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October 5, 2006
Building an Aux Input Cable for Bose SoundDock
Update: I've had a number of requests from folks interested in purchasing this cable. If you don't want to go through the trouble of making one for youself, you can now buy one from CableJive.
It's been about 3 months since I hacked my Bose SoundDock to include an auxiliary input. I've gottent a fair amount of response from folks about it, SoundDock owners everywhere are seriously interested in being able to listen to more than just the iPod on the speakers. However, most folks aren't up for pulling the unit apart and taking a soldering iron to it. A lot of folks have wished for a cable that simply plugs into the iPod connector.
Here's how to do it. With the right tools and supplies it doesn't take more than a few hours.
First order of business is getting a female iPod dock connector from Ridax to plug into the SoundDock. I don't believe there's a home-made solution to this, you've just got to wait for Ridax to get the order processed and the mail to snail it's way to your house. While shopping at Ridax you might notice that they now have a SoundDock friendly adapter that takes a 1/8" jack. Perhaps you'll decide that's a better option, in which case you can skip the rest of this exercise.
I ordered two of the white female adapters a few months back. It took them a few weeks to arrive, and then they sat on my desk for a long time waiting for me to get motivated to tinker. The adapter is easily pulled apart and as you can see has a small metal piece with the stretch of exposed pins that you can use to make connections through the female adaptor to the iPod-compatible device.
Once I had the adapters in hand I wrestled with how to figure out how the SoundDock is activated. My first aux input hack required leaving the iPod on the SoundDock for power activation. With this female adaptor hack I needed to figure out how to turn on the SoundDock from the adapter. I figured worse case scenario is that the SoundDock detects a small battery charge and uses that to trigger the power. The easier place to start was some testing to determine if bridging any of the pins triggered the SoundDock to turn on. After a little trial and error, I got the SoundDock to activate by connecting pin 18 and 19 (counting from left to right). The iPod Connector specs indicate that these are voltage pins. For whatever reason, connecting them triggers the on switch for the SoundDock.
Important notice, please ready the update at the end of this post. There's is more to the story for powering on the SoundDock.
To make that connection permanent I pushed the 18 and 19 pins together until they were crossed and making a solid connection. For good measure I stuck a small spec of solder on the two pins to make the connection more permanent. Not easy to solder on such a small scale, but sitcking just a small shaving of solder onto the crossed pins and pressing the tip of the solder iron down did the trick. Of course I tested to ensure that popping it on the SoundDock did indeed activate the unit. With that major issue resolved the rest was fairly straightforward.
The iPod connector specs indicate that pins 1 & 2 are grounds (connected together on logic board of iPod), pin 3 is right line out, and pin 4 is left line out. I had a spare 1/8" jack with a 2 foot cable in my cable box that looked just right for the job. (I thought about using an RCA-type plug but I think the 1/8" jack will be more universal for my use). After putting a small knot in the end of the cable to help keep it secure in the female adaptor housing I stripped back the ground, left and right wires just enough to give space for soldering. I should add at this point that soldering on these tiny prongs is a challenge, especially if you don't have any special soldering equipment (I have a $10 kit from RadioShack). I was able to get fairly nice, solid solder connections but sensed some risk that there could have easily been a drip of solder that would have covered and connected 5 or more of the tiny pins. You'll notice in the picture that I snipped off a few of the unused pins to the right of the audio connection pins just to free up some space.
With the cable soldered in place I put a good blob of clear epoxy over the soldered wires and pins to reduce movement and ensure the wires would stay in position and not accidentally short out.
After giving the glue some time to dry I snapped the unit together and have been listening happily to my laptop via the SoundDock ever since. It's worthy of note that the sound quality from the SoundDock is much improved over the original hack. I suspect it's because when the iPod is attached the audio out from the iPod causes problems with the aux input, even though the iPod isn't actually sending a signal. The extra hiss that I noticed in my first hack is completely gone when using this cable/adapter.
