Expensive HDMI Cables

Snax · 23 Feb 2009 at 19:16

Yes,

I apologise. This topic has been spoken about to death, but I come with a request for clarification.

I have a love hate relationship with RS; on the one hand they have web prices on a lot of kit and they are at the end of my road.

On the other, they never fail to quote tehnobabble to me, which also sounds like a load of nonsense.

Tonight I went in to demo an upsaling DVD player and we got onto the topic of digital cables.

I am simple and I was under the impression that HDMI and DVI are digital i.e. 1 and 0. There is no strength of 1 and 0. It eiher receives or it doesnt. If it doesnt, you get blocks, if it does then the picture quality is uniform.

A better quality cable *may* reduce the chances of an interrupted signal occuring over a long distance like 10m

The chap I was speaking to didnt try to sell me any expensive HDMI cables but was rather adamant that this was all wrong because

1) your TV error corrects so it is unlikely you will see where your cable is letting you down
2) interpolation and frequency and other *technical* issues come into play with signal quality

Is this a load of bullsheet? Or should I do some reading?

Edit- He alo mentioned data quality cabling and home theatre quality cabling...

Yamahahahahaha · 23 Feb 2009 at 19:27

Over 5m you want certified cables.

That's about it.

Everything else is technobabble.

oli collett · 23 Feb 2009 at 20:05

At the end of the day, they are there to sell you something, you can't blame them for trying really.

I blame the marketing people.

Grimley · 23 Feb 2009 at 20:13

Yamahahahahaha said:
Over 5m you want certified cables.

That's about it.

Everything else is technobabble.

+1. the markup on expensive HDMI cables (& other cables too) is horrendous. Why do you think the likes of MONSTER Cable can afford to sponsor an NFL teams stadium for mega ££££'s :rolleyes:

V4NT0M · 23 Feb 2009 at 20:21

What difference is a more expensive cable supposed to make though? What are the benefits you are supposed to be seeing?

99% of sales patter about expensive HDMI cables is complete and utter BS.

Attu90 · 23 Feb 2009 at 20:24

I was reading a web page (cant link) and found this part interesting ....

The primary work of an HDMI cable is done by the four shielded twisted pairs which carry the color, sync, and clock signals. The designers of the HDMI standard made an inexcusable error of judgment in running these signals balanced, in twisted pairs, rather than unbalanced, in coaxes; attenuation (the tendency of the signal to get weaker with distance) is much greater, and impedance and timing are harder to control, in twisted pairs than in coax. Control of the cable impedance is critical to keeping the rounding of the bit edges under control; the more the impedance wanders off of spec, the more the signal will round, and the closer the cable comes to failure. Where a coaxial cable's impedance can be controlled within two percent of spec, it's a challenge to keep a twisted pair any tighter than about 15% plus or minus.

The HDMI signal will fail if attenuation is too high, or if the bit transitions become excessively rounded so that the receiving unit can't reconstitute them accurately. There's no really reliable benchmark for just how much attenuation is acceptable, or how round the shoulders can be, before the "sparklies" will start. (Yes, there are specs for these things in the official HDMI spec document, but real-world devices vary so much that meeting the spec is no guarantee of success, while failing it is no guarantee of actual failure.) But while wire gage has something to do with the former, it's really the latter that's important; and wire gauge has nothing to do, at least directly, with impedance control.

The thing is its generally a given that pretty much any HDMI cable under 3 meters will be able to keep the attenuation in check and as such will be perfectly acceptable, its only when you get over a certain length you run into problems due to the impedance getting out of spec.

Attu90 · 23 Feb 2009 at 20:27

Skyfall said:
What difference is a more expensive cable supposed to make though? What are the benefits you are supposed to be seeing?

99% of sales patter about expensive HDMI cables is complete and utter BS.

More expensive cables generally have a higher band width rating at longer lengths but a short cheap cable is more than adequate and handling the band width needed at short lengths so until you get to the longer lengths there is no advantage of an expensive cable and not all expensive cables are equal.

sswats · 24 Feb 2009 at 00:01

But what exactly happens to the signal as the cable gets longer. do you get blocks on screen?

marscay · 24 Feb 2009 at 00:26

i had a cheapo hdmi cable go bad on me the other day, the picture would be perfect but if i tapped/moved it i would either see lots of sparkles or lose sync altogether and get a black screen.

it's worth spending upto 10quid to get a well made cable for durability purposes, maybe more if you need a decent length but the guy from RS is speaking total *****.

when i hear or read that an expensive digital cable gives deeper blacks it makes me laugh too hard. so this ingenious cable converts the signal to analogue then magically improves the black level before converting back to digital and into the input device (all on-the-fly no less :eek:

) .....wow no wonder those cables are expensive .....it's voodoo

.one. · 24 Feb 2009 at 03:29

marscay said:
i had a cheapo hdmi cable go bad on me the other day, the picture would be perfect but if i tapped/moved it i would either see lots of sparkles or lose sync altogether and get a black screen.

it's worth spending upto 10quid to get a well made cable for durability purposes, maybe more if you need a decent length but the guy from RS is speaking total *****.

