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Old 8th November 2012, 09:39 AM   #11
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Quote:
Originally Posted by HJWeedon View Post
Hello.

First we have to identify the customer. Is this going to replace cable? My answer would be NO. Copper cabling works pretty well. It is only when there are significant AC ground-loop problems that we have to do away with the copper connection.
I think it could be applied in a surprisingly large number of areas like for example in intercom and CCTV systems, all of those systems require to some extent the coverage of audio, but cabling is usually using copper/coax/ethernet, and therefore prone to lightning strikes.

Another possible avenue is the Pirate radio & HAM crowd (I don't condone what the former do but that doesn't mean you can't sell them a kit), they want to protect their source equipment, but they have to run coax cable to a tall antenna, or in the case of HAM's they want to send something an audio signal but they don't want to introduce ground loops or RF into whatever they are sending it to, so with the invention of a fiber replacement for RCA they could quite easily just run a length of TOSLINK down and power the transmitter from Solar at the top, and /never/ be worried about lightning strikes ever again. I doubt this crowd would be a very large customer though, maybe in the middle east or europe (france), yes.

Those would be the low cost end of the spectrum.

It is true that either end needs to be powered, however Solar is coming out in a big way, so that and the advancements in batteries pretty much make this a null and void issue.

The high cost end of the spectrum would of course be the expensive cable crowd and hopefully with a bit of good thinking we can beat the performance of 90% of these cables when it comes to the audio spectrum. (We couldn't beat copper on HF performance).

Where I think you guys need to concentrate on is inbetween there, what would get the average joe kind of people off of the analog RCA interconnect and over to fiber. Which is contradictory to what HJWeedon has said, and I'm sorry if I cause any offence.

We will probably have to do this eventually anyway, copper is getting more expensive every year, and how do we know its not the same quality as we used to have anymore? How do we know that its even copper? Shill out $30-$50 for a pair of RCA cables? or $10-$20 for a ALOSI kit?

Don't know about you guys but Lightning is a huge issue down here in Aus, at least it is where I live, and I like to unplug my equipment from the wall but if anyone has looked behind their audio equipment lately and seen just how close their RCA cables come near-to that power cable for your tv set should no doubt be worried about equipment damage from lightning jumping from your tv set or set top boxes antenna to your very expensive transport or DAC...

Most people don't really care about cable positioning, this would quell those fears, it would also allow the use of unearthed equipment with earthed stuff, and completely obliterate the ground loop issue WITHOUT having to go to digital.
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Last edited by freax; 8th November 2012 at 10:05 AM.
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Old 8th November 2012, 10:16 AM   #12
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Ontop of that, the garage band audio/studio crowd would apsolutley LOVE this idea.

Converting 1/4"/XLR to optical and back to 1/4"/XLR while remaining fully analog would sell like hotcakes.

Tho if a copper cable is cut it can be mended when out in the field, if a fiber one is cut it can't be mended, its gotta be replaced.
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Last edited by freax; 8th November 2012 at 10:39 AM.
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Old 8th November 2012, 10:47 AM   #13
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This could also solve the age-old folly of mixing analog signals in a noisy digital environment, say for example, oh I dunno, THE HOME COMPUTER.....

Imagine having your I2S bus coming directly from a PCI-E tap, then into your DAC which is located /inside of your computer/ and powered from battery.

Then using ALOSI it is then taken outside of your computer and into your amp/preamp....

And while you sleep, it recharges.
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Last edited by freax; 8th November 2012 at 11:04 AM.
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Old 8th November 2012, 07:15 PM   #14
dmills is offline dmills  United Kingdom
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Sorry still not seeing the advantages given the costs, simplest is usually best, and simplest is a bit of wire with appropriate interfaces at each end over the sorts of distances and channel counts hifi uses.

Large installations and outdoor events have gone to ethernet or fibre, but it usually carries a digital protocol (Cobranet, Dante, something like that), here the weight savings compared to a conventional analogue snake are compelling, as is the ease of producing things like broadcast splits.

BTW: The most linear FM discriminators are usually the PLL type which are essentially digital in some respects, for carting audio and control data over glass just digitize it already, it is no harder then this scheme and will almost certainly have better performance.

Cat 5 does actually make a perfectly usable cable for line level audio (4 pairs so you can send 4 channels trivially, and up to 7 channels if you are prepared to play it a bit clever (Look up 'phantom circuit).

The closed circuit guys are usually handling audio as a simple FM carrier, but they do not really care about quality which makes things easier.

It seems to me that all of this complexity is a band aid for kit with poor audio line receivers and drivers, far cheaper to put the fix in there then in some kind of powered 'wonder wire' which still has to connect via those sub standard interfaces.

There is probably much to be said for just moving audio as ethernet frames and converting only once you reach the final power amplifiers.

Regards, Dan.
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Old 9th November 2012, 12:20 AM   #15
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Gentlemen.

I have a really selfish reason for joining this discussion. I have an audio system of my own that does require about 120dB of dynamic range connection link. I presently use power amplifiers about 50feet (15meters) remote from the speakers. I am planning to use my Behringer Model DCX2496 Loudspeaker management system that my wife gave me for Christmas last year to drive 6 power amplifiers to Tri-Amp my K2 Klipsch Horns.

