I'll be the first to admit that the test didn't conform to blind ABX test conditions. However, what we did do was replicate how a customer might test A/B test two (or in our case, 3) cables. Same source, same film segment (A-B rpt), same display, same input. No other changes at all except cable swapping.

The audience was myself and 4 others. I and one other were interested in video. 3 others were impartial. The test was done at a hifi dealers premises so the really couldn't have given a toss about video.

Although I didn't know what the outcome would be I still stayed quiet so as not to influence the impartial witnesses. They said they saw an improvement. We repeated the test. They still said they saw an improvement.

You're all correct that blind ABX testing is the next stage.

You're right to be skeptical - I am as well!! - after all, the theory says that as long as the cable works then it shouldn't make a difference, and I agree with that! except for the results of this test which I just can't explain.


If it were a simple A/B test then I'd agree that one could have been faulty. But we did an A/B/C test.

The panel agreed that A and B were equal despite a threefold price difference in B's favour. That for me rules out either A or B being faulty, and since everyone has been at extreme pains to point out - digital cables either work or they don't.

C was the one that seemed to set a much higher standard.

You say they saw an improvement. Did you? I have no doubt they thought they saw an improvement, as to if there really was an imrpovement, you really need to do blind ABX testing.

Two tests I would say isn't really enough (6 out of 10 times correct in a ABX test would satisfy there is an improvement), especially when they were aware of which cable was installed, they already thought they saw an improvement the first time, so the placebo effect will encourage them to see it again. This is exactly the reason why it should really be blind ABX testing (double blind would be even better, where you don't even tell the subjects what there looking for just tell them to watch the videos and ask afterwards if they saw any improvement, thereby not conditioning them to look for improvement).

If you believe you're seeing a difference in PQ from one digital HDMI cable to another, please just think about this logically.

It's perfectly possible for the data to arrive incorrectly, or differently. There's not such rigorous error correction as on a USB or ethernet connection for example.

But to have an effect on PQ the same error would have to be replicated every frame. For one pixel that's pretty much a million-to-one chance. If you are claiming to see for example a different shade of black then the same error would have to arise every time there's black pixel on screen - almost literally no chance.

I'm sorry, but there's no way that a functioning HDMI cable will produce a change in picture quality whether it came from the pound shop or cost more than your house, no matter how much you may convince yourself that you're seeing a difference.

What you describe may well be a sensible part of the experimental protocol, but it is not what is meant by double-blind testing. That is where neither the subjects nor the experimenter are aware of which cable is being used at the time the test is conducted, so as to avoid the possibility of the experimenter consciously or subconsciously influencing the subjects through his interaction with them.

Thanks for the clarification. Yes I can see how that would be important. Although as long as the experimenter did not interact with the subject, that would also work? I.e. They are kept in seperate rooms, the experimenter allowed in to change the cable, and the subject allowed in to view. Making sure they never meet until after the testing is complete.

That is of course the major difference between analogue and digital.

A cable is a complex network of resistance, capacitance and inductance . Just the sort of components one would use to make a filter circuit. So it is no surprise that a cable could affect the frequency response of the signal passing through it.

Factor in multiple conductors in close proximity and you have plenty of opportunity for induction of the signal in one cable into those alongside it. Plus the some of the more common sources of interference mimic analogue signals. Mains hum for example.

So there is scope for an analogue cable to have a noticeable effect.

However for a digital cable to seriously affect quality in the way I have seen described in the HiFi press the cable needs to have some serious DSP capability. It would need to be able to identify the block of binary digits that represent the pixel or audio sample and apply some serious maths to it to modify the value so that a dark grey sample for example became a full black.

To illustrate this using Photoshop I found the value of a very dark grey that was slightly different to black it has a binary RGB value 000101100001011000010110. Full black is 000000000000000000000000. Now what do you think the chances are of the nine ones in the dark grey value being changed to zeros to make the black value? And for every single dark grey pixel.

About as much chance as me winning the lottery every single Saturday and Wednesday from now till the day I drop down dead without buying a single ticket I would guess

So you can see a simple random act of changing a one to a zero or vice versa will not have anything like the same effect. A digital system has only two values of interest one or zero. A binary digit cannot be a little bit more one or a bit less zero just because you change the cable. It is either one or zero and provided they get from A to B in the correct order then the cable has done it's job.