Important update: Some digging around with the multitester indicates that the SoundDock provides 12V, 500 mA from pin 19. Looking at the dock connector specs indicates that on pin 18, the iPod provides a 3.3V output. Using the multitester on my 4G iPod indicates that it outputs 3.3 V, 40mA. I checked using two 1.5 V batteries and indeed, providing ~3V to the SoundDock on pin 18 triggers the on switch. As documented above, I'm sending 12V, 500 mA into pin 18. It works, but may prove harmful over time. To convert the voltage and amperage down to a safe level a resistor should be used between pin 19 and 18. My calculations indicate that this should be a 250 Ohm resistor (drop 12 V by 8.7 V to be 3.3 V with 40 mA). Am headed over to the electronics shop at lunch to pick a range of resistors up and will update with information when I have a chance to try it.
Final Update: After a few trips to Radio Shack, some diagnistoc work, and conferring with a retired college professor/electrician (my father) I have a final update on connecting the current from pin 19 to pin 18. Pin 19 outputs 12V (firewire, used to charge the iPod). Pin 18 accepts 3.3V (for the iPod to power accessories) and uses that to trigger the on switch of the SoundDock. Initially I thought putting a 220 Ohm resistor between the 12V and 3.3V would reduce the electricity by 8.7 volts and be just what is necessary.
Unfortunately it isn't that simple. A resistor only reduces voltage if there is a significant draw in amps (or milliamps). Circuit 18 draws almost nothing, so putting a resistor between pin 19 and 18 made no significant change in voltage. The amount of draw is undetectable by my multitester. It can go down to hundredths of a milliamp and still wasn't registering anything when attempting to test the draw of electricity from pin 18.
The good news about that is that the SoundDock doesn't seem to be actually using the electricity coming in on pin 18 other than detect that there's some current there. So my original attempt to make a direct connection between pin 19 and 18 to trigger the on switch by sending 12V into the 3.3V doesn't seem to cause short-term damage. It's uncertain whether it causes long-term damage, as pointed out in the comments. Until someone verifies the electronics inside the SoundDock, or an engineer from Bose comments here, it's risky to send the 12V from pin 19 directly into the 3.3V on pin 18. It may prove to be damaging in the long run.
For those of us who'd like to play it on the safe side, there's still a way to reduce the voltage by hooking up resistors in serial and tapping out at the right point to get 3.3V.
Without going into a lot of electrical theory the idea is that you want to connect the 12V to the ground through two resistors, selected in a ~4/1 ratio. If you tap out between the two resistors you will get approximately 1/4 the voltage coming off the 12V. At first I chose a 1K and a 220 Ohm, put the 1K on the 12V side and the 220 on the ground site. Tapping off between them provided just about 3.3V. Since the SoundDock requires almost no current I decided to try a 10K Ohm on the 12V side and a 2.2K on the 3.3V side (both 1/4 watt resistors). Even with close to 0 amps coming off the tap between the two resistors the SoundDock powers on. I believe this is the best method (using the 10/2.2K resistors) for channeling power from the 12V to the 3.3V as it provides only a bare minimum current. I've made a few of these now and will take some photos to post on the next one I make.
Making this cable is just a bit more challenging when you have to put the resistors into the small connector housing.
Posted by mike at October 5, 2006 10:13 PM
Comments
Just want to clarify that this is NOT the way I am doing the Bose Sounddock line in adapter.
The description here sounds potentially dangerous for the Sounddock and nothing I can recommend.
Posted by: Mikael Wahlgren at October 9, 2006 4:36 AM
Thanks for the warning Mikael, I revisited the section on powering on the SoundDock and have updated the tutorial with more information on doing this safely.
Posted by: Mike Kruckenberg at October 9, 2006 11:33 AM
Hi,
I would recommend against saying that it is "likely to not cause any damage to the SoundDock" to put 12 V (actually up to 17V) on a 3.3V input. How do you know that it is likely to not do any harm in long term? You have only known this solution for about 1 week and can't possibly know any long term effects, unless you have checked the hardware and made calculations yourself.
