Has anyone out there used fiber optics between amps and head unit? Are there any head and amp units that have direct fiber optic inputs? I know there are studio/home units, but car units?

Just thinking this morning about if I place my amps in the rear area, then running a monster thick power cable to the front head unit, why not fiber optics instead. It's micro thin and carries any power and frequency car audio would use.

With the 12V jack in the back, use it for a RCA to FX TX converter. Then use the 12V jack in front for the FX to RCA RCV converter. The converters are small ( 3.5" x 2" x .5" ) and use 12V. It would only require a TX to RCV unidirectional setup.

Feedback anyone?

 

Personally, I don't know of any aftermarket headunit or amp that uses fiber optic cabling. However, I do know that Mercedes has been using fiber optic radio systems in their cars since, at least, the 2000 model year. Our E-Class Mercedes has the fiber optic system. It's not really the big advantage you would think because it's nearly impossible to get aftermarket stuff for it. For example, I would like to add a CD changer, but MB charges something like $800+ for theirs and no one else makes one because of the fiber optics.

Roundy

 

>>Personally, I don't know of any aftermarket headunit or amp that uses fiber optic cabling. However, I do know that Mercedes has been using fiber optic radio systems in their cars since, at least, the 2000 model year. Our E-Class Mercedes has the fiber optic system. It's not really the big advantage you would think because it's nearly impossible to get aftermarket stuff for it. For example, I would like to add a CD changer, but MB charges something like $800+ for theirs and no one else makes one because of the fiber optics.
>>
>>Roundy

Roundy,
Only the power input from the amp to the head unit would use the fiber.
Any other component would connect using conventional method. If MB is charging 800+ they're ripping the consumer off, but what's new.

 

My understanding of fiber-optics is that it is a method of transmiting light though a very transparent yet flexible cable. Some audio manufacturers use fiber-optic cables to transmit digital signals by using D/A converters (digital to analog converters) to change the signal from a pulsing electical current to a series of light bits, and then back again at it's destination. The reason for doing this is to keep any induced noise from getting into the signal along the length of it's route. To my knowledge there are no truly digital signal amplifiers currently available for car audio applications. So there's no way to build a system that has a totally digital signal path. Many aftermarket manufacturers use fiber optic cables to connect digital signal from their CD changers to the head unit at the front of the car. This elliminates any chance of noise being picked up by those cables. It is possible that we will see truly digital amplifiers for car audio in the future. When that happens it will make way too much sense to build a totally digital signal path audio system. I expect though it would be very expensive to build a system like that right now.
Good luck,
DV

 

>>Feedback anyone?

O.K. - first let's back up.

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Sampling:
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No "power" is transmitted through fiber - fiber is solely a light conduit for raw digitalk data. The amount of bandwidth available on the fiber is based on how often the digital signal has the ability to change it's signal from 1 to 0 or from 0 to 1.

On legacy CD player (i.e. all existing consumer CD players prior to the introduction of DVD audio) the clock cycle is roughly 44kHz. New DVD Audio is capable of up to 96kHz sampling rates.

Basically, legacy CDs use Cross-Reed Solomon encoding which assumes people can hear from roughly 20Hz to 22kHz and to sound "non-digital" you would need to be able to have two samples of any given frequency - so, you end up with the high end of the human hearing range of 22kHz times 2 for the number of samples you need to faithfully reproduce that frequency for anyone but the most **** audiophile.

MiniDisc (MD) audio uses "phyco-acoustic" mapping (no, really - this is what Sony calls it!) of audio to have a variable samping rate to allow for compression of the data it needs to store. Basically, there are some commbinations of sound that our ear can't hear the difference between - as a result the MD algorithm (at least since v5 of the spec or so) just stores the verswion of the sound that takes up the least space on the MD.

DVD Audio uses a different encoding and assumes you need a higher resolution of sampling to faithfully reproduce frequencies... supposssedly sounding that much better than legacy CD. Yep - that means it's time for everyone to buy the White Album yet again on another format. :smile:

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Fiber, what is it, why you want it:
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It's a pathway that allows you to transmit the digital data using light (for simplicity think of 1=light on, 0= light off) with zero (o.k. - close to zero) loss of information from source to target.

Awesome - zero loss from source to target... big deal... at the end of the day you still need to have that signalk converted into analog. Then you need that analog signal ampliphied and that ampliphied signal fed to an actual air mover (speaker).

This piece of conversion from digital to analog, the amplification, the signal path from amp to speaker, and the actual speakers are where you can spend some serious hard-core money. I'm well into the 5 figures approaching 6 on what I've spent on home audio.

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Back to the source of the thread:
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Has anyone done this in a car?

Yes, oh yes, oh yes.

There are a couple folks out there who do custom work - you can drom $20k on a system from them. Or you can go for a retail setup - McIntosh Head Unit is one of the units available out there.

There are other retial companies that sell this quality of car audio but you won't find one cheap.