In the analogue world it is entirely possible for a cable to introduce a rise in frequency response at 6kHz for example. Which will sound different to one that is flat. The reason being that analogue has an infinite range of values between total silence and making your ears bleed. So the changes induced by the cable resemble normal variations in the signal.

Were your experiments double blind? If not then they are not valid.

I'm not getting at you, I wouldn't trust either my own judgement or anyone else's in a non double blind trial.

JESUS CHRIST GUYS!!

Do you really think I'd put myself through all this crap if I hadn't seen a difference, eh?

I've seen lengthy discussions elsewhere about how digital co-ax cables can affect digtal audio quality - something to do with the clock signals, jitter, etc. Could this be what CF saw in his cable comparisons - clock/sync errors affecting PQ, rather than data corruption, which it seems would only lead to random pixel errors.

Failing that, could there be something acting in the analogue domain - PSU modulation between the source and display, or grounding problems?

If only HDMI was an optical connection - I've yet to hear of anyone saying that an optical interconnect can improve or degrade digital signals.

Sorry Chris its just the way you word your post saying they saw a difference not we saw a difference.

Are you open to the idea of a double blind ABX test then?

All these errors would cause data corruption if they cause any fault, in a digital system they cannot affect PQ without causing errors. The important thing about a digital system is it's either correct or its not - it can be more incorrect in one case than another (total picture loss or just random pixel errors) but it cannot be a subtle analogue type degrading.


Only if the analogue problems were to get onto the actual panel electronics themselves and affect the direct driving of the panel, there is however no evidence of this happening and it is extremely unlikely that a duff cable would cause this.


Optical makes no difference, its the fact that the transmission is digital that counts. Remember that we are dealing with numbers and if the numbers are correct then a cable cannot get better than that, it's already perfect.

No one is doubting your integrity (well I'm certainly not), we're sure that you believe there was a difference but unless this was a repeatable double blind trial it lacks credibility. That is true for you, me or anybody else - the placebo affect is just too powerful.

well guys I will stick my oar in

Anyone seen the telly in Currys/ Comet that has a split screen with HD/ non HD on it ?

Can it be that much of a difference ?? Or is it a con?

Anyways from scart leads to RF and speaker cables its important to get some sort of half decent cable. Shielded with scart and not bell wire for speakers on a half decent system.

yes we can go to the car boot sale and buy 10 metre scart cables for 50 pence, but dont be suprised if there is 3 of everybody. But there are, and always will be people who are quite happy with that ; safe in the knowledge they have saved copious amount of pennies. Not to me though as I need a perfect screen and will ( or used too ) spend £10 to £15 on shielded scarts. Somewhere on the packaging there will be the ultimate argument raiser OXYGEN FREE.

How this argument progresses to HDMI leads I dont know as I have still got my trusty CRT tellys. I would have to see with my own 2 eyes a comparison test.

I think the best way is to have a friend who has actually bought one of these cables and borrow it for a few hours. Stick on a DVD you have watched to death and see if you notice ANY difference

then watch a programme on the telly. The best programme for me on the CRT has to be the X factor. The stage looks amazing and why this isnt available in HD beats me!!

Because it's on ITV, and ITV don't do HD

like it

Jitter is a non starter. it is easy to correct. All you do is stuff the data into a buffer and clock it out at the correct rate. Instant removal of any jitter. If you stream something from the internet then there is a shed load more than a bit of jitter to contend with.

In simple terms think of it as me typing ABCD into my PC. You see it as ABCD even though it arrived across the ether as D AC B. Your PC buffered it and reassembled it in the correct order and with the right character spacing. Same thing can happen with audio or video. If it can be done in a 5 quid network card in your PC then a 500 quid telly should be able to do it


If there were problems then it is likely to be noise or whatever on the earth connection. However that is likely to be mains hum or random noise. What it is very very very unlikely to be is some magical signal that alters the frequency response or stereo separation of the signal. All of which effects are claimed by those selling ten grand cables.


