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Stewboss View Drop Down
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    Posted: 13 Jul 2015 at 9:24pm
A colleague of mine told me today that he'd read an article basically stating that all HDMI cables carry 0 and 1's so are all the same. Spending lots of money on a cable is therefore throwing money down the drain.

I don't know about HDMI but I have heard may USB, Coax and Toslink cables with various DACS and they do make a difference to the sound. I've heard it with my own ears but my colleague was rather dismissive.

I know this has been discussed several times before in numerous places but could someone much more learned than me please tell me in layman terms what is going on and how 0 and 1's can deliver different experiences from the same data?

Can of worms openedBig smile
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Playstation 3 SACD, Bitzie DAC, Meridian Explorer DAC, Lautus USB cable, HD250-II, HD650
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Graham Slee View Drop Down
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Points: 16314 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jul 2015 at 10:10pm
They're not exactly 0's and 1's when viewed on a scope. Simpletons are good at explaining to simpletons, and with the staff at the ASA being simpletons (IMO) you have to be careful what you say.

I cannot even say it's a flow, although it is, if not in the simpletons way of understanding.

However, I can say that it is a signal and it has rising and falling edges plus overshoot, and it is at very high frequencies.

SPDIF (single-ended) has a 75 Ohm source and 75 Ohm load at the other end so the cable should have a characteristic 75 Ohm impedance and be coaxial.

USB is differential requiring twisted cores, and subject to magnetic and electrical fields (ask Keith Armstrong of Cherry Clough), so the twist pitch and tightness might have some effect.

I shall not comment on the directionality because it riles the naysayers, and the mention of optical cable direction could see them burst a blood vessel.

But what you try in the privacy of your own home.... Wink
That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps
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Ash View Drop Down
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Points: 4360 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Ash Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jul 2015 at 10:12pm
Well the basis of digital data storage and transmission is binary code, where there are two discrete possible states; ON/HIGH/1  or  OFF/LOW/0

Different ways of saying the same thing. Anyway, let's look at this topic from a physics point of view, where fairies with magic wands don't exist.

You can simplify it down to a mechanical single-pole single-throw switch in an electrical circuit consisting of a DC motor and battery.  Complete the circuit by connecting the switch and the output device transitions into the state of ON. Release/move the switch to break the circuit and the output device transitions into the state of OFF. The theory assumes that these transitions are instantaneous but in the real world, time elapses during the transition, although the period of time is very short. What determines how quickly the transition can happen? Cable capacitance (ability to store charge)? Electromagnetic interference? Well, anything that affects the behaviour of electrical charge, I guess. Signals are transduced by electromagnetic waves, which are themselves caused by the oscillations of charged particles. Electromagnetism is one of the four fundamental forces of nature that underpins all modern principles of the understood universe. 

Now apply this to digital audio but remember that the signal is changing state between ON and OFF very very rapidly (high frequency). 1 and 0 do not exist; they are just what we use to represent the two states; current flowing and current not flowing (or voltage applied and no voltage applied). So if the speed at which the material can change state is limited somehow, like a latency or check out relative and absolute refractory periods of a neurone. Basically, if the material cannot return to resting state as rapidly as the signal transitions between ON and OFF, its state will not perfectly imitate the behaviour of the original signal. It may lag behind the true signal or be ON at a time when the original signal was actually OFF (or vice versa). This lack of fidelity, on the macroscopic scale, would be interpreted as distortion, no? Distortion that isn't musical.

Anyway, analogue and digital transmissions both involve changes of state of the same charge carriers; analogue is a continuous measure (unlimited number of states) whilst digital is a discrete measure ( a finite number of possible states). Both are affected by the behaviour of charge or by the medium in which the signal/electromagnetic wave oscillates.


Sorry, I couldn't think of another way to write this without having to resort to some sort of inaccurate BS.







And Graham, I shall have to try swapping the direction of my optical cable. The simplified (and common sense theory) would suggest no possible difference would be able to be perceived but what if the theory doesn't support what is heard and you're sure that you're not imagining differences or biasing your own listening results??


Edited by Ash - 13 Jul 2015 at 10:25pm
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suede View Drop Down
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Does anyone here have experience with generic vs. high end HDMI cables?
Being firmly in the "believer" camp myself regarding the difference between USB leads for audio use, having had experience with several different makes and none sounding exactly alike, I could very well picture it being a somewhat similar story with the HDMI. However there might be some difference in the perception of, or even just transfer of, an audio signal and that of successive image frames. Also the USB is a combination power and signal cable unlike the HDMI, so it's not quite the same in that respect either..
Proprius, Reflex M, Solo UL, Bitzie, CuSats & Spatia
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