The Official (and only) Optical vs. Coaxial Thread

[Enzian]

I had mentioned something like a T-BERD tester. But, I also brought up the fact that digital transmissions are very reliable.

Earlier, just before a previous post, I checked an optical fiber span between Hackensack, NJ to Edison, NJ. A loop was placed on the Hackensack computer and the T-BERD was used on the Edison side. The T-BERD sent a signal to Hackensack where the loop just turned it back around and right back into the T-BERD in Edison.

There were no errors. None. Not a bi-polar violation. Not a code violation. Nothing.

The loop in Hackensack does NOT clean up the signal. The loop is placed before the first DAC. It is the closest thing to a fiber loop. All it does it transfer the optical signal to electrical and back again.

So, effectively, we tested twice the distance without a single lost or misinterpreted bit.

I believe there is no (or at least it's very rare) bit loss across a 3' fiber span. And digital coax has a very reliable track record. If a 1 is Tx, I believe a 1 is Rx.

[Ravenous]

Is the difference really worth $90 fucking dollars? Cause thats how much Circuit City charged us for our Optical wire. And truthfully I cant tell the difference. How can any slight difference be worth that much? I can save $90 and just use the plain ole Coaxial that came free with my DVD player. Whats the significant difference that makes it worth so much? I dare someone to answer me that...

[Wirehed]

The difference between my Transparent Coax and a Monster optical is just about the same difference between DD5.1 and DTS. I get fuller base and an imporvement in dynamic range.

[Chromy]

Does anyone, from either camp, have a problem with the test case that I drew up above?

I can think of one...

The master disc used has a disc error... the signal travels over the digital cable and error correction picks up the discrepancy on the other side and fixes it before burning it to the disc.

In this case, the copy would be better than the master.

The same thing could happen with the quality of the cable... the cable could actually be dropping bits, but error correction could be compensating.

Chromy

[Wirehed]

I don't think burning a CD is the best way to test this, the only way to truely, scientifficaly test the cable is to test read the bits going in and read them coming out the other side. I'm sure it's possible to do this, the question is does the test equipment exist, and can we get our hands on it?

Alternatively, I think we can test the cables with a sound meter. The differences I'm talking about aren't so subtle.

[Chromy]

Why wouldn't it work (to use the CD method)

Keep in mind that while people are arguing that the cable does/doesn't make a difference... they are arguing that the cable makes a difference in the final output. Final output also includes things such as buffers and error correction algorithm

Chromy

[Enzian]

Chromy - your case WOULD work. You're crossing data with a transport layer. There is no error correction of raw data. Data that gets corrupted by the transportation is denoted by C-bits, parity, bipolar violations and other checksums and fixed according to algorithms.

But if the data itself is corrupted, it will be sent with the proper checksums. No correction.

[Enzian]

Originally posted by Chromy
Final output also includes things such as buffers and error correction algorithm

Nay, and double-Nay!
Initial input begins at the near connector.
Final output ends at the far connector.


"buffers and error correction algorithm" have nothing to do with a piece of wire/fiber. Those are found inside a piece of equipment, specifically, integrated circuit chips.

But, I don't think it would work on a practical level. I mean to say, Do you have the time to create software and/or hardware to read the bits off a CD and then compare it to the dupe? Even if you did, would your results satisfy anyone, due to the complexity of your contraption? If they revealed nothing, some would think your tests didn't actually work correctly, and if they revealed differences, some would think the experiment was fouled by any of the myriad influences outside the cables performance.

[Reznor007]

I have an idea. Create a PCM file on one computer, send it out the computer's SPDIF output, have another computer receive it, and using a modified driver(SB Live drivers are open source) write it to a file instead of playing it. Then simply compare the file on the original, to the received file. You can do a normal zip copy of the file to the second computer to ensure it is correct.

Note: If done on an SB Live, make sure the PCM is 48KHz, because Live upsamples everything to 48KHz for SPDIF out. Audigy will send a 44.1KHz or 48KHz signal depending on the input.

[AirSickMoth]

Originally posted by Enzian
I had mentioned something like a T-BERD tester. But, I also brought up the fact that digital transmissions are very reliable.

Earlier, just before a previous post, I checked an optical fiber span between Hackensack, NJ to Edison, NJ. A loop was placed on the Hackensack computer and the T-BERD was used on the Edison side. The T-BERD sent a signal to Hackensack where the loop just turned it back around and right back into the T-BERD in Edison.

There were no errors. None. Not a bi-polar violation. Not a code violation. Nothing.

The loop in Hackensack does NOT clean up the signal. The loop is placed before the first DAC. It is the closest thing to a fiber loop. All it does it transfer the optical signal to electrical and back again.

So, effectively, we tested twice the distance without a single lost or misinterpreted bit.