IMHO - fiber in the car is completely overkill - esp. in a commodity car like the MINI. You don't have the sound isolation to support this system. Even in a Bentley with another 200 lbs of sound deadening material applied internal to all areas of the car + the armor package giving you 1/2" dual paned windows you MIGHT be able to tell the difference in sound quality... if you're sitting still with the engiine off.

While I love audio.... a car is a hostile environment for audio. Save your audio money for a more controlled home environment or buy more CDs, errrr.... I meant DVD Audio Discs.

-Dave Quick

p.s. This is all from a home enthusiast point of view - I haven't looked but I'll bet howstuffworks.com has better explinations. Heck, I could have gotten stuff wrong in here - you should not live the rest of your life thinking this is the X-files style Truth with a capital T.

p.p.s. My 2001 Mercedes C-240 DID use fiber between CD and head unit - and it all the interconnects on the car in fiber. Yes, it was flakey. Mercedes blaimed their suppliers. I blamed Merecedes. Mercedes C-240 traded in on 2002 BMW 525i... no fiber, no problems. :smile:

 

Thanks for the clarification. You're obviously more knowledgable on this topic than I. Bottom line...fiber optics is not an advantage for the average car audio enthusiast, on that I think we both agree. Good luck with your new Cooper S! I've had mine for about 3 months and over 5000 miles, and it's a great car.
Thanks,
DV

 

Oh well you can not convince some people that power is or say transmitted over light waves.
What is a radiation beam converted from fiber optic? Oh yes converters are involved, but the transmission is fiber optic. Fiber optic will and does transfer power.

I’ve been working in the field of fiber too long not to know these things.

 

So why did you start this thread in the first place, Mr. Smarty-Pants?

 

And if you use thin fiber-optic cable to transfer the *power* for the amplifiers, instead of thick copper wire, doesn't that mean you'll still need a big honkin' power supply at the source end of the fiber-optic cable?

I understand using fiber-optic for audio signal/data transmission, but how exactly do you use fiber to supply 500 watts to an amplifier?

 

Get a degree in physics if you wish to know the way it works. Why should I explain anything to you about how it does. I’m not holding a class here.

 

Because it was a thought at that time it would be a great way to do it Clo, but the cost may not allways make cents.

 

Well, my undergraduate degree is in engineering, with a bit of physics, and I'm currently working on my Master's in Applied Physics (and doing quite well), so cut me a little bit of slack, okay? Unfortunately, I haven't had any classes yet that go much beyond the basics of fiber optics.

I'm fully-aware that fiber-optic cabling can transfer power, but there's a big difference between using fiber to redirect a 100 milliwatt medical laser and throwing half a kilowatt down a fiber cable to power an amplifier and trying to get some useful mechanical work out of it at the other end. I'm trying to find out more about the available fiber out there, but unless you want the cable to be the size of a garden hose, I'm not seeing too many options that can both handle the required power density *and* can scale up to kilowatt levels.

And why would you want to use fiber to power the amplifier, anyway? You're not getting that much transmission loss with regular copper, and since you're not worried about having to preserve an audio waveform, you can clean up any induced EMI with filters at the downstream end.

 

Sony had a complete digital system back in '95. Fiber between all components, though the amps were conventional. Even a full digital amp needs normal 12V power. Heck, if you want to talk about telco fiber equipment, even the repeaters (amplifiers) use conventional power. Not sure what this notion is over transmitting power over fiber. Fiber = light...the light is used for signaling, not power transmission

 

Exactly, which is why I'm puzzled about sndwave's claim that Mercedes uses a fiber connection to *power* the CD changers in their cars. Using it for signal connections I can understand, but not for power transmission.

Light, like any form of energy, *can* be converted into useful mechanical work, but if you look at trying to use it to transfer more than a few milliwatts *and* turn that power into electricity at the destination, it falls well short of practicality.

You *could* put a 1,000-watt laser at one end of a thick-*** fiber optic cable, and a few hundred optical-to-electical converters at the other end, but the converters are only about 50% efficient if you're lucky, and then there's the problem of finding/buying/installing/cooling a kilowatt laser to use as a source in the first place. Plus, with a power density that high, the first time you bump, kink, or look crosswise at the cable, you're liable to melt the fiber. At best, it'll stop working, and at worst, you're going to reflect a significant amount of the power right back at the source.

Meanwhile, to transmit the same amount of power with copper, all you have to do is go down to Radio Shack and get some 1/0 power cable and you're done.

 

Sony CD changers used a control cable call a 'Unilink' cable, or umbilical, plus RCA's for signal. The Sony digital system used fiber to the CD changer (a toslink IIRC), but still needed the unilink for control and power. Alpine uses ai-net....same deal but all combined in one copper cable.

As for Mercedes running a changer 100% on fiber, there may be a single cable with fiber in it, but it's got copper in it to run 12V. I'd put $$ on it.