There are several ways that the Sounddock could have designed this "iPod detection" scheme hardware wise. They could have routed the 3.3V input directly to one of the inputs of the microcontroller they are using (through a resistor). In this case the controller is probably having internal protection diodes on the input pins that draws overvoltage on the pin to VDD. This diode will protect the controller from damage under a limited time for "occasional mistakes", but the diode could be damaged under a constant overvoltage that is so high. Once the protection diode is damaged, the controller will be damaged as well, as the 17V voltage (14V overvoltage) will come directly into the controller. Once the controller is damaged, it is goodbye to your Sounddock.
Another possible hardware design is that they have a transistor with the base connected to the 3.3V input through a resistor. If you inptu 17V on the 3.3V input in this case, you will get a base/emitter voltage of 17V and this is more than many transistors will tolerate in long term operation (a very common BC547 has a base/emitter voltage max of 6V, not meaning it MUST break immediately because of over voltage, but in long term, the life time is definitely in danger). I don't know the hardware design of the Bose Sounddock, as I have no need to open it up and void the warranty.
You should NOT encourage people to believe it could be safe connecting pin 19 and 18 directly. Well, it COULD be safe doing it... but it COULD AS WELL result in a lot of damaged Sounddocks after a short time.
Posted by: Ridax at October 16, 2006 3:59 AM
Hi,
Your electronics is still a little off. You want to select the two resistors R1 and R2, such that R2/R1~3/1. This will give you 3V at the tap.
With a 10K and 2.2K, you are supplying 12V*R1/(R2+R1)=2.2V. I doubt there's any problem with underpowering the Soundock, so it's nothing to worry about.
Anyway, thanks for the great tutorial. I'm just about to wire one up myself.
Posted by: enerd at October 26, 2006 10:24 PM
I chose the 10K/2.2K because while the output is supposed to be 12V, without any load on pin 19 the voltage is closer to 18V. If you put a true 1/3 ratio resistor pair on there you'll actually be somewhere up near 5 or 6 volts. On my multitester the 10K/2.2K puts the tap just a hare above 3V.
I need to rewrite the tutorial with new photos that feature how I'm putting the resistors in there, just haven't had time.
Posted by: Mike at October 26, 2006 10:32 PM
Do you think there is a way to just make an extension for your iPod, so that you don't need to remove an iPod skin to put it into a dock or speaker set?
Posted by: Jeremy Curry at November 5, 2006 4:57 PM
I have an Evo3 iSkin and found that if I remove the white cradle cover adapter that my iPod fits on quite nicely. It rests against the speakers with the clip that's on the back of the iSkin which I'm ok with.
As far as the cable, I haven't tried anything like that.
Seems like if you connect the pins directly through between a female and a male adapter that you'd be able to accomplish this. For sure you need pin 1,2,3,4,18, and 19 to get the audio from the iPod (1,2,3,4) and provide power from the iPod to trigger the SoundDock to power on (18) and provide a source of power to the iPod (19). That doesn't give you any control over moving between songs or pausing the music. Haven't had a need to figure out what pins are needed to do that.
Good luck, would be curious to see if it works.
Posted by: Mike at November 5, 2006 8:14 PM
Hey- Ridax has a logic board inside thier female ipod connector/cable. Why cant we find out what kind of resistive circuit they are using?
Do they guarantee that thier fix is safe over time for our sounddocks?
I dont wanna pay 59. dollars for something I can easily solder together.
Tony
Posted by: Anthony at November 11, 2006 11:58 AM
Can an IPOD Specific extender cable (~3 ft) be built with a Male IPOD connector to Female IPOD connector? This way I can still use the Bose remote, add songs to playlist, charge... or whatever, while sitting comfortable on the couch with the ipod in my hand.
How many individual lines would have to go from connector to connector.
Thanks
Tom
Posted by: Tom at November 20, 2006 11:08 AM
Tom - In theory this could be done. If you purchase a male and female from Ridax or Sparkfun you should be able to connect all 30 pins directly from the female to the male. There's probably a subset of those connections actually used, but I haven't done enough research to know which ones.