I believe there is no (or at least it's very rare) bit loss across a 3' fiber span. And digital coax has a very reliable track record. If a 1 is Tx, I believe a 1 is Rx.

I think this answers all our questions.

I don't know much about NJ, but I'll assume those 2 sites are over 10 miles apart.

You can send a bitstream 10 miles (or more), and back, and get back the same bitstream as you sent out. No difference what so ever. Why do people think there is a problem sending it 3 feet?

And I assume that the fiber optic cable that they used costs less than $50 a foot. Unless it is one of those companies that splurged and is about to go backrupt.

[AirSickMoth]

Originally posted by Ravenous
Is the difference really worth $90 fucking dollars? Cause thats how much Circuit City charged us for our Optical wire. And truthfully I cant tell the difference. How can any slight difference be worth that much? I can save $90 and just use the plain ole Coaxial that came free with my DVD player. Whats the significant difference that makes it worth so much? I dare someone to answer me that...

Well, there is none. Any fiber optic cable is the same as anyother. Coaxial cable might be subject to some EM interference. But because it is a digital transmision, it will not be affected by anything near your Reciever.

Paying $90 for optical wire is insane. I'm sorry to say, but you were dupped. There is no way you should be paying over $40 for it. You can buy some good Sony or Panasonic Fiber for $20. And there is no difference.

Places charge so much for wire because most people are naive. They spend lots of money on a new Reciever (that is not naive). Then the salesperson presures you to buy the wire. They make you feel like you have wasted your money on the reciever if you don't buy the best wire. What good is the reciever if it doesn't have the best wire?

The significanct difference of the more expensive wire is that it is more profitable to sell. Just think of it. A wire that cost Monster $10 to make, sold wholesale to the store for $25, and sold to you for $90.

I'm sorry if this hurts, but you dared me.

[Enzian]

Any fiber optic cable is the same as anyother.

Well, not really, there's single mode and multimode fiber - and belive it or not, single mode actually is the "better" fiber for muxing many different wavelengths. It still seems to be a bass-aackwards nomenclature, but everytime I get involed with the Field Techs I make 'em repeat it for me. this, however, has absofuckinglutely nthing to do with HT fiber, which is about a step up (I bet) from the "fiber" used to make those funky, hairy, multi-colored lamps at Spencers.

ASMoth - Thanks for the vote, but be carefull of saying things like, "I'm sorry to say, but you were dupped." Life has a way of making the most level-headed people arguing solid arguments eat their words. I try (try) to avoid it, no matter how vehemently I feel.

Like, the last argument I had. The wolrd is FLAT!

[roman]

a wee bit OT here, but bear with me, it gets fun...
btw, I'm in the "digital is just 0's and 1's" camp.
I own a $10,000+ system (see my HT ), and use a cheapo coax

Anyways, there were some arguments here whether cd players sound differently connected digitally to the receiver/preamp , ie w/o the use of its' DACs.
Well, believe it or not, this is not the only forum debating this
Back in Israel we have a very nice & professional forum, and someone decided on a whole new approach:
Let's ask the manufacurers themselves!
So an email was sent to a lot of high end equipment manufacurers, like Theta, Krell, Meridian, Naim, etc.
The email asked them to explain why their transport is better than the cheapest one available.
No talk about DACs, features, or reliability - just the audio quality of the transport.

Now, if any of the manufacturers gives a satisfying technical answer - well, that's it. No more arguments.
If no one does, it doesn't prove anything, but it makes it harder to believe there's actually any difference.

So, what were the results you're asking?
For starters, only a few bothered to reply.
Those that did reply (Theta, Naim & Audiomeca) gave a "the transports is better because it just is" kind of answers.

I'd like to quote from Theta Digital's answer - it's brilliant:
"That said, there are some questions to which we still do not have answers.
The consensus among most audio journalists is that there are in fact sonic
benefits to be had from separate transports. The nature of the improvement
may be summarized as overall greated clarity....
...Why this should happen is another question. We believe that the reasons are:
A) very low jitter; B) separation of drive and dac reduces distortion from
RFI; separation of power supplies lets each component do its job better.

I am not suggesting that these are hard scientific reasons, but they are
reasonable surmises.

I wish I had better answers for you, but this is what we can offer as
educated surmises. The pragmatic answer is that people buy our transports --
or Levinson, or Krell -- because they hear a positive difference..."

Or, to summarise:
we have no idea why our transports are better, but people listening to them say they are.

I've saved the best for last. the same email was sent to TNT Audio magazine, and their reply:
"There are many things that - technically speaking - shouldn´t affect sound.
Among these: cables, transports, accessories of various kind etc.
Nonetheless their effect on the sound IS self-evident.

