iPod Touch Mods

The time has come to start to write a step-by-step HowTo on building your own Mic for the Touch. Not because I have too much time, but because it is hard to answer 20+ different mails per day discussing the same topic.

Pls follow the tutorial step-by-step. Remember: you are doing everything for your own risk! You know what you are doing, you understand the circuit. If you mess up tour Touch (or other iPod) you will not blame anybody but you.

So, let's start. This tutorial discusses the Schematic from Nov. 25 (Non-SMD!!) based on the TL272 IC.

1. Study the circuitry. Try to find all the corresponding parts you ordered from Conrad, or other Companies.


UPDATE 23.12.2007
The polarity on the CAP (capacitor) and MIC (microphone capsel) matters.
the (+) pole of the Mic is the top one on the schematic, connected to the 6k8 resistor, while the (-) of the Mic is the bottom one connecged to Ground (GND). It is VERY EASY TO DAMAGE YOUR MIC IF OVERHEATING IT; SO PLS BE CAREFUL!!!!!!!

Setting the capacitor properly:
If you use the Conrad Mic with 6k8, then there should be Ucc/2 = 1.66V on the (+) of the Mic,
AND you do not need to worry about the poling of the capacitor, but worrying about the polarization of the Mic capsule - YES!!
In case you use a Mic from another source (Not exactly the Conrad one), you can measure the voltage on the Mic. If that is higher than 1.66V, then you put the (+) of the CAP to the (+) of the Mic. Vice versa vice versa. Hope it is easy to understand ;)

I am sure people using non-conrad mics will post the voltage on their Mics.
Thnx!!! M.

Dock Connector:

http://home.swipnet.se/ridax/connector.htm
THEN click "Male iPod cable plugs" and you will see it on the right side.
Ridax knows which plug we are using, just ask him for the same ;)
Price: $2.10

Now you have multiple options toget the REST OF THE parts:

a) Conrad parts listed again Below - approved:

1 ST x 302007 MIKROFONKAPSEL .