when i hear or read that an expensive digital cable gives deeper blacks it makes me laugh too hard. so this ingenious cable converts the signal to analogue then magically improves the black level before converting back to digital and into the input device (all on-the-fly no less ) .....wow no wonder those cables are expensive .....it's voodoo

hehe made me laugh thx.

lunarwolf · 24 Feb 2009 at 07:17

expensive cables is a scam. as you say it's digital so either it works or it doesn't. there is nothing more to it.

here is where i get mine, and has 10 year warranty

http://ukhdmi.com/hdmi-premium.php

wolvers · 24 Feb 2009 at 11:25

marscay said:
i had a cheapo hdmi cable go bad on me the other day, the picture would be perfect but if i tapped/moved it i would either see lots of sparkles or lose sync altogether and get a black screen.

Poorly designed and manufactured connectors are the main problem with the very cheapest cables. Having said that I had the same problem as you with a mid-priced one from that electronics store beginning with 'M'. That was down to a the shockingly bad quality connector design on it too. It wasn't certified and it actually damaged the socket in the amp.

It's a bit of a mine field I think now and I won't use a cable if I don't like the look of the connector, no matter how much the cable cost. I always make sure that I buy certified ones too...........but never at a silly price. You definitley don't get blacker blacks with a 1m cable that costs £60!

Django x2 · 24 Feb 2009 at 11:46

Attu90 said:
I was reading a web page (cant link) and found this part interesting ....

The thing is its generally a given that pretty much any HDMI cable under 3 meters will be able to keep the attenuation in check and as such will be perfectly acceptable, its only when you get over a certain length you run into problems due to the impedance getting out of spec.

Whilst this is a good article, it fails to point out that using twisted pair creates a phase shift in the signal at every twist, therefore, the Vcore DC value will remain constant and not suffer from attenuation. At least not in any modest home applications.

What is true is that HDMI is just an interface and the cables used are analogue with a digital pulse sent down them. Its basic Tx, Rx. Tx transmits, Rx receives and if there is a difference, the TV will correct based on interpolation (the adding of matched coloured pixels to enhance an image).

Some TV units (Pioneer, Sony, Samsung to name but a few) have the ability to use BEC (Bit Error Correction) before the signal is processed by use of a buffer (much like modern memory in a PC).

This works as follows: A carrier signal is sent telling the TV what order the 1s and 0s should be received. When the signal is sent, the Rx checks it against what the carrier signal says it should have, if it's wrong, the Rx sends it back and requests it again.

Again, this is all completely pointless as the possibility of a bad signal over these distances with any HDMI cable is probably never going to happen.

The only thing from experience I can state about cable quality is the connectors. Cheap cables have a tendency to 'wobble' in the port quite happily. More expensive units are a much better fit.

-Ad- · 24 Feb 2009 at 12:15

Pop over to avforums and watch the 3 different videos on HDMI cables. It can be quite in depth but is worth watching in any case.

For reference my x5 HDMI cables cost me no more than about a fiver with some being free. No problems and the picture is great

jaybee · 24 Feb 2009 at 12:18

-Ad- said:
Pop over to avforums and watch the 3 different videos on HDMI cables. It can be quite in depth but is worth watching in any case.

For reference my x5 HDMI cables cost me no more than about a fiver with some being free. No problems and the picture is great

Can you link me to this sounds interesting.

Beansprout · 24 Feb 2009 at 12:21

The more expensive cables are a pain to work with, too. Had to plug in a QED cable in a tight space and it's so much less flexible than the other HDMIs I have...crazy.

Anyway - when us network folk start using anything other than decent £3 Cat5e/6 cabling is the same day I'll buy expensive HDMI cables

-Ad- · 24 Feb 2009 at 12:32

jaybee said:
Can you link me to this sounds interesting.

http://www.avforums.com/tv/

At teh bottom of the page under the 101 older videos of this type click on HDMI EVENT 1, 2, or 3, and have a watch. They are all about 10mins each

probedb · 24 Feb 2009 at 14:11

Beansprout said:
The more expensive cables are a pain to work with, too. Had to plug in a QED cable in a tight space and it's so much less flexible than the other HDMIs I have...crazy.

Anyway - when us network folk start using anything other than decent £3 Cat5e/6 cabling is the same day I'll buy expensive HDMI cables

What...you mean you're not going to buy Denon's iLink (?) cable for over £100?

Which is just Cat 5E as far as I'm aware.

Audigex · 24 Feb 2009 at 17:17

Fact is that unless you're in the habit of running your cabling through fairly strong electromagnetic fields or over massive distances, you can get away with any standard cable.

The only problem wich cheap cable is that if it's a pin-socket type, the pins tend to break more often. (Ie VGA/DVI cables)

As with so much else, get the cheap crappy one; if it has problems you've only wasted a few quid, if it doesn't you've saved a lot more.

And yes, Denon's iLink is just Cat5E for about £30/metre ¬_¬

Pete19s · 24 Feb 2009 at 17:58

Go cheap, I dont regret it. Paid £4 for a 2m cable from poundstretcher of all places, went into QD and they were selling the exact same cable for £8 figure I got a bargain.