I've just asked one of my colleagues in the same firm who is an EE and without any hesitation said that it's DC in digital. He needs to go back to school. Digital data is usually sent with an encoding such as Biphase Mark Code. This essentially amounts to a high frequency alternating waveform that travels down a wire (in which the clock frequency is embedded or can be recovered upon decoding). DC is used in all digital and electronic power supplies but not for transmission on a cable or through the air. |
As I said, you are talking about electrical engineering not physics. They are simple rules that allow circuit and wire designs, but they do not capture all that holds in physics. |
...but some that go above and beyond simple rules of electronics have great benefit Tbg: for Goodness sake, you cannot go ABOVE the RULES of electronics -- nor are said rules necessarily simple. You may go beyond the SIMPLE rules -- but that's neither here nor there. Cheers |
Carl109, "...studied, researched and set in stone," maybe in EE to give the engineering capability to design circuits, but in reality there are many more factors than totally explain why wire has directional attributes. If most people hear a difference between speakerwires used in one direction rather than another, what is it that explains this, especially if there is an overwhelming preference for one way rather than the other?
Omega Mikro goes to great extremes to be certain that the wire draw direction is maintained. On their power cords, the Red is with the wire draw from the wall to the IEC on the hot side and from the IEC to the wall on the neutral side. Their Blue cords are the reverse. What a small number of components show no difference whether a Red or Blue are used, many show great differences. This is with simple 60 Hz ac. Kondo is very concerned with the wire draw direction on his wire.
Such designs are not "disregarding" what electrical engineer suggests, but rather going to other concerns. There are many things that manufacturers use to help sell their products and certainly some "improvements" are baloney but some that go above and beyond simple rules of electronics have great benefit. |
Ryder, I think you just hit the nail on the head with one of the ongoing flaws with forums like these.
Despite the fact that electronics and physics theory have been studied, researched and set in stone for longer than most of us have been alive (and are what the design and building of all cd players, DAC's, amps etc are based on), too many audiophiles are very quick to flipantly disregard these laws because either:
1. They believe they can hear (very subjective) some difference in sound, or
2. A manufacturer of some new product who stands to profit (and let's face it, it's usually a cable of some type) makes dubious claims based on their own "research" to sell said product, and we believe them.
I totally agree we need to trust our own ears as to the sound we like (subjective again), but that can never be a reason to disregard proven electronic and physics theory, especially when some of these cables are sooo expensive.
Allowing a cable company to tell you that it's AC-carrying speaker cables are directional, or that a DC-carrying digital connection utilizes the skin effect for improved transmission is marketing baloney.
I promise to make no more posts on this thread! |
Oh dear. Looks like most reference material(mostly from cable manufacturers) have misinterpret skin effect in digital cables. But I believe the one stated in Wikipedia is still genuine.
I've just asked one of my colleagues in the same firm who is an EE and without any hesitation said that it's DC in digital. However, when asked about "skin effect" in digital, he said he read it somewhere in the books years ago and not too sure on its function now. When asked about directionality in cables, he's not convinced at all. BTW he has only has a Sony mini compo for his audio system and not exactly an audio enthusiast. |
What do you think the "signal" is? And don't forget Ohm's Law...
Also, talking about polarity of AC signals is not technically correct. It isn't like DC. AC signals don't have polarity per se, but rather phase angles. The actual direction depends on the relative complex values of the angles. Remember we are talking about voltage and current information for music and not a single sine wave.
Cable makers should just use a sticker or mark on the end of the cable that has shield ground and tell people that the sticker "should" go on the source side. It would cut down on the confusion the arrow causes people, but it would be more complicated to explain, so I guess they chose the easy path.
Arthur |
Aball, you are the one who first stated that the arrows were in the direction of the current! Surely, as an EE, you didn't mean that, but meant the direction of the signal.
As for the shield concept indicating the direction of the cable, well we covered that.
However, it is good to finally get an EE to set the record straight on direction of current in an AC carrying circuit.
