[semi-ot] why isn't audio digital?

[jackohat]

I read over this board a bit, and thought maybee someone at polk could shed some light on it, but how come although most of the signal people send to their amplifiers comes from a digital source, there is no such thing as a digital interconnect? There is in the home audio world(optical is digital i believe, although i dont understand why they decided on optical, as opposed to using wire like the rest of the world does to send a digital signal)

People spend so much money(especially in home audio) for quality audio(and video) interconnects, but since most everything(cd, dvd, and satelite radio, although not normal radio) is digital at the source, why isn't it sent digitally to the amplifiers to prevent signal loss?

If we can send 10mbit/s over 4 pairs of relatively cheap copper wire in a computer, using cards that cost $10 or less(after packaging, shipping, and profit for the retailers) surely the same could be done for audio? CD quality sound is arround 700kbit/s, (even a 96kHz 32bit signal is only 3mbit/s) and then you would have the guarantee that the signal getting to the amplifier is exactly the same as that coming from the CD(i think there would be plenty of bandwidth, and short enough latency to resend something with a bad CRC, theres enough bandwidth you could just send each piece of data multiple times so that the equipment doesn't actually have to talk to eachother, just one send, the other receive and check CRC's or whatnot)

Obviously its not incredibly simple, but it doesn't seem all that hard either.

Jack-o-Hat

Oh - I put this semi-ot because i know polk doesn't make receivers or interconnects, but i figured being part of the home/car audio world someone arround here might have some clues.

[phuz]

There is a such thing as a digital interconnect. As you said, optical tosling cables are digital. Digital coax are the copper digital cables that you were wondering about.

The reason to chose optical over copper is that light is not as vulnerable to interference as copper is. Overall you tend to get a cleaner more pure signal with fiber than you do copper. This is why most data systems and large networks (think phone, internet, broadband) are all 'upgrading' to fiber.

Why isn't it sent digitaly to the amp? At some point the signal absolutely MUST be converted to an analog signal. Speakers aren't digital, and I don't forsee someone trying to make digital speakers anytime soon. ;)

So somewhere along the signal path the signal has to be converted to analog. The reason that it is usually done in the receiver or source component is most likely for convinience of design and simplicity, as well as sound quality. I wouldn't want my DACs sitting right next to a huge power supply and high current amplifiers.

For more answers, you'd have to ask an EE. There are a few around here somewhere, my answers were just based on logic. ;)

[Jstas]

You answers are 100% correct phuz.

Speakers are analog because your ears are analog. Your brain doesn't have a D/A converter either so your sound source for your ears has to be analog.

D/A converters are placed in the head unit or the CD player or what have you because of intereference and different FCC regulations concerning automotive appications.

Another important factor is that you are running on 12v DC and not 120v or 240v AC. That makes a difference in how far you can send a signal before degredation becomes too great for the error checking software in the signal processor to fill in the gaps. Sending an analog signal is easier because you don't have to have an incredibly high sampling bit rate for the digital signal to make up for not only signal degredation but also noise and intereference. It's easier to localize and clean up intereference in an analog signal too. Most car stereos are expensive because of the miniaturized components they must use. They have to fit within a certain space so adding a high bit-rate D/A converter to either the head unit or the amplifier would not only double cost but probably double the amount of space used.

Now, there are digital automotive amplifiers. They used to require special head units that were nothing more than a pre-amp/tuner and even then, they had to have a seperate box that contained teh actual pre-amp and the signal switcher. They are prohibitivly expensive for most people though. Also, due to the electronically hostile automotive environment, they don't offer much better sound than you high end analog stuff which is substatially cheaper. Alot of companies are creating automotive theater systems now but they still contain the necessary digital electronics in either digital devices like teh CD palyer and the DVD player and pipe and analog signal to the automotive amplifiers.

Car environments are extremely noisy and down right abusive to electronics. That's why all the important stuff like your enging management system is grounded out the wazoo and sits in sheilded, weather tight boxes.

While the goal in both home and automotive audio is the same, the path you have to take for each goal runs off in opposite directions. Basically, apples to oranges.

To really understand how all this works and not just go on somebody telling you that the laws of physics say so, learning something about basic circuits will shed alot more light on it than a few posts in an internet forum.

