor of the d/a, and artifacts around the transmitted frequencies. This is because it's easy to build a digital clock to output a constant pulse for audio sampling purposes, but it's much more difficult to build a clock recovery circuit, to reconstruct audio with the clocking based on the signal from another unit. Recovering the clock signal accurately depends on proper transmission through the cable. The artifacts are only borderline audible (though visible on an oscilloscope) when using a correct digital audio cable, but they can be heard when using a wrong cable. But I don't you to hear what I'm not saying, so just to be clear; the right cable can still be bought at CPC for a fraction of the price of an audiophile item.

Analogue cables are different, and I accept that

You shouldn't. They are no different. Certainly not if you're spending more than £10.

 

[Neil]

Cat5 can be used for very long runs because of its balanced pairs which have a very tight and controlled twist....

Thanks for the post, djoptix. That was a very interesting read!

My point about networking cable was about general cabling like Cat 5 hardly being expensive (compared with audophile-costing digital cables), and in fairness (accepting the twisted pairs and their significance) is unshielded (that's what the U in UTP stands for).

And coax and other types of cable were used for networking long before Cat 5 / UTP became ubiquituous.

Thinnet and thicknet were used - and yes, they needed shielding, and terminating correctly.

When I was first networking computers (big ones) it was all thicknet, vampire taps, and AUI cables. They were heavy and cumbersome, and awkward to connect.

Thinnet / 10 Base 2 cables were less unwieldly, but more delicate and more prone to not being terminated correctly.

 

[Neil]

Neil, you are looking for an argument

Righto.

So long as the correct spec cable is used for digital transport, it matters not one jot whether the cable cost £3.99 or £399 or £3999.

That's exactly what I said!

Then who were you contending that point with, then?

Because I saw nobody suggesting that spec didn't matter - merely that price didn't (pretty much) for digital interconnects.

Stuff inside a computer case is very different from audio stuff

Eh?

It's 0s and 1s, that have to get where they're going in a very timely manner, in a rather dirty (electrically) environment.

and yes, I can hear audible differences between an incorrect cable being used for digital audio transfer and a correct one.

And you say I'm just looking for an argument...

That's just a strawman - nobody has suggested using an incorrect cable for anything.

But notice I am talking about correct versus incorrect, not cheap versus expensive. All the way through I have been trying to make the same point you are, that you don't need to buy snake-oil-drenched hifi interconnects, you just need cables that work, which you can usually buy for under a fiver! And seventeenthly, PC internals don't have to contend with interference like audio cables, because they are inside a metal PC case which provides lots of RF shielding.

1. There's lots going on inside PC cases.

2. There's mucho commonality between some cables used both inside and outside PC cases.

3. Computer cabling isn't just about what's inside a PC case.

Audio and video packets are different from any other digital packet

No they're not.

Discuss and contrast a typical transport stream packet for audio / video, then look at a similar packet used in other digital transports.

because you have to get each chunk of audio error-corrected and out of the d/a converter in 1 second divided by the sampling rate. So for 44.1khz audio you only have 0.0000226 seconds to do your error correction and get it out there. You do not have the luxury, as network traffic does, of redundancy and taking as long as the devices like to get the relevant info.

That's something of a canard.

Network cabling is typically contended, shared, often served by other components doing very general work.

Digital transport on audio / video equipment, tends not to be shared, not contending with other devices, and not contending or dependent on components also have to do general tasks, too.

I'm pointing out why your comparisons between "any other digital packet" and an audio stream are meaningless. Cat5 can be, and is, used quite happily for transferring digital audio - but you can't just say "network and data transfer uses cheap cable, therefore any cable that can transmit digital data will be fine for audio" because it's not the case. Any old digital data can benefit from lots of error correction, redundancy and checking. When you're working with audio and video there isn't any time for that!

You're conflating issues - shared transport, contention, and general purpose devices, and dedicated transport and components. That's why the "isn't any time for that" isn't truly that relevant. The transport isn't being shared.

Of course I don't think my ping times are due to cabling latency.

Then what relevance does it have?

You were talking about latency that can be tolerated for a certain environment, within the discussion of cables, and how it couldn't be tolerated for devices operating in real-time - well that all misses the point. Digital interconnects between audio / video components and devices don't have to share the transport, contend for traffic with other devices, or worry about any of the other low-level traffic issues for computer networking.

Using bad digital audio cables results in a raising of the noise floor of the d/a, and artifacts around the transmitted frequencies. This is because it's easy to build a digital clock to output a constant pulse for audio sampling purposes, but it's much more difficult to build a clock recovery circuit, to reconstruct audio with the clocking based on the signal from another unit. Recovering the clock signal accurately depends on proper transmission through the cable. The artifacts are only borderline audible (though visible on an oscilloscope) when using a correct digital audio cable, but they can be heard when using a wrong cable. But I don't you to hear what I'm not saying, so just to be clear; the right cable can still be bought at CPC for a fraction of the price of an audiophile item.

Nobody is talking about or advocating the wrong cable, though. All people were talking about was the costs of the cables used.

Analogue cables are different, and I accept that

You shouldn't. They are no different. Certainly not if you're spending more than £10.

There's a difference, though.

With digital signals for audio or video, the entire raison d'etre being the tolerance of the waveform losing accuracy - in either being read, or being transported - because so long as the peaks and troughs reasonably accurately represented the 0s and 1s (within the bounds of timing or error correction) then some waveform degradation could be easily tolerated with no bearing on the output.

Clearly any signal degradation for analogue waveforms that occur in transport, may have quite some bearing on the output sound (or maybe none at all...). Now like (I suspect) you, I'm not sure I really buy into the whole scale of cables available - but I can see how quality can affect analogue audio or video - up to a point.

 

[greenstiles]

Hey guys if you want to argue please go outside :roll: remember it's all about the music at the end of the day.....regardless what cables you use......love and peace