Posted by: Mike at November 22, 2006 12:46 PM
I've had a few questions on the electronics and if they are safe. Here's my calculation, I have an analog Simpson160 multitester which I'm using for voltage measurements.
The voltage on pin 19 without any load is just under 18 volts. The voltage required for powering on the SoundDock comes from the iPod on pin 18. The spec says it should be 3.3 volts.
I use a 10K and 2.2K resistor, 10K from the 18V side and 2.2K on the ground. This means that at the tap, the 18V is being reduced by 81.9%, or by 14.74 volts. 18V - 14.74V = 3.26V being sent to the SoundDock on pin 18. This math could be improved with a digital multitester, which I do not own.
I don't want to be irresponsible, but that is close enough for me to believe this hack isn't going to hurt my SoundDock over the long run.
But just to be sure I continue to use the cable. I regularly swap between cables to turn the power on/off and when I'm not at my desk I leave a cable attached to keep tests of the long-term effects of the electronics on the SoundDock. By my calculations, I've logged just under 1000 hours of powering the SoundDock with this since the first day I put this hack out there (before I had the electronics all ironed out).
Mike
Posted by: Mike at November 22, 2006 1:24 PM
OK, so if I dare to take the challenge of trying to make an extender with all 30 wires; any recommendation on wire gauge(can they all be the same of one gauge), or where to get the wire to do this.
Tom
Posted by: Tom at November 25, 2006 10:00 AM
OK,
I realize that I am not alone....I too have an iPod and Bose Sound dock...and yes I want to do other things with my sound dock. But here is my issue....I have forgone my stereo and other equipment and went cold iPod...one reason was that I relocated to an area where it's all 220...no biggie...but now I want to listen to the radio through my iPod....and pump it out through my Bose dock while charging my iPod...I want to purchase the Radio tuner for the iPod but that means using the 30 pin connector on the bottom of my 5th gen iPod...I hate the fact that they removed the power connection on top....that would have solved all my problems but....such is not the case....now I am leaning towards Ridax's bose line in connector...and posssibly using his extender board to power the iPod...but I do not want open circuits around my kids...so anybody have any good suggestions? Love to hear it...
thanks
Dave
Posted by: Dave at December 23, 2006 1:57 PM
DO YOU MAKE THE CABLE SO THAT I CAN PLUG MY IPOD IN THE OTHER END 4 MT LONG.
Posted by: mr marshall at January 12, 2007 4:21 PM
can i used this adadtor to convert my connection in my car stereo since i only got an ipod connection, so that i can connect my other mp3 player in my car stereo.
Posted by: rey at January 25, 2007 7:15 PM
Just got my SoundDock & love it - Of course, like everybody else, I'd like to use it for my than just my ipod, so, this input mod is perfect - my only question is how safe is it/will it damage the soundDock & WHY hasnt Bose themselves put something as simple as this out?
Posted by: Jake at January 27, 2007 2:46 PM
Any chance of making up a 30 male to 30 female connector?
Posted by: Shawn at January 27, 2007 7:51 PM
Has anyone ever considered try to figure out a hack to wire a stand alone sub-woofer to the Sounddock?
I love mine but it sorely lacks in the base department.
Posted by: Mike at January 31, 2007 1:55 PM
Why don't you check to see if the dock is putting out 5V for USB on pin 23? Wouldn't it be simpler to put the USB 5V to pin 18 if the power is available?
Posted by: Max at February 8, 2007 2:08 PM
New Ideas for safer Aux . . . modify your SoundDock Extension so that instead of having the Audio In coming from iPod, it comes from another source. So, you need your iPod plugged in to regulate the voltages, but then you have another Audio Source.
Or . . . what is the deal with the "Audio In" pins, next to Audio Out? I assume its for the microphone options. Will the iPod just pass that audio through if you run that to your Aux?
Posted by: Kevin at February 14, 2007 11:35 AM
So the circuit diagram looks something like this, I guess. If it's all wonky, copy and paste it into notepad, and that should fix it.