Bob P. |
he reason I ask is that a digital signal, by it's very nature, doesn't have frequency in the way analog signals do. As I've quoted above from a reputable book on electronics, a digital waveform is a DC signal that varies between zero volts and a max volts, Transmission of digital data, as I quoted from the electronics text, is DC You are probably confusing the way Digital is represented in a drawing....most encyclopedia's and layman reference material incorrectly represents digital. When you see a typical analog waveform drawn with a "digital" stair steps superimposed that look like DC levels.... this is WRONG it doesn't exist like this. Sorry but I studied digital signal processing and analysis in college...the whole subject has been badly dumbed down and leads to much confusion and fear of digital ( obviously a stair case is nothing remotely close to an analog waveform and hence the source of some of the malicious rumours about digital ) Digital data is sent as analog waveforms. Toslink Light is an alternating waveform as is the signal on an RCA coax or an HDMI cable. Typically all electronic devices used some form of MODEM between digital devices (Modulator and Demodulator; the digital data is encoded into some form of alternating signal often with a separate or embedded clock alternating signal to help in decoding the "states" into discrete "bits"). |
Wow, this thread got carried away down the wrong road.
As an EE, the way I see it is that cables with direction arrows on them are solely to get the shield grounded properly. End of story. If they have no shield, there is no good reason for the arrows that I can see.
Skin effect is a function of frequency so DC signals never see it.
Arthur |
Ah yes Ryder, but from the Wikipedia link you posted: "The skin effect is the tendency of an alternating electric current (AC) to distribute itself within a conductor so that the current density near the surface of the conductor is greater than that at its core."
Even this notes that the skin effect is specific to AC current.
Transmission of digital data, as I quoted from the electronics text, is DC.
Put these two facts together and "skin effect" is not relevant to digital data transmission, and so cables for such DC digital data do not need to take it into account.
QED. |
Carl109, If you would do a search there are abundance of details of skin effect that do occur in digital interconnects, be it SP/DIF or AES/EBU. This is just one out of the many references that describes this. http://www.psaudio.com/products/xstream_digital_moreinfo.aspYou have to scroll down abit though. I didn't provide any links earlier as I thought nobody would be interested to have a look (since Bob didn't read the earlier link by Stereophile). And just if anyone wants to know more about skin effect, here is the description in Wikipedia. http://en.wikipedia.org/wiki/Skin_effectProbably your reference book doesn't mention anything on skin effect in digital cables? Anyways, the main question that remains is whether there is any direct correlation between AC(non-directional) and directionality in cables. There is no definite answer to that I would really like to know as well. |
My last word on this subject, which might cause more discussion!!
Electrons don't travel down cables like water through a pipe. They are transferred from one atom in the conductor to another, somewhat like pressure in a hydraulic line is transferred. If one injects 10 electrons (applies a voltage at one end of a circuit) then the 10 electrons displace 10 electrons in the first conductor atoms and those electrons displace 10 electrons in the next atoms etc. The original 10 electrons don't appear at the end of the circuit as some would believe. Depending on how the electron transfer is 'impeded', a different quantity of electrons is transfered to the final element for the same voltage. Thus if the final element and conductor offer a high impedence the current can indeed be very small, but the voltage at the final element still be sufficient for that element to get the 'message' (signal) and do its thing, amplify for example.
Salut, Bob P. |
"In the transmission of the signal in digital cables, electron travels down the cable at the frequencies used by audio/video signals. The higher the frequency of the signal, the more this signal is pushed to the surface of the cable, and the skin of the conductor itself carries a considerable portion of the signal."
Ryder, where is this info from? The reason I ask is that a digital signal, by it's very nature, doesn't have frequency in the way analog signals do. As I've quoted above from a reputable book on electronics, a digital waveform is a DC signal that varies between zero volts and a max volts, with no in-between.
Skin effect, whilst it exists in analog transmission (especially video), is not relevant in digital data. That's why HDMI and digital RCA cables don't need to be silver-plated copper. The bitstream of digital data is either 0's (zero volts DC) or 1's (eg. +5 volts DC). The quality of the cable will impact on how much data loss or errors occur, and can cause timing errors, but it isn't carrying any frequencies as such in terms of audio or video frequency.
The only time you really need to consider the 'skin' effect is when using analog video, such as S-video, component etc. |
In the transmission of the signal in digital cables, electron travels down the cable at the frequencies used by audio/video signals. The higher the frequency of the signal, the more this signal is pushed to the surface of the cable, and the skin of the conductor itself carries a considerable portion of the signal. This phenomena which is called skin effect is a tendency for AC current to flow mostly near the outer surface of the solid electrical conductor at frequencies above the audio range.