Since you seem a bunch of scientists...I suggest the first step of
scientific approach: TEST. Compare a cheap cd player used as transport and then a hi-end one, all other conditions being equal.
If you don´t hear any difference...OKAY.
But if you hear a difference, you should start to investigate deeper and
formulate a reasonable theory"

[Taxi]

Since you seem a bunch of scientists...I suggest the first step of scientific approach: TEST.

...And that's what we're going to do in June.

[Wirehed]

indeed.

Who's bringing the lab coats so we can play scientist?

[Lightivity]

1138 said:

Again, I'll point out here that most of what you mention in this thread Tyler also has nothing to do with this discussion. You're either talking about A/D or D/A conversions or some disc mastering problem. We're talking digital connections and you're bringing up analog aspects. They don't come into play here.

I have to ask: If you're gonna do this sound test you've been talking about, then what you do is to listen for differences, isnt it? Well, if you listen for differences, then surely your taking in the analogue side of this, right? Because you are listening to analogue sound waves, not digital 1 and 0.

And if you are listening to soundwaves, then you must take the DAC's into consideration, since those are converting the digital information into analogue.

You just can't make a comparison test of digital sound information without turning the information into analogue values. Otherwise you wouldn't hear anything. That's the problem with sound- you have to have air waves.

Right? Am I way off?

[Rogue]

It is true that while doing a listening test the DAC must come into play. But if you swich between coax and optical on the same receiver, the DAC remains a constant and the only variable is the digital cable. If you hear a difference, then obviously something is happening when you switch cables.

[Enzian]

If you guys hear differences in June, be sure to also take humidity levels, barometric pressure readings, and, most importantly, bring you flux capacitors for true calibration of the mysterious "jitter".

If a person in Japan blares the airplane scene in "Fight Club" - will a butterfly in America get knocked off it ass?

[1138]

No, I agree Lightivity. This meeting isn't for proving the quality of digital cables, per se.

This is more along the lines of Seamonkey (and others) claimg that they can hear differences between digital cables, when the cables are the only things (equipment wise) changing.

Seeing as how I (and others) feel that digital cable is digital cable, then in theory, their shouldn't be any differences in sound. And so the whole point of this meeting is to determine if their is any correlation between cable differences and any perceived sound difference.


And ultimately, as Enzian points out, their are other considerations we could take into account. And I agree. To me, even if there were slight differences in digital cables (and even with the ones present in analog), it's rather silly IMO to spend such extraordinary amounts on cables to "fix" those differences when there are these other aspects that are given no heed while probably playing more important roles.

Sound will be affected by humidty, air pressure, temperature, acoustics (which include physical layout, material, etc.), seating position, etc. etc. etc.

So to me, spending thousands of dollars on cables while not paying nearly as much attention (and money) on these other things seems like buying the best tires for your Ferrari and then putting low grade octance in the gas tank while you go driving over potholes.

[Lightivity]

So to me, spending thousands of dollars on cables while not paying nearly as much attention (and money) on these other things seems like buying the best tires for your Ferrari and then putting low grade octance in the gas tank while you go driving over potholes.

Well said.

[Enzian]

This is the The Official (and only) Optical vs. Coaxial Thread, right?

The only thing you change is the cable. You use the same equipment. Same brand DVD player, same reciever, same speakers. Give a listen. Change cables. Give another listen. Compare/contrast.
If you'd like, you can change equipment - but don't cross your expirements. If you change eqpt. you need to listen/compare with both cables, again.

And Taxi, while I agree with the spirit of your analogy, I would say spending tons of loot on cables at the expense of better eqpt. is like spending the farm on Mushkin memory for a x286. (yet another debate - Mushkin vs. generic DRAM)

[Dom]

And don't forget the double blind test... which, ultimately, also needs to include listening without a cable... I'm convinced that this, at least, will make for a distinct difference

[Wirehed]

Originally posted by Dom
And don't forget the double blind test... which, ultimately, also needs to include listening without a cable... I'm convinced that this, at least, will make for a distinct difference

indeed. Here I think we can all agree!

[Enzian]

[AirSickMoth]

Also, don't forget to do the good old fake out.

You go behind the reciver and pretend to change the cable... But you don't. You then ask people what the difference is. You say something grand like, "Now give THIS biotch a listen to."

When someone says it is better or worse.....

The test is over because it is too dependant on peoples own biased, influenced, inacurate, personal observations and not quantifiable, scientific fact.



1138, a different comparison for Cable and Cars would be:

Spending a fortune on Cables is like spending a fortune on Car Wax for your Ferrari. It might make it shinnier than the cheap stuff, but it doesn't make it perform better.

[Jellodyne]

The best analogy would be putting $800 hand crafted custom lugnuts on your Ferarri because it 'holds the wheels on better' than the factory lugnuts. They either hold the wheels on or they don't, though the expensive ones may impress your friends and neighbors.