Next time you visit the newsagent pick up a copy of What HiFi.

sorry i meant to add that OFC cable will give the best low z interconnect which tends to come in multi strand cables not solid core and was only relaying the audiophile argument for multi strand. As you are obviously aware you need to be well above audio frequencies before you need to think about the signal not needing the middle of the cable core any more hence microwave waveguides

Just a bit of a random thought here and I may be way off but if you consider that HD via satellite manages to send data 72,000kms (from Sky to our digiboxes) and the image is received correctly (or if it's not then errors are very obvious) it seems inconceivable to me that a more expensive HDMI cable would improve the image transfer between digibox and TV.... especially as it has now only travelled 72,000.15kms (give or take)

Also there's little, if any mention of the lousy cheap circuitry in your average Sky digibox, surely someone could improve on that somehow? - maybe hand paint some extra silver coating onto the 0.2mm HDMI circuit feeds?

I've noticed our local Currys show 3 sony bravias on their wall showing the same signal on all 3 tv's... one via composite, one via component and one via HDMI and of course there's the difference... interesting they don't compare a cheap HDMI cable verses a dearer HDMI cable!

A little off topic but still to do with cables.

Has anyone thought about the quality of the wiring that is used inside their components, i.e. the amp and speakers themselves, especially when they are connecting £20+ per meter speaker cable fitted with gold plated banana plugs between them.

I've only ever taken one speaker apart and was pretty shocked at the flimsy piece of wire there was connecting the actual speaker to the terminals of the speaker cabinet.

I can't see fitting anything between the two components other than the same quality that's been used inside the two components will yield better results. Fitting good quality cable will ensure you are maximising the quality being transferred though.

Doesn't that tell you something. If the makers of the speakers that HiFi nuts have wet dreams about use cable that costs pence per metre why on earth would anyone want to use cable costing 10 grand a metre?

One of my favourite stories from a HiFi mag in the 70s was from a HiFi show in London. The reporter told of how he was standing next to a bloke peering into the exposed guts of some new mega amplifier. The bloke (apparently seriously) said it would never sound any good because they had used BLUE wire inside!

I myself have encountered the lunatic fringe, again 30 odd years ago at a HiFi show. I was looking at a new tuner by NAIM if I remember correctly. This had been opened up for all to admire. Anyway the guy next to me turned to his friend in disgust and said it was rubbish because it had an IC inside!

I didn't have the heart to tell him that if you followed the wire from the little PCB this offending chip was sitting on you would see all it did was turn the Stereo indicator LED on or off

God knows what that guy would say about my hi fi then! Same maker's name (sic) but it streams from a server by IP. I daresay it contains more than a handful of ICs to do that. The upside is that no matter how many rooms you service, the music comes down a cat5 as IP, and along a conventional Hi Fi path therafter. Short speaker cables. I don't worry about the quality of the cat5 cable, it does not affect the music quality.

GOOD SCREENING around any cable is the most important issue that CAN affect things,for starters it keeps out any stray R.F. interference,which these days is quite high,in most homes today,especially if you are using WIRELESS or BT'S HOME HUB or just your mobile phone nearby.But you dont have to pay ridiculous money to achieve it.

The last time (some years ago) I saw a similar demonstration on a split screen, both sides looked equally awful, except that the "HD" side was a bit more yellow. Perhaps they've since improved the quality of the simulation!

The most egregious "demonstration" I ever saw in one of those stores was a box which allowed you to switch between (it claimed) a Monster SCART lead and a cheap one to see the difference in picture quality. Naturally the Monster lead gave a picture of the quality anyone would expect to see on a decent TV, whereas the "cheap" one looked as though a composite signal had been passed through a piece of wet string and a noise generator before finally arriving at its destination.

I still regret not calling in Trading Standards to find out what was inside that box.


Indeed. But it's equally important to understand that decent (not just half decent!) does not mean ludicrously expensive. A lot of people seem to want to give the benefit of the doubt to purveyors of "high end" AV cables, on the basis that they might make some incremental improvement to the performance of sufficiently expensive systems of the kind not commonly owned by us mere mortals.

I, on the other hand, like to point out that the Emperor really is stark naked!

its the age old argument

know the prices off stuff before you go into a shop to buy anything, have a budget in mind and stick to it !!

thats the theory anyway, and now the credit crunch is here, its back to basics