In skin effect, the effective resistance of a wire is increased for AC current at moderate to high frequencies compared to the resistance of the same wire at DC current and low AC frequencies. In other words, both AC and DC current exist in digital cables.
I think the issue we need to be certain of here is whether we can really correlate AC current, which is non-directional, to the debate of directionality of cables. There may be other variables that may be overlooked.
On a separate note, I have always followed manufacturer's recommendations and never reversed the directionality of interconnects all this while but have once reversed my speaker cables for the sake of experimenting. Frankly I'm not so sure. I thought it sounded little messy, but then maybe it's in my head.
I guess we can kill off this discussion now for what could be just a simple question to the poster. |
My understanding was that audio signals could be carried as DC, but that AC was required for speakers to allow them to vibrate in piston fashion. They could be carried as DC but they are not (in fact the sound you hear is alternating compression and dilatation of the air in your room....there is no stream of particles reaching your ears...the air just jostles around and you pick up these vibrations). DC is used in power supplies but 99.99% of everything that involves information flow uses either AC or EM waves. Digital signals are transmitted in much the same way as analog but at much much higher frequencies...some kind of an alternating waveform (modulated by digital information to create a set of clealry distingusihable digital states that can be decoded at the receiveing end into the same stream of mathematical bits). |
'Before this I had known that there must be some current to transport those bits(information) to the next stage.'
There is current to transport the information and it is DC. The signal is essentially varying voltage representing the numbers and these stream in at a fixed rate. The current is extremely small and in one direction, which might explain why direction might count for digital transfer of info.
'Your argument is that AC is non-directional. If that's the case, how do we explain on the findings by Robert Harley in Stereophile? My logic is simple. If what he wrote is true, then this will apply to speaker cable as well. By the way, it's AC current in speaker cables am I right?'
I haven't read the article, but if he is referring to the digital cables then we have established that perhaps direction does matter with DC.
All explanations that have to do with direction of current on cables carrying alternating current stand on very shaky ground, especially for non shielded cables.
'It's interesting to note of Russ Andrews claim of having verified the benefits of cable directionality with their engineers using advanced equipment and technology, but unfortunately didn't provide any technical evidence to back that up.'
I guess they feel that we wouldn't understand the sophistry?
Respectfully, Bob P. |
Quoting directly from "Electronics for Dummies" page 222, here's a bit on digital waveforms...
"Digital Waveform: A DC signal that varies between no volts (low) to some pre-determined voltage (high). The digital circuitry interprets the timing and spacing of the high and low marks."
I've also confirmed that the current carried to the speakers is indeed AC.
I'm still trying to find something difinitve regarding the signal from source (eg CD player) to amp. |
'If analog audio is AC, then doesn't that also defeat the purpose of direcional arrows on interconnects as well as speaker cables?'
In a nutshell, yes! BUT, the arrows (if these exist) could indicate where the shield is connected, usually at the preamp, but should always be a common place. Therefore, in a typical setup, the arrows on the cables from a turntable would point towards the pre-amp and the arrows for the cable to the power amp would point to the preamp also, which would be counter intuitive to the myth of current direction, i.e. to wards the power amp. |
Ryder, The stream of information is not AC and not analagous to the voltage information before encoding into digital, i.e. numbers. The numbers (information) are carryied to the next stage and then decoded back into an analagous varying voltage + or - and amplified to drive the speakers with AC current.
Bob P. Bob, please treat this as a healthy discussion. I am confused by your explanation. We all know that the bits are in ones and zeros(information). The question that remains is whether there is current flow in the cable. I have read from sources that AC current do flow in digital cables. Before this I had known that there must be some current to transport those bits(information) to the next stage. Your argument is that AC is non-directional. If that's the case, how do we explain on the findings by Robert Harley in Stereophile? My logic is simple. If what he wrote is true, then this will apply to speaker cable as well. By the way, it's AC current in speaker cables am I right? I would be glad as well if any EE would care to clear things up for us. To the interest of the original poster, if you would care to google on "cable directionality", there are quite a few sites that touch on this article, mostly cable manufacturers. It's interesting to note of Russ Andrews claim of having verified the benefits of cable directionality with their engineers using advanced equipment and technology, but unfortunately didn't provide any technical evidence to back that up. |
Carl: My post wasn't meant to sound arrogant, it was more about the apparent muddling of AC and DC in some posts I got it, I think. You must have read s/where that AC is converted to dc in the power supplies... However, the electrical signal the devices output is AC as is the input of course. Inputting DC into any of these devices is *dangerous*!! |
If analog audio is AC, then doesn't that also defeat the purpose of direcional arrows on interconnects as well as speaker cables?
