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Discussion Starter #1
I found an Apple Airport Express 802.11n (version 2; supposed to have a better onboard dac) on craigslist for $40. So i bought it thinking it would be nice to be able to have my passengers airplay their music when they ride with me. So i setup the aex with an extension cord in my trunk to test it out; i set it to run as am access point with wpa. I jumped in and connected to it from an iphone, turned on started playing a track and was easily able to select the aex as the output target, and after a half second pause it started to play the track through the car's system. I was expecting to have a greater loss of quality! There were only two drawbacks to this, first if you're connecting to the aex from an iphone the phone expects the network to provide a data connection and doesn't use the mobile data connection, and second there is a sort delay when switching tracks, however i didn't notice any delay at all when changing volume from the phone. I also noticed that the device got pretty warm for just having it plugged in doing nothing for an hour and maybe 20-30 minutes of listening to music.
 

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So then i started to break it open and see how i could modify the power supply to accept 12vdc. I searched the web and found several people who had converted the original aex but i wasn't able to find anyone who did the same with the revision.

I wanted to have a device that looked close to stock as possible once finished. Apple seals the two haves of the plastic shells together using some sort of ultrasonic welder which melts the ends of the halves and seals them together. So i stuck the aex into a small vise and used a Japanese hand saw to cut into the plastic. I was able to only cut the two sides with the power connector and pry the case apart.

if i was more careful while sawing i think i could have made the cut much thinner.

Both sides cut, ready to be pried apart.


One half of shell houses the motherboard with all the connections and the other half has the powersupply.

I removed both boards (with the copper heatsink? removed) and left the aex plugged in on an esd mat for a few hours, when i came back i felt like it was cooler than when it was running inside the case. I was hoping that the heat i noticed was from the powersuply and not the motherboard, this however was not the case, the psu wasn't warm at all only 3 of the 4 'housings' were generating any heat.
 

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Discussion Starter #3 (Edited)
The next step was to make a 12vdc psu, i knew i wanted it to be able to remote turn on and i wanted to have a fuse.

The oem aex psu supplies 3.3vdc at 1.2A, so i decided to use an lm7805 to drop the cars output to a regulated 5v and then lm7111-3.3 to drop that to 3.3v; the max current the lm7111 can delever is 800ma, so i wasn't sure the aex would work, but it was all i had at home. So i tested everything on a breadboard as a proof of consept and the aex turned on and i was able to connect to it and play music (fyi: it wont show up as a selectable speaker unless something is plugged into its line out) and i had the world's worst (paritally) wireless headphones!

I then soldered decoupling capacitors on both regulators dead bug style and wrapped everything up with heat srink tubing.


For the remote turn on i had a small 5A 12vdc SPST relay to switch the power. I then moddified the oem power plug to house a blade fuse holder and a female 3 pin molex power connector:


I also moddified the 'back' casing (so much for staying stock; but function>form) to mount a passive 28MM chipset heat sink, the 'front' casing i cut openings for a pair of TO-220 1/2" heatsinks to help dissapate any heat from the regulators.





Once I had everything wired up and mounted to the 'front' casing i finally cut off the oem connector from the power supply and wired that to my fused & regulated power supply.


Again if i was more careful when cutting i could have made this much cleaner.

The entire album.
 

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Discussion Starter #4
Before i figgured out a way to reseal the casing together i wanted to bench test it with 12vdc since everything was mounted in the case this time i left it playing music for about 30 mintues to see how well the heatsinks work and to verify the 800ma power output would be suffecent when the aex is at opperating temp, after 30 mins the aex was still working perfectly and the motherboard was barely warm. The regulator heatsinks however were another story the lm7805's heatsink was so hot i ended up slightly burning the tip of my finger, the lm7111 was just a little warm.

My idea atm is to replace the lm7805 with a 5volt buck converter which regulates the voltage by switching on and off really quickly. This means there is no heat produced, but its output will be rippled. Im assuming it will resemble a sine wave after the filtering caps, im not sure how clean the output of the lm7111 will be and if any noise created by the psu would affect the aex. http://www.diymobileaudio.com/forum/car-pc-forum/119401-efficient-3-3v-linear-power-supply-questions.html Unfortunately i haven't had the time to look into which buck converter to buy and test the efficient psu.
 

