PETER ,You need to read my last message a bit closer as your response makes no sense, considering my statement. I don't know if you have been following this dialogue but my tests were done in a unbiased manner. I did much more than you suggest.

Martin, there's no need to get snippy. I did read your message closely, and I have followed this thread from the beginning.

It's also rather difficult for me to respond to your claim that "[my] response makes no sense, considering [your] statement" when you don't tell me what statement I failed to consider.

If you read MY message more closely, you'll find that I did not accuse you of being a biased person. What I was attempting to explain to you was how the placebo effect could apply to you.

In general, people who are affected by placebos are not foolish, gullible people. In the medical realm, there is an amazing symbiosis between the mind and the body. Therefore, in some cases, when the mind thinks the body is receiving effective medical treatment, the treatment actually is effective. (In the case of pills, the placebo is usually sugar. It has no intrinsic medical effect.) In short, because they think the pill will work, it does work, in a very real sense.

Correspondingly, if you go into a test thinking you're going to hear a difference, you will hear a difference. By that token, if I went into a test of optical vs. coaxial cables, I would probably not hear any difference (even if there is!). Whether or not I listen in an "unbiased manner" as you put it, my predisposition _will_ effect my perception.

And the reason I can confidently say (despite your objections) that you _did_ have expectations which _did_ affect your perception is that nobody is immune from this unconscious bias. (I don't doubt that you went in without conscious expectations, but everyone has unconcious expectations.) In the same way a medical patient think he is unbiased in assessing the effectiveness of the treatment, we think we are unbiased in our assessment of the world around us. But we're not. That's why medical tests still use placebos.

So, what I suggested was trying a simple test to illustrate this effect. Have somebody tell you they're using a coaxial cable when they're using an optical cable. In effect, the cable is a placebo. You think it's a coax, but it's really an optical. If it still sounds like a coax to you, then the perceived difference comes from your expectations.

Of course you can't be aware that the cable is just a placebo.

If you actually performed a methodical test, including double-blind tests, checking for the placebo effect, etc., then I apologize for belaboring the obvious, and I'd be curious to know precisely how you performed the test.

If not, don't tell me I'm speaking nonse.

Er, that should have read "nonsense."

[Removing foot from mouth now.]

Peter ,I didn't mean to sound "snippy". I misunderstood your meaning of "looking" for a difference".The tests were done with 4 brands of interconnects of both optical and coax (of each brand) in both stereo and 5.1 channels, ranging in price from $1-200. I was able to A-B both types without any knowledge of which cable I was listening to. The switching was done by a third person who kept notes. I did this first alone and then with three other people. One was a audio engineer, one a professional musician, and the third an "average" person" with no particular audio interests. All parties picked the same two cables as their choice. One cost $100,the other $130. This procedure clearly could not follow the scientific method and has many possible flaws, but it was about as unbiased as people can get under the the circumstances.To my surprise these results were very similar to the subsequent Home Theater article mentioned earlier.This was repeated 2X with similar results.

Interesting. Thank you for describing your test in more detail.

Did this third person who switched cables ever fake switching the cables? Did he mix up the order in which he tested them?

I'm trying to understand precisely what you mean by A-B. Were you asked to (and could) hear a difference between the two cables, or could you consistently identify which was which, even when the tester tried to trick you?

In the former case, the power of suggestion (i.e. "these two cables are different") which can induce the placebo effect.

Also, did you perform this test with 5.1 and stereo separately, or did you listen to both formats each time you listened to a cable?

The reason I ask is that, as shown by the coat-hanger-as-a-cable article, 5.1 is a specially encoded format in which subtle timing issues (i.e. jitter) will have no effect. It's like an MP3: it receives the raw data, from which it generates the audio with its own clock. In contrast, PCM is just the straight bits, decoded as a real-time signal. (I.e. A delay in transmission between two bits could change the represented waveform very slightly, assuming the receiver is deriving its clock from the incoming signal.)

Peter,
The clock is derived at the receiver using a circuit called a phase-locked loop. You mention delays in the signal, but noise and reflections cause problems as well. As I've said before, it would be nice to see a comparison that used test equipment to monitor for these errors.
Doug

One test was done randomly with no knowledge of what type, or which brand was being auditioned. One test was done as a coax vs. optical showdown. In stereo one cable was preffered by all. In 5.1
there was no clear winner. In the face-off coax
won every time in stereo but in 5.1 no clear differences were heard, except strangely enough all listeners preferred one of the 8 cables. In
the face-off we were not told whether it was coax or optical.

Sorry to keep hammering at this, but I'm still curious.

You said 8 cables were tested, and everyone preferred one of the eight. Was the order in which they were presented to each person the same? Did the listeners know there were 8 different cables?

Ideally you want the order randomized (in case there's some tendency to pick the nth cable). Likewise, you don't want to know how many different cables there are. There may be 1, there may be 10. You should hear at least (2 x cables) tests, some of which involve no change in the cable. You may need even more tests for a statistically significant test; I'm not a statistician.

The tests were completely at random with the "switcher" doing his best to fool us in every concievable way.The coax v. optical was random also, but we knew that we were comparing coax to optical, just not which cable we were hearing.
In 5.1 we couldn"t hear enough of a difference
to claim one type was superior but, one cable did sound "smoother", "richer" etc.

OK, I've heard enough. If you would like to compare the PHYSICAL differences of coax to optical, I'm on board 100%. Sonically, there is no difference.

I will put my money where my mouth is. If Martin and his friends (those who participated in the test, and can accoridng to him, HEAR the difference between the two types of cables,) would like....I will create a testing environment for them to prove me (and science) wrong. Respond by email, let me know that you are serious, and I will prepare a lab where ALL of the tests will be SCIENTIFIC. I will hire outside parties and statisticians to create test which are statistically significant and have the lowest possible (within reason) chance of producing "random" results.

If Martin is serious, I will pay $1000 per person who can (accoridng to the testing procedure) tell the difference. All that I require is that if they can not (statistically significantly), the TOTAL of my expenses will be reimbursed.

Carl

Carl, I have no doubt as to your ability to think intelligently but this has all gotten a little out of hand. It seems that many people, some respected professionals have heard differences that are consistant from test to test. Why this is so is debateable. Frankly, I don't care that much. If
I get two cables, one coax, one optical from the same manufacturer and I consistantly choose the coax cable when doing a blindfolded A-B test, that's good enough for me.
I hope you have gained as much enjoyment from this dialogue and your home theater as I have. Good luck and bye for now.

Carl,

It would be interesting if you proposed your challenge to the folks at Home Theater Mag. Maybe we could get to the bottom of this issue once and for all.

One of their quotes - "I was shocked, though, to hear how much of a difference some of these cables made when we were listening to PCM stereo from CDs. These are differences anyone—even a nonaudiophile like David—can hear."

Interesting thread, good luck Carl.

DougW

The Optical cable is better because nothing can travel faster than light. I have even noticed that the sound in my HT system arrives to the speakers before the picture shows up. I had to put a 2k ohm restor on the cable to keep the sound in sync with the picture...

modern film audio "arrives" a half frame before the visual to have the sound arrive about 40 ft into the theater to compensate for the speed of sound as to the speed of light. The difference between optical versus coax is probably not measureable to to the shortness of the cable relative to the total system. Modern surround processors can time delay audio for HT for this reson. Sorry but a 2k ohm is no substitute for time delay. This will only degrade the sound at certain frequencies but your on the right track for noticing the difference in arrival times. Very perceptive.