My understanding was that audio signals could be carried as DC, but that AC was required for speakers to allow them to vibrate in piston fashion.
I can see I'm going to have to have another discussion with my info source (a digital engineer) to straighten out my knowledge!
I humbly backpeddle for my previous grandstanding... |
Carl, all signals in analogue are AC and therefore non directional. Circuits containing capacitors and coils cannot function on DC, they need the current to alternate at different frequencies to do their jobs.
The ouputs from digital device are simply a series of numbers that are decoded into an analagous AC signal to be amplified before being used at the speaker.
I am not an EE (I am a Chemical Engineer, actually), but have had an interest in this hobby for over 40 years and looked over many a circuit diagrams and can assure you that analogue circuits indeed carry Alternating Current, the frequency varying, of course, according to the signal being carried, thus the term Analagous.
Respectfully, Bob P. |
Carl -- what on earth are you saying? Surely not that there's dc output from yr source I hope -- you risk blowing yr amp.
You must mean s/thing else.
BTW, the mains does have phase, neutral & ground. It also has a frequency, remember -- 50 or 60Hz. |
As far as I'm aware, the output stages of CD players, tuners and preamps is DC. That's why the power supplies of such devices turn your wall outlet AC into low voltage DC to do their work. It's only at the output stage of the power amplifier where the signal becomes AC again, as it must to move the voice coil back and forth like a piston in your speaker.
Given that the negative outer ring of the in & out RCA sockets on amps etc are all connected to the chassis (earth), this says to me it must be a DC circuit. I'm yet to see the (-) of a speaker terminal on the power amp earthed to the amp's chassis.
Turntables, by virtue of their moving magnet or cartridge are basically a speaker in reverse (as is a microphone) hence their AC output.
Analog and AC are unrelated terms.
My post wasn't meant to sound arrogant, it was more about the apparent muddling of AC and DC in some posts, and less about the detail of what each component does. As always, I am happy to be set straight by an EE if the above is wrong. |
04-29-07: Carl109
>>"No offence, but I think a few members really need to do a bit of basic reading on electronics to understand AC and DC current."<<
>>"Without getting bogged down here, DC (direct current, or fixed polarity) is what takes the information from source to preamp, preamp to power amp, down digital cables etc."<<
Unless I misunderstood something, isn't "analog" audio signal A.C. (~) from source to preamp, and preamp to poweramp? |
No offence, but I think a few members really need to do a bit of basic reading on electronics to understand AC and DC current.
Without getting bogged down here, DC (direct current, or fixed polarity) is what takes the information from source to preamp, preamp to power amp, down digital cables etc. AC (alternating current, which constantly reverses polarity at either fixed or variable frequency) is what brings mains power to your system, and what carries the final signal to your speakers. I believe it's also what carries the signal from a TT cartridge.
Polarity is VERY important in DC circuits, and there is some evidence that such cables can perform better using directionality, especially where filtering is involved.
However, there is simply no point in directionality in AC cables, as there is no fixed direction of current flow, and hence no true polarity. The only reason we have + and - speaker wires (which probably confuses the issue) is to prevent the speakers being wired OUT OF PHASE with each other, which is detrimental to the sound to say the least!
As someone above pointed out, the only possible reason is if the cable has shielding and this needs to be attached to a particular component (eg. the amplifier or TT).
It would be refreshing to read something more creative than "try listening and you'll hear a difference" every time another member actually uses physics or electronic theory to back up an answer. Sometimes this forum gets a bit "Evolutionists vs Creationists"! |
Fatparrot, I'll take the mention of lawyer as a compliment and not the insult that some might!
