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In Reply to: Harmonic Tech Cyberlight --shocking measurements posted by Jon L on March 9, 2005 at 09:46:10:
Fiber optics technology is purely digital (light on/off). But apparently Harmonic Tech Cyberlight is trying to use it in analog application by varying the intensity of light (They have laser tx/rx modules inside the terminations that convert electrical signals to a continuously-variable intensity laser beam).Thus the distortion, and "Roller Coasters" like frequency response :)
Follow Ups:
When I need 300m interconnects, then I'll consider optical transmission. But as a replacement for conventional audio ICs, no thank you. I've put too much effort into minimizing the number of components in my signal path to even think about these things.I can't imagine anybody wanting to introduce two more _active_ components into the chain, especially ones that do electro-optical conversion. And especially people with systems at a performance level where they're worried about crimping vs. soldering, Bullet vs. Nextgen, etc.
Dave
I have never seen or measured these cables -- nor have I seen measurements posted.However, the technology seems to me to be something you would use for long distance transmission, not a short interconnect. As Dave says, you are adding two extra stages of electronics into the system.
I do have a Ph.D. in opto-electronic devices, and I can imagine whipping up a design for such a cable. I'm sure it could do an "okay" job, but I can think of a number of "gotchas" already.
First, both laser and LEDs are nonlinear output vs. input. LEDs tend to drop off a bit with current, and sometimes have a slight turn-on threshold of a few millivolts (usually because of non-ohmic contacts or some non-radiative recombination). Lasers have a turn-on threshold that is not constant with temperature, and their output past threshold is more non-linear than LEDs. This means that they need feedback to operate without severe harmonic distortions.
The feedback on a laser module is often a silicon photodetector measuring light coming out of the back laser facet. This does a pretty good job, but not perfect. The detected light does not always exactly correspond to the light getting coupled to the fiber, as the exact beam shape changes slightly with output intensity.
A solution is to use the feedback from the fiber itself -- by using a splitter. You would want to do mode stripping of the cladding first, to make sure you are getting light just through the fiber core.
The feedback detector could theoretically have nonlinearity, but you can get pretty linear ones these days -- providing you don't use too high an optical signal.
The detector circuit is just done with a high quality reverse-biased photodetector. Running it in photovoltaic mode would be too slow, and likely less linear.
This would be the way to go for long distance signals! In fact, the battery power is definitely the way to go. I always used battery power for my high-sensitivity photodectors. It reduces noise considerably.
However, it would be very easy to get high amounts of harmonic distortion if these cables are not done right. I would be very interested in seeing distortion figures. That would be the proof needed to determine if this was a technology that made sense. If the harmonic distortion is low, then they could have a winner. The rest of the sound quality lies in the electronics at each end.
Neil
> When I need 300m interconnects, then I'll consider optical transmission.Up to 200m actually.
> But as a replacement for conventional audio ICs, no thank you. I've put too much effort into minimizing the number of components in my signal path to even think about these things.
I hear you, but you're approaching it from the traditional cable perspective, which I think validates Jim Wang's approach, in fact.
Given the many ways environmental interference, not to mention radiation, especially digital, emanating from your own system, can pollute the signal, especially in the weakest part of the chain, the cables, it's no wonder the less-is-more approach has become SOP for some. I know, I've been there.
In my experience, everything in fine audio is about balance. What if you =could= eliminate major entry points for RFI/EMI, and all the rest of the dreck floating around us. The Cyber does that. Completely with the battery pack, and "mostly" with the wall-warts that are, after all, meant to be used as backups while the battery charges. With the 'warts, there's only a slim chance of any ground noise entering the system since of course the 'wart is grounded for safe operation. And as has been stated, there is suppression built in. The cables, in any case, are meant to be used on the Power Pack.
Eliminating that major source of pollution might well be worth going active even though it adds rather than subtracts components. On balance, it might we worth it. You have to consider that you tuned your system around current technology, but that newer technology might free you to experience better sound, the final proof in the pudding, no?
> I can't imagine anybody wanting to introduce two more _active_ components into the chain, especially ones that do electro-optical conversion.
Especially? Why is that?
> And especially people with systems at a performance level where they're worried about crimping vs. soldering, Bullet vs. Nextgen, etc.