1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19
| | | | | | | | | | | | | | | | | |
│ │ │ │ │ │
│ │ │ │ │ │
├──┘ │ │ ┌──────┘ │
│ │ │ │ │
│ │ │ │ │
├─────}──}────────────────────────[2K2]──┴──[10K]──┘
│ │ │
│ │ │
│ │ │
G R L
Posted by: Anon at February 25, 2007 5:49 PM
is there anywhere I can just buy such a cable other than DIY?
Posted by: Joey at March 5, 2007 5:01 AM
Joey,
Yes, you can buy one. As mentioned at the top of the article in the update you can get an aux input cable for the Bose SoundDock from CableJive:
http://www.cablejive.com/sounddockcable.html
Posted by: CableJive at March 5, 2007 9:16 AM
Anywhere you can buy one cheaper????
Posted by: Alex at March 24, 2007 12:25 PM
What's the deal with the resistors? I can solder and all that, but can someone draw up a schematic for it or something?
Posted by: Brandon at April 7, 2007 2:16 AM
Hello there,
I would like to be able to connect my iPod to the USB on the front of my car stereo WITHOUT the stereo taking control of the iPod, meaning that I use the iPod clic wheel to choose the music I want to hear, instead of the awkward one line cd player's display. I imagined I could alter the originall USB to iPod cable, but I don't know how to go about it.
Would somone have an idea?
Thanks
Alexis
Posted by: Alexis at June 21, 2007 6:02 PM
I would like to add a 3.5 jack plug on my bose unit to add aux, and leave my ipod conected. would this mess up the system, or does anybody know of a bose system which already got an aux on?
#
Posted by: REBELION at August 2, 2007 7:57 AM
please send pin diagram of ipod data cable
Posted by: yasar at August 13, 2007 1:06 PM
Why would you go through so much trouble with a speaker system that cannot even produce 1/2 of 20hz - 20,000hz range? They have much better systems out for you to mod.
Posted by: Guido at August 13, 2007 8:41 PM
Hello. I've got a problem with my SoundDock. I've bought this on eB.. and the power supply was not present, So I don't know where the 4 wires needs to be connected .. because the wires are snatched from the dock ! ;-)
Is anyone can help me ? Maybe with a schematic of the card ? If it's not clear enough, please tell me .. my English is approximative ;-)
Posted by: Oliver at May 27, 2008 10:20 AM
You are the MAN!!!!
This thing works great. I bought the female connector and receptacle from Ridax and started working on it. The truth is that this thing is tiny, much smaller that I thought. It took me about an hour to solder those three little pins with the wires, but it was a success. the pins that I didn't use, I just pulled them off, and left the 18 and 19 and touching each other and done. Then, instead of silicon I used wax from a candle to cover and protect the circuit, I know it´s pretty weak, but that's what I have right now.
Any way, I don't thing the resistor thing is really necessary, mine works great without it. Thanks.....
PS: you should patten it and sell it, many people are looking for this..
pec
Posted by: Pec at September 1, 2008 3:00 PM
Hello Mike,
Your page is great. I would like to use your ideas, but I would like to know if you can provide a schematic or circuit diagram of the pcb on the front of the sounddock where the ipod is fixed, as my pcb broke and was thrown away by mistake. Only the flat ribbon cable protrudes in that area now.
Alternatively are there any sites where one can see a sounddock schematic.
Many thanks
spd
Posted by: spd at October 7, 2008 11:22 AM
Hello there,
This page is very interresting!
Is it possible that someone sending the FINAL SCHEME with pins and 10K/2.2K resistors conneting?
This is a great idea....the pleasure of Bose Sound for an another mp3 player !
Thanx
Posted by: Steph at October 8, 2008 9:21 AM
Hi there;
I have purchased a sound dock that has a broken power connecter at the pcb. I have the cord and even the plastic plug that goes over the pins. I only have 2 pins on the board however. It looks like the front two have been broken off. Can anyone provide pin layout into as to which pins on the board are + and -?
Thanks,
Jerry
Posted by: Jerry at October 23, 2008 2:22 AM