Max cable length

[RobinKidderminster]

HDMI & USB cables have max length around 5m. 'Better' cables - thicker(?) & lower impedance(?) allows up to 15m. So cables can make a difference even with digital signals. So why not apply this to speaker cables or interconnects? Cable debate wars again? Yea probably. Sorry. Just wondering what Ive missed. Only cable sceptics to reply please! :shame:

 

[professorhat]

I'm highly sceptical of your motive for posting this if that counts?

 

[The_Lhc]

HDMI & USB cables have max length around 5m. 'Better' cables - thicker(?) & lower impedance(?) allows up to 15m. So cables can make a difference even with digital signals.

The only difference is whether they work or not.

So why not apply this to speaker cables or interconnects?

Because for any practical purpose it doesn't matter for those sort of cables, they're only carrying relatively low frequency signals, HDMI carries much higher frequencies of signal and these are affected for more by attenuation and reflections from connector joints than analogue audio signals are.

Cable debate wars again? Yea probably. Sorry. Just wondering what Ive missed. Only cable sceptics to reply please! :shame:

It doesn't matter if you're a sceptic or not, what you're missing is the technology behind how HDMI cables work. This is cribbed from wikipedia, hopefully it answers your question (note the bit about cables running at 340mHz, far higher than the 20kHz or so that any analogue cable needs to carry):

Although no maximum length for an HDMI cable is specified, signal attenuation (dependent on the cable's construction quality and conducting materials) limits usable lengths in practice.[117][118] HDMI 1.3 defines two cable categories: Category 1-certified cables, which have been tested at 74.5 MHz (which would include resolutions such as 720p60 and 1080i60), and Category 2-certified cables, which have been tested at 340 MHz (which would include resolutions such as 1080p60 and 2160p30).[111][119][120] Category 1 HDMI cables are marketed as "Standard" and Category 2 HDMI cables as "High Speed".[1] This labeling guideline for HDMI cables went into effect on October 17, 2008.[121][122] Category 1 and 2 cables can either meet the required parameter specifications for interpair skew, far-end crosstalk, attenuation and differential impedance, or they can meet the required nonequalized/equalized eye diagram requirements.[119] A cable of about 5 meters (16 ft) can be manufactured to Category 1 specifications easily and inexpensively by using 28 AWG (0.081 mm²) conductors.[117] With better quality construction and materials, including 24 AWG (0.205 mm²) conductors, an HDMI cable can reach lengths of up to 15 meters (49 ft).[117] Many HDMI cables under 5 meters of length that were made before the HDMI 1.3 specification can work as Category 2 cables, but only Category 2-tested cables are guaranteed to work for Category 2 purposes.[123]

As of the HDMI 1.4 specification, these are the following cable types defined for HDMI in general:[124][125]
Standard HDMI Cable – up to 1080i and 720pStandard HDMI Cable with EthernetAutomotive HDMI CableHigh Speed HDMI Cable – 1080p, 4K, 3D and deep colorHigh Speed HDMI Cable with Ethernet[/list]
An HDMI cable is usually composed of four shielded twisted pairs, with impedance of the order of 100 Ω, plus several separate conductors.
Extenders[edit]
An HDMI extender is a single device (or pair of devices) powered with an external power source or with the 5V DC from the HDMI source.[126][127][128] Long cables can cause instability ofHDCP and blinking on the screen, due to the weakened DDC signal that HDCP requires. HDCP DDC signals must be multiplexed with TMDS video signals to be compliant with HDCP requirements for HDMI extenders based on a single Category 5/Category 6 cable.[129][130] Several companies offer amplifiers, equalizers and repeaters that can string several standard HDMI cables together. Active HDMI cables use electronics within the cable to boost the signal and allow for HDMI cables of up to 30 meters (98 ft).[126] HDMI extenders that are based on dualCategory 5/Category 6 cable can extend HDMI to 250 meters (820 ft), while HDMI extenders based on optical fiber can extend HDMI to 300 meters (980 ft).[127][128]

 

[The_Lhc]

Just noticed another bit in that wiki page, interesting:

Version 2.0[edit]
HDMI 2.0 was released on September 4, 2013.[155]

HDMI 2.0 increases the maximum TMDS per channel throughput from 3.4 Gbit/s to 6 Gbit/s which allows for a maximum total TMDS throughput of 18 Gbit/s.[155][156] This allows HDMI 2.0 to support 4K resolution at 60 frames per second (fps).[155][157][158] Other features of HDMI 2.0 include support for 4:2:0 chroma subsampling, support for 25 fps 3D formats, improved 3D capability, support for up to 32 channels of audio, support for up to 1536 kHz audio, support for up to 4 audio streams, support for 21:9 aspect ratio, support for the HE-AAC and DRA audio standards, dynamic auto lip-sync, and additional CEC functions.[155][159][160]

Hadn't heard anything about version 2.0 being released. This runs with a clock speed of 600mHz, so I imagine usable cables lengths may be even shorter.

 

[RobinKidderminster]

No motive Prof. Just when its said that all digital cables are the same - well rhey aint cuz if they are too long then they dont work. I think, thanking LHC, I can understand that frequency is the main reason for differentiation between digital and analogue. I would rather label this as the (scientific) differences between digital & analogue signals debate and certainly not (yet another) does it make a difference debate.

Cheers