But systems like that are the ones who benefit the most from lack of interference. I just think it's better to remain open-minded about it rather than slaming the door to possible relief from long-standing cable problems.
Regards,
Jonathan
Dave
From what I can see a set of Jensen audio isolators for 120.00 from Markertek gives you isolation, RFI rejection, no wall warts, near flat frequency response, lower distortion,(if that's still an issue)and for less money than these cables from what I understand. Of course it doesn't have the inconvience that most audiophiles truly desire.
d.b.
> for less money than these cables from what I understand.Ah, but how do they sound?
You know, like when Larry "The Buzzard" King leans into his mic and grates out "Howww does it feeeeeel..."
> Of course it doesn't have the inconvience that most audiophiles truly desire.You forgot the badaboom!
Regards,
Jonathan
From what I can tell from your reply or lack there of as the case maybe, I'll stick with the transformers. They don't have much of a "sound" when used properly, and for some of us; that's the approach we are looking for.
The Ever Evil Doctor Steel
> From what I can tell from your reply or lack there ofWell, I... don't know what you expected, Dan. "Xformers are bad because..." or "Cyber is better because..."
I've talked about the operation of the cables when others have misunderstood, and tried to make their advantages clear. I don't feel like it's right for me to fill up a message lauding their sound and will the reviews on PFO, and upcoming in Stereophile and 6moons speak to that. I know Tim de P's work, I've listened to his xformer-coupled components, and they were totally terrific. I used the Expressive step-up for a long while, and can appreciate xformers for what they are and how they can be made to perform.
This is something else, another approach to the problem. Maybe they'll sound the same as xformers, and if so, the xformers would be the way to go, obviously. But if you compare the two and the Cyber seduces you way beyond what you thought possible, then it's worth the extra money for those who feel they prefer it.
> I'll stick with the transformers. They don't have much of a "sound" when used properly,
C'mon, you're stretching my words to fit your attitude, Dan. Clearly I'm not saying the CyberLights have a "sound" in the sense you're using. In fact, quite the opposite, having disposed of major sources of interference in the signal.
There are some adjustments to make, of course, like hearing the upper ranges without a scrim of noise making the sound edgy, and that goes for the entire frequency range. That promotes a kind of continuousness (for want of a better word) that also allows the lister to relax into the music. But I'll let the reviewers speak to that.
> and for some of us; that's the approach we are looking for.
And more power to you. Diversity fuels the engine, it's all good. What's not so cool is short-sheeting a new technology saying that one can achieve the same sound for 120 bucks. How do you know that?
> The Ever Evil Doctor Steel
The Doctor Is In!!!
(-"
Jonathan
"What's not so cool is short-sheeting a new technology saying that one can achieve the same sound for 120 bucks. How do you know that?"If you have data on frequency response, phase, noise, and distortion then please tell me where I can find it so I and others can make a rational decision. Jensen is kind enough to do that so I would expect the same from you.
The Ever Evil Doctor Steel
.. until you read the info or look up the facts.First, the graph published at the individuals web site was not for an HT product, but for one he "thought" was the same as the HT product.
Second, they are not using digital modulation or encoding techniques, but rather, analog light transmision via photoreceptors. As a simple example, varying the light level from an LED in response to the analog signal strength, and feeding that into a photcell with a DC bias across it, is a similar kind of technique.
As for the roller coaster frequency response, I don't suppose you noticed that it was on a scale of tenth's of a dB for the major divisions, and the total deviation from approx. 40-50 Hz on up to around 100 kHz was about +/- 0.1 dB. Not exactly what most folks would call a roller coaster FR, in fact, many CD players and electronics like preamps and power amps have comparable frequency response deviations, or even greater. Most modern HT receivers vary this much OR MORE.
So don't let your ignorance and bias affect your evaluation of such a technology, and please find out the true facts before posting your misunderstandings as fact.
What ever happened to the pursuit of "Science" ? This kind of post sure isn't it.
Jon Risch
Wow jon...you must really hate Tony...why else would you call him ignorant and biased??..JR: ""Please refrain from comments..... until you read the info or look up the facts.....So don't let your ignorance and bias affect your evaluation of such a technology, and please find out the true facts before posting your misunderstandings as fact.""