[George Grand]

Fireball John,

Drop me an e-mail at:

njgrand@bellatlantic.net or the real good e-mail address for me that I gave you. I have something you might be interested in, or could at least help me out with your car audio knowledge.

George

[PoweredByDodge]

i know i'm not answering the question but this aside may be helpful -----

there ARE some very very very very good interconnects for preamp inputs / connections out there... so good that you would be happy enough with them that you probably would nto care about whether it was digital, analog, or otherwise -- like Jstas said, the bgi problem with the car is its 12 votls not 110 / 220 so you get signal degredation... the best way around that is to get a high power deck (or linedriver) that'll put out at least 4 v true rms (most 4 v decks are actually 2.2 volts or so) ... run that true 4v line through some high end cables and you'll get no hiss, no noise, nothing but good sound.

Streetwires Zero Noise 5.0 (now since discontinued) used to be my brand of my choice .. still are when i can find them... beyond braided technology they're also shielded and have an inductor coil in each connector so as to filter out as much interference as humanly possible.

Monster cable makes some good ones too... Swiss ... Stinger... there are many other - FAR BETTER - ones out there -- i just am not that well versed in brands.

[automaticman]

The old Pioneer ODR system and their newer dex/deq-p9 uses fiber optic interconnects. Expensive stuff though.

[Jstas]

Originally posted by PoweredByDodge
Streetwires Zero Noise 5.0 (now since discontinued) used to be my brand of my choice .. still are when i can find them... beyond braided technology they're also shielded and have an inductor coil in each connector so as to filter out as much interference as possible.

You can still get the Zero Noise 5.0 wires along with the Zero Noise 3.5 wires. The new stuff is the Zero Noise 2, 3 and 6 wires. I have the Zero Noise 6 wires and have had no troubles with them at all.

[PoweredByDodge]

"""You can still get the Zero Noise 5.0 wires along with the Zero Noise 3.5 wires"""

Where? -- I could use two three foot lines of the 5.0... (see my grief below).


Far as the 2/3/6 being new -- yup... but i had been told they were the "replacement" not an "addition" to the line(not sure eitehr way - but all u find in teh stores are the 2/3/6) ... and the 6.0's are nice, but they're more like the 3.5 than the 5.0... mitek guy told me they got rid of the ind. coil in the terminals and instead of having like two separate wire jackets that aare "stuck" together in the middle (like speaker wire - so if u wanna separate them you just pull them apart and voila u got two wires) they instead are singel jacket, where both left and right wires are run through the same plastic shell and you can't pull the buggers apart.

i bought two lines of 6.0 -- they just seemed too thin... too "chinsey" -- the 5.0 were a much HEAVIER jacket with a beefier braid of nylon material in the jacket for strength. ended up sending htem back and stickign with my crappy Musica 2.0 leads for now (just going to the subs till i can get two 3 foot replacement lines of somethin better). i like heavier wire -- not that the wire itslef is heavy but that the jacket it is in is heavy so as to hold up to being stepped on, pinched, have crap sit on it, etc etc etc...

I saw some monster indoor/home interconnects i liked a lot, just from eyeballing them though, haven't really done any homework, although i've yet to "hear" them (if u can actually say you 'hear' a wire) but i'm bettin the "home" stuff's built differently than the "car" stuff.

that high end mosnter home audio patch cable gear is damn good lookin tho i'll tell ya :)

lemme know about buyin that 5.0 somewhere tho... its more or less a "priority" to me. thanx

[Jstas]

Crutchfield

They have them in stock. I called them earlier last week.

I also am using the 6.0's and looks mean little. They don't need the extra heavy insulation because thay are wrapped in a braided metal. They perform better than the 5.0's I had in my Thunderbird. Less noise and absolutly no whining from any source, at all. I needed to replace the 5.0's because they were too long. I went from 16 foot cables to 12 foot cables.

[PoweredByDodge]

Originally posted by Jstas
don't need the extra heavy insulation because thay are wrapped in a braided metal. They

hmm -- well that woud explain it -- i figured it was just "silver nylon fabric" braid ... never thought it would have been metal.. damn.. in that case.. smaller is better ...lol

hey thanks for the heads up on CF tho :) <-- calling them tomorrow