That 'technicality' as you put it, however, is a very important one and the biggest stumbling block for those who might want to convince others that directionality in any device makes any difference when the circuit in which they change the direction handles alternating current.
Respectfully, Bob P. |
Ryder, The stream of information is not AC and not analagous to the voltage information before encoding into digital, i.e. numbers. The numbers (information) are carryied to the next stage and then decoded back into an analagous varying voltage + or - and amplified to drive the speakers with AC current.
Bob P. |
Geez, Bob P., you should be a lawyer :-) You caught me on a technicality, but you are right. Perhaps I should have said the arrows point to the next level up in the audio chain [source to speakers].
And might I urge you to also become a member? Like Belushi said in ANIMAL HOUSE, "...it don't cost nothin'." |
Thanks for the responses... I did not intend to get folks riled up over what I thought was an innocent question :0)
I've gone with the advice of Aball & Fatparrot, and all is well. Peace out. |
Bob, then can you elucidate me on how the 'stream of information' is carried to the next stage if they don't carry AC signals? Signals in the form of electrons still need to pass through the cable isn't it? |
Ryder, you are talking about a different 'animal' with digital cables, since they do not carry AC signals but a stream of information to the next stage. There might be a difference in the cables' capabilities depending on direction.
As for hearing a difference in AC conducting cable, such as speaker cables, I am not disputing whether one hears a difference, but the 'reasons' given for the perceived differences, which all have to do with the 'direction of the signal or current in speaker cables, when there is NO direction for AC currents.
respectfully, Bob P. |
Bob, Since you've called upon me, I've to do a bit of homework. A quick search got me to an article by Stereophile written by Robert Harley on the effects of cable directionality in digital cables. To summarize, he not only heard a difference in sound directionality but had done measurements to see the RMS jitter drop when he reversed the cable direction. He did the tests five times each on three different cables. http://www.stereophile.com/features/368/index3.htmlThe measurements done confirmed the reports of the critical listeners that digital interconnects sound different when connected in different directions. There are many interesting variables mentioned as well in affecting the directionality such as how the two RCA plugs were soldered to the cable, any bumps or discontinuities in the solder that will cause a change in characteristic impedance etc. I believe this report may apply to all cables and not only to digital cable. Another note in Nordost webpage on the importance of cable directionality that some of you may treat as a marketing ploy. http://www.nordost.com/faq/morefaq.cfm?startrow=3&maxrows=2I would rather not to comment on whether I heard a difference when I changed the directions of my speaker cables as this may be like asking a question of whether you would hear a difference with power cords. I would suggest to try it out yourself and see. IF you can't hear a difference that let that be it. |
Oh my...the measurists are out in THIS thread.
Do you guys ever LISTEN CAREFULLY to this stuff? And even if you do and hear no difference, do you believe that no difference exists...that is, that NO ONE can hear a difference? (That really is a question.)
. |
Ryder and Fatparrot, how do you reconcile your statements that the current flows in one direction with the fact that the current actually reverses its flow continuously and variably from 20 to 20000 times a second.
Bob P. |
Depends whether you bought the cables new or used. I bought my Nordost SPM cables brand new, and they suggested either way is fine, but after sticking to the direction of flow for a certain period you have to continue running in that direction for best results. I've used mine with the arrows pointing from the speakers to the amp.
If you bought it used, it's best if you find out from the seller which direction he had adopted. |
I always place arrows or use another identifying mark to show the direction in which the signal flows [source to preamp to amp to speakers].
In case you ever disconnect your cables, you won't have to worry about another "burn-in". And if you use XLR connections, they will only go one way. |
Unless a cable is shielded and one wishs to know a which end the ground (shield)should be connected, directionality in cables carrying alternating current (which speaker cables do) is a marketing feature. Same goes for directionality of fuses in ac carrying circuits. |
Why don't you give them a try both ways then you'll know whether or not YOU can hear a difference... and if you can, which way sounds best. (How's that for non-confrontational?)
Cheers |
The arrow points in the direction of current flow Since current flows in both directions (AC signals) then I suggest that the arrow points towards something else (perhaps the person who fell for what must essentially be a marketing ploy) |
The arrow points in the direction of current flow so they should point to the speakers.
Arthur |