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Discussion Starter #6 (Edited)
Good work.

If you don't absolutely need Airplay then a Pure I-20 dock is better in ever way.

It's also only $99

http://www.diymobileaudio.com/forum/member-reviews-product-comparisons/109034-pure-i-20-digital-ipod-dock-analog-output-rmaa-measurements.html
Ya ive seen the product, and if this was going to be my primary input i would have defiantly gone that way. If i ever switch the ms-8 for a bit-one the aex will also do (bit perfect)optical output. But the aex will only account for maybe 10% of system play time, mainly on (longer) road trips once people get sick of my library.

Most of the time im in the car alone and ill be playing music from my ipod touch which is controlled by the factory head unit via a dice ipod interface. the airplay will only be for when someone else wants to play a song from their phone/itouch/laptop. I like the idea that on road trips i can unplug my ipod and be able to pass it around without worrying about any wires.
 

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So i went ahead and changed to a switched/linear setup; and i haven't noticed any negative issues. i wish i had access to an o-scope to see what the output looks like..

anyhow for those who want to know what i used:

i selected the LM2575T-5.0 for the buck converter it can accept 7vdc upto 40vdc, and outputs 5v at 1a

following the recommended usage there is a 100uf cap before the buck converter and diode, 330uh inductor, and a 300uf cap on the output.

that then feeds a LT1086CT-3.3 linear regulator; i decided to use this regulator as its rated output is 1.5a @ 3.3v.

my car was down due to a mechanical problem for the last week, but im just field testing the aex for a few more days before i figure out how to seal it back together. I didn't take that many photos this time, with the exception of the inductor it doesn't look like much has changed.

the first attempt i had the 330uf cap sitting on top of the inductor, but this was too tall and ended up hitting the motherboard.

so i ended up putting the cap next to the inductor (both under the heatshrink) and now there are no clearance issues.
 

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I got one in the mail about to do the same thing. Funny I was getting ready to order it when I stumbled across this thread.

I have some electronics background so I was immediately going for a switching power supply. Linear regulators are old technology and the ripple has been greatly reduced. Sure, linear regulators still have their place in high precision applications, but there is no beating the efficiency of a switching supply.

I'll be sure to post pics once I am done :)
 

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Discussion Starter #9
Awesome! be sure to add a link to your thread, or if you want add photos here itself. ive timed the unit from the time it gets power until the wifi goes active (~85 seconds) and then until my ipod detects and connects to the aex (another ~8 seconds). so its not the most practical input source if your planning on using it as the primary input.
 

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Ok so I registered to ask this. I may have figured out a way to access the 3G data while connected to the airports network thus enabling AirPlay and 3G data at the same time. Can you confirm for me if this works please! This is what you do,

on your iPhone Connect to your wifi (the Airport) and write down the IP address your router assigned you. Then on the iphones wifi setting screedn select static tab instead of DHCP and fill in the IP address your DHCP server assigned to your iPad. Next, fill in the subnet mask but leave the rest of the fields empty.
You now have access to your wifi as well as 3G.
 

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Hi, I joined just to ask this question. So I seemed to have figured out a way to use the WiFi and the 3G data at the same time, so basically you could connect to the Airport and still use the 3G data for a music source basically. Here is what i found, please try this out and let us know if it works, thank you.

Found this on another site:

Connect (your iPhone) to your (Airport) wifi and write down the IP address your router assigned you. Then, select (on the iPhone) the static tab instead of DHCP and fill in the IP address your DHCP server assigned to your iPad. Next, fill in the subnet mask but leave the rest of the fields empty.
You now have access to your wifi as well as 3G.


Please test and respond if this works! Thanks man
 

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I picked up an older gen Airport Express that requires both 3.3V and 5V. I used preset switching TI power modules, they should be about 91% efficient at this load, and have a wide range of input voltages.

I'm going to pack the rest of the case with some random caps I have laying around to try and get the thing to stay powered on for a few seconds, so it will stay on while I start the car.





It's sitting in the center console on my TL, that has a switched 12V plug and 3.5mm aux in right next to it. Super simple.
 