Since my Heathkit AP1800 preamp (modified for low noise performance, to be sure) is located so far away, I need to ship the Stereo Output to the Behringer without introducing noise and hum. The system is normally used at the 100mW level for normal listening, I can drive the Klipsch-Horns to the 50W level without distortion. That is a 27dB differential. Since the horns are 35% efficient I need a very low noise link at 27dB below full scale. 120dB - 27dB = 93dB, which is about the theoretical SNR of a 16 bit system.

Yo see, The reason is that I leave amplifiers and systems on all the time and when things are "turned off", I expect there to be no noise or hum to be heard when you put your ear to the speaker. Bumps and pops when other systems come on is OK.

Having worked professionally on 120dB dynamic range systems for over 35 years, I do not want to do worse in my home Audio system. I know it can be done, because I have done it in Medical CT scanners for years. ( I have some US patents on the technology)

I just want to tap the experience of you super critical guys to do a "design review" on my approach. My regular sea of engineers blank out when I talk to them about this sort of stuff. The "dynamic range" of run of the mill engineers stops at 17 bits, and blank out at 24 bits.

Thanks for your highly appreciated comments.

Hans J Weedon

Last edited by HJWeedon; 9th November 2012 at 12:29 AM. Reason: Corrections
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Old 12th November 2012, 10:33 AM   #16
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The Creative Science Centre - by Dr Jonathan P. Hare
THE LUXEON
http://www.modulatedlight.org/Modula...Amateur79.html


Quote:
CAUTION!, written in 1978: Simpler transmission systems, requiring less than, say, 50 KHz bandwidth, may use any readily modulated light source. Short range systems may employ light emitting diode sources which, except for the green or white phosphor-activated types, have a linear modulation characteristic, and are readily internally modulated at low voltages. Long range systems could use modulated high intensity gas discharge lamps, carbon arcs, gas lasers or solid state lasers. A coherent (ie. laser) light source is not mandatory, and may prove to be economically unjustified where bandwidth and limiting daylight is not a critical consideration.
Quote:
A resurgence of interest in optical communication came with the rapid advances in lasers and optoelectronics after 1960. In 1962, television signals were transmitted 18 miles using a modulated infra-red beam generated by a GaAs diode, prior to the general availability of the laser. The all-time distance record for terrestrial optical communication with speech modulation was set on 3-4 May 1963, when a 632.8 nanometer helium-neon laser beam was transmitted 118 miles by W6POP and W6QYY, from a point in the San Gabriel Mountains near Pasadena to Panamint ridge near Death Valley, California. An amplitude modulated 10-metre amateur radio transmitter was used for energising the laser.
http://www.modulatedlight.org/eos/Op..._Red_Line.html

Quote:
Initially, we had no idea how to do this, but after some experimentation we determined that applying RF to strips of foil properly placed on the outside of the tube did the job.
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Last edited by freax; 12th November 2012 at 10:55 AM.
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Old 12th November 2012, 11:17 AM   #17
DF96 is offline DF96  England
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I can't quite see the connection between experimental long-distance free-space optical communication (distortion maybe 10%, frequency response 300-3kHz, S/N 10dB?) and high quality audio interconnections. Modulating light is easy. Doing it to high quality is not.
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Old 12th November 2012, 11:25 AM   #18
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Originally Posted by DF96 View Post
I can't quite see the connection between experimental long-distance free-space optical communication (distortion maybe 10%, frequency response 300-3kHz, S/N 10dB?) and high quality audio interconnections. Modulating light is easy. Doing it to high quality is not.
Gee I dunno, they managed to put a TV signal over one... over 101km...

Click the image to open in full size.

Pretty good picture too.

http://www.darc.de/index.php?id=24358
Translation: http://translate.google.com/translat...p%3Fid%3D24358

Translated project page:
http://translate.google.com/translat....de%2Fdj1wf%2F

http://home.arcor.de/W_Fritz/Laser/B...BluRayeng.html
http://modulatedlight.org/optical_co...ideo_link.html
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Last edited by freax; 12th November 2012 at 11:52 AM.
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Old 12th November 2012, 12:07 PM   #19
DF96 is offline DF96  England
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Video needs bandwidth. Audio needs low distortion. Easy to swap one for the other using digital techniques; harder for analogue. A decent wideband FM discriminator can achieve about 0.5% distortion and 80dB S/N. It gets hard to do much better than this. Most people would want their interconnects to do considerably better than this.

Last edited by DF96; 12th November 2012 at 12:08 PM. Reason: add S/N
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Old 12th November 2012, 02:09 PM   #20
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I initially desired an AM modulation, feel free to brainstorm with that descision.

I can't see why we can't do a simple + to - inversion then convert V to I for driving a laser diode via current modulation, the voltage of the curve of a rising sinewave signal would be represented as a wide range of current modulation and the noise reduction would be the inversion of the signal, where quieter audio would be represented by a brighter laser diode and louder audio would be represented by a darker laser diode.

Surely there can't be that much noise on a TOSLINK /sealed/ plastic fiber?
There are other true-glass fiber optic cables out there too.

There would of course be range limits for representing a 1v p-p signal and testing to be done for a wide array of different laser diodes and resulting frequency response tests that need to be done, and resulting solutions to that problem.

A set of guidelines like for example the maximum length of a cable for a given desired/guaranteed noise level and signal level on the other side.

And it would have to be 1 channel per fiber optic cable.

Anyway I'm off to bed, have a good one.
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Last edited by freax; 12th November 2012 at 02:14 PM.
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