Hmmm...lets see...Jon L said this:
Found the following measurements of Harmonic Tech Cyberlight on the web. I still can't believe my eyes about the frequency response graph :(""
To which, Tony said this:
Fiber optics technology is purely digital (light on/off). But apparently Harmonic Tech Cyberlight is trying to use it in analog application by varying the intensity of light (They have laser tx/rx modules inside the terminations that convert electrical signals to a continuously-variable intensity laser beam). Thus the distortion, and "Roller Coasters" like frequency response :)""
And then, you say this:
First, the graph published at the individuals web site was not for an HT product, but for one he "thought" was the same as the HT product.
Ok, that is a good clarification....Then you said this:
Second, they are not using digital modulation or encoding techniques, but rather, analog light transmision via photoreceptors. As a simple example, varying the light level from an LED in response to the analog signal strength, and feeding that into a photcell with a DC bias across it, is a similar kind of technique.
Which, of course, is exactly what Tony said here....
""trying to use it in analog application by varying the intensity of light ""JR: ""What ever happened to the pursuit of "Science" ? This kind of post sure isn't it.""
Whatever happened to impartial and unbiased moderation, and civil discourse?? It would appear that "Tony bashing" is your idea of civility?Please leave your agenda elsewhere, Jon..there is no need to bash others. Simply correcting their errors would be just fine..
Cheers, John
I have told Jon in the past that if he takes a usual detour off the subject, his post will be ignored....no response.Thanks John :)
Knowing what you are talking about helps a lot, and posting ignorance and heresay, instead of looking it up or reading about the subject, always helps too.When you post these ignorant and uninformed posts, posting as if you were the one on the right track, and everyone else is off in left field, it helps no one, including you.
However, it may confuse a newbie or neophyte, hence the need to either setr the reocrd straight, or delete the posts. I have been choosing not to delete, leaving your uninformed reply up for posterity.
Jon Risch
> Fiber optics technology is purely digital (light on/off).From all that I understand, as Dan Rather might say, you're standing in a puddle with a power line in your pocket and a frog in your sock. It's very clear; CyberLight makes use of =photon modulated= signal transmission. There's just no on/off about it.
> But apparently Harmonic Tech Cyberlight is trying to use it
"Is" using it...
> in analog application by varying the intensity of light (They have laser tx/rx modules inside the terminations that convert electrical signals to a continuously-variable intensity laser beam).
Correct, as used in the telecom industry.
> Thus the distortion, and "Roller Coasters" like frequency response :)
You're a riot Alice! No distortion or roller coaster FR anywhere that I can hear, or others, who will report their finding soon in major reviews.
The measurements were bogus and incorrect.
Think positive.
Regards,
Jonathan
No matter how well the cable transmits the modulated light, the signal still has to be converted at both ends, and the conversion electronics are as susceptible to obvious and nonobvious design problems as any other bit of audio electronics. The little boxes are fed with wallwarts and humdrum wire, so RF pollution is a strong possibility.
> The little boxes are fed with wallwarts and humdrum wire, so RF pollution is a strong possibility.Nein.
Jonathan
I heard them in my system and liked them enough to buy em!
If they only really work well with fully-charged batteries, then it seems petty to sell them with the AC supplies and charge extra for the battery packs.
What good will it do to have advantage of optical cabling (such as immunity to noise) if the source-which in this case is the light transmitter module-is putting out crappy signal.And as you said, having wallwarts and humdrum wire feeding these modules doesn't help the situation either :)
> What good will it do to have advantage of optical cabling (such as immunity to noise) if the source-which in this case is the light transmitter module-is putting out crappy signal.You really do jump to conclusions. "Faster than a mugwamp on speed." It's not a crappy signal, it is not polluted, the only place where ground is connected is at the receiving rx, but only on the wall-warts. There is zero interference when using the battery, and the 'warts are only for backup purposes while charging a down battery.
> And as you said, having wallwarts and humdrum wire feeding these modules doesn't help the situation either :)
C'mon, ask, don't tell.
How can you speak with authority when you're just guessing?
As I've said, the measurements were bogus and should not be taken into consideration.
Regards,
Jonathan
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