As for the test, I suggest one test where you don't change the cable, but increase or decrease the volume slightly. I'd bet that would be a more significant change than the cable changes.

[Enzian]

Ooo! Jellodyne! Good call with the volume idea!

[PAceto]

If I may add my two cents at this late date, it seems most people are hung up on side issues. I've had a Master's in electrical engineering for over 25 years. I just finished designing a Gigabit router that had both optical (Sonet)and coax transmission. Believe me when I say that bits are bits regardless of whether they are sent over coax or optical cable. If you hear a difference in the sound quality, it is not due to the transmission mode (there are a lot of other things in the total path that have nothing to do with the transmission method). If there is a transmission quality issue that the error correction routine can't correct, the result will be either 1) silence or 2) very loud static (try listening to a data CD in an audio CD player to see what I mean). All other things being equal, I prefer optical cable for two reasons. First, there is no impedance matching problem. Second, there is no electrical connection between the two units eliminating the possibility of a ground loop.

[Enzian]

Halelujah and Amen, brother!

[Dom]

[PAceto]

For those who raised the issue of error detection and correction, I looked through the AC-3 spec (Dolby Digital 5.1) and found some answers. Each frame of data has two CRCs (cyclic redundancy check words). A CRC is like a checksum of the data in the frame, only more complex. This technique allows you to detect errors and correct most of them. There is also another correction scheme further down in the decoding that does some correction. The spec mentioned muting as a possible result of some types of errors. I looked for some mention of frame resend on error but I haven't found it yet. Here is a link to the spec for anyone who is interested: http://www.atsc.org/. Look for the AC-3 PDF near the top of the page.

[Wirehed]

snicker.

We'll see at the test.

[PAceto]

A listening test is purely subjective. Put a spectrum analyzer on it and you've got something.

[Chromy]

That's what I'm talking about Seamonkey says that a certain digital cable gives him more bass... Take a HTPC, or something else that can output a sine wave at on frequency, swap out the cables and measure SPL

Chromy

[PAceto]

Why not use the test tones on Avia? Rather than just give opinions, I've just decided to run some tests using instrumentation from work. I'll check the audio output at both the preamp out (using an RMS meter) and at the speakers (using an SPL meter). I think Avia has individual tones at a variey of frequencies. No more junk science!

[PAceto]

Well I ran the comparison tests last night. Unfortunataly, Avia only has frequency sweeps, not a series of individual tones. Fortunately, they were low frequency sweeps (most people claim to hear better bass on coax). I set up a sound level meter on a tripod at the sweet spot and I ran the front speaker sweep and the sub sweep over and over. At specific frequencies (as listed on the TV), I recorded the levels. I repeated the test with both optical and coax and found absolutely no difference. I also ran the pink noise tests since they were quick to do. Again, no difference between optical and coax. I only wish there were individual frequencies that stayed constant for a few seconds. It would have been a more rigorous test.

[Mr. Furious]

Did anyone create a test procedure yet? I'd be very curious to read it. How are you guys planning to manage the "Placebo effect"? Are you just planning to rule it out statistically?

[PAceto]

Using a sound level meter with test frequencies avoids the placebo effect. Meters don't have a preference.

[1138]

I thought it out some before but haven't given it much thought recently.

I was thinking of something like doing 10 listens in a row of the same clip, switching the cables for each listen. We'd figure out when to switch cables by flipping a coin ten times. Depending on time, I'd like to do maybe even more than 10 just to minimize sample size effects.

I'll think on this more. Anybody else have suggestions for specific procedure?

[Taxi]

Well, some of this we'll have to work out when we get there.

But basically, I was thinking it would go like this:

Everybody who is going to do the listening (ie pretty much everybody I think) sits in room A. Everybody gets pen and paper, with a list from 1-20 (or whatever) to write their answers down on. The person who runs the test plays a clip (10-20 seconds). Then, a pause (while cable is or isn't changed.) Then the clip again. Everybody writes down if they heard a difference, and whether they thought the first clip, or the second clip sounded better.

Repeat this several times. Some times a "better" cable is used the second time, sometimes first. Sometimes the cable isn't switched at all. Tests should be repeated enough times so that each cable is compared with every other cable at least once. (I will be bringing a Tice Audio digital interconnect, as well as Chromy's "monster" cable. ) Of course, all this cable switching is done behind some kind of blinder, or maybe even in another room, so that nobody can see what is going on.

Also, I think the clip should be changed after 2-3 listenings, so that nobody focuses on that one clip. (I don't know if that's scientifically sound reasoning or not.)

So, anyway, once all the tests are run, then everbody can be told what each test was (by number), and whether or not anybody could pick out the high-end cable.

How does that sound? (No pun intended.)