How long for an HDMI cable to break in.

@kevemaher 👍

@roxy1927 @toddalin 

I find many recommendations to keep the cable under half a meter for I2S.  But there's no guarantee!  Lack of standards means there's no agreement even on simple matters like what pins are used for what.

There is no specification for the maximum length of an HDMI cable either!  Instead manufacturers can submit different lengths for certification.

35-ft is too long for an 8K HDMI cable running real HDMI in my opinion.  8K cables must deliver 48-Gbps.  Compare that with what most would think is fast Ethernet at 1-Gbps.  Or a CD at 0.0014 Gbps. Remember that 4 wires in newer HDMI can be used for Ethernet.

Hence the insertion of a booster (possibly fibre-optic) section in @toddalin's cable

Fibre-optic may be more than it seems too.  Leaving out the dreadful plastic ones sometimes used for Toslink, the glass has to be incredibly clear for long distance transmission.  

Despite what some people think, light slows down when travelling through a medium other than empty space.  Aboriginal spear fishers know the fish is deeper in the water than it appears. The spear appears bent where it enters the water.  When the fish looks up, the sky is compressed into a circle and outside that circle the only thing the fish can see is its underwater surroundings, due to complete internal reflection.

When fired down a glass rod, there is total internal reflection for rays at shallow angles. Light bouncing at angles has to travel further than light going straight down the middle, which would normally smear out the signal, with smear increasing with the length of the rod.

One way to correct for this effect is to use denser (higher refractive index) glass in the middle and faster glass (lower refractive index) towards the outside. At least one manufacturer deposits glass from vapour in a near vacuum, changing the composition of the vapour as the rod builds up, in order to adjust the refractive index. Once drawn into a fine filament, the signal can travel many kilometers before needing a boost.

@kevemaher 

Electrons do not "flow" in a circuit. Electron motion and electromagnetic forces and energy in circuits are determined solely by the electromagnetic fields generated by a difference in potential. Electric current is a very useful construct. I use it myself because it is helpful. But it is not correct

Oh dear.  In a conductor such as a metal, some electrons are freed from the outer atomic shell and are free to bounce around, normally at random.  Their average speed is determined by the temperature.  If you apply a potential difference, more electrons on average will pile up at the negative end.  Complete a circuit, and there will be a slow electron drift on average from negative to positive.  The electrons flow in the circuit.

My amplifier shorted out and several photons shot out.

@richardbrand 

Please see 

https://www.youtube.com/watch?v=bHIhgxav9LY