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I agree it has some flaws, probably due to it not being designed to work in a car application.

However, it was cheap, takes very little power, is small and easily hidden, completely wireless, and very simple to use once set up. I get in my car, my phone auto-connects to the WiFi, and it works without plugging anything in. Most apps even prefer the AirPlay once you connect to it once, so you don't even need to select that again. As long as its in range, it works. The phone can be sitting in the cup holder, my pocket, wherever.

The only real downside is it takes something like 90 seconds to boot up. Big deal, I probably won't use it much anyways. If I wanted real integration and charging support, I would swing for the iSimple or something like that, where I could get track info on the display as well as change tracks from the wheel.
 

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I agree it has some flaws, probably due to it not being designed to work in a car application.

However, it was cheap, takes very little power, is small and easily hidden, completely wireless, and very simple to use once set up. I get in my car, my phone auto-connects to the WiFi, and it works without plugging anything in. Most apps even prefer the AirPlay once you connect to it once, so you don't even need to select that again. As long as its in range, it works. The phone can be sitting in the cup holder, my pocket, wherever.

The only real downside is it takes something like 90 seconds to boot up. Big deal, I probably won't use it much anyways. If I wanted real integration and charging support, I would swing for the iSimple or something like that, where I could get track info on the display as well as change tracks from the wheel.
It was a great option when Airplay came out and the only digital docks where ridiculously over priced and/or very hard to find.

The other 3 huge issue for me are that:

-You loose all type of cellular data ability since it thinks it is connected to the internet and funnels anything it can through it for efficient.

-It looses sync with the APE every time you pause or change track when using the toslink output. That leads to full scale pops from the DAC.

-You have to switch over to Airplay each and every time you start the APE.

-Doesn't charge the device and kills the battery at the same time with the WiFi radio.
 

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It was a great option when Airplay came out and the only digital docks where ridiculously over priced and/or very hard to find.

The other 3 huge issue for me are that:

-You loose all type of cellular data ability since it thinks it is connected to the internet and funnels anything it can through it for efficient.

-It looses sync with the APE every time you pause or change track when using the toslink output. That leads to full scale pops from the DAC.

-You have to switch over to Airplay each and every time you start the APE.

-Doesn't charge the device and kills the battery at the same time with the WiFi radio.
I have the Airport Express set up so that my phone still has cellular data.

I could see how that would be an issue with some DAC's if you were using the optical out, I'm just running analog into the cars stock input. Getting the absolute highest fidelity out of it really isn't that big of a deal, since everything in my car is stock. It sounds better than most cars, but its not stunning.

This was just something I wanted to try. I don't know how much use it's going to get, but I really don't have any big issues with it yet. I still prefer it over having to plug the phone in. Then I need to worry about the phone flying around, or mounting something to my car.
 

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I have the Airport Express set up so that my phone still has cellular data.
I could see how that would be an issue with some DAC's if you were using the optical out, I'm just running analog into the cars stock input. Getting the absolute highest fidelity out of it really isn't that big of a deal, since everything in my car is stock. It sounds better than most cars, but its not stunning.

This was just something I wanted to try. I don't know how much use it's going to get, but I really don't have any big issues with it yet. I still prefer it over having to plug the phone in. Then I need to worry about the phone flying around, or mounting something to my car.
Cool, did not know that was possible. Thanks for the heads up.
 

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Cool, did not know that was possible. Thanks for the heads up.
You can do it this way...

Found this on another site:

Connect (your iPhone) to your (Airport) wifi and write down the IP address your router assigned you. Then, select (on the iPhone) the static tab instead of DHCP and fill in the IP address your DHCP server assigned to your iPad. Next, fill in the subnet mask but leave the rest of the fields empty.
You now have access to your wifi as well as 3G.

Or you can also configure the router itself to do effectively the same thing on its own, making it so any device that connects won't look to the router for internet. This way is a bit more involved.

I think this is a great solution to add relatively long range wireless audio into most any car. These things can be picked up for $30 or so, and are quite easy to mod for anyone with a bit of electronics experience. It works beyond where you can hear the audio blasting from the car with the windows down, which is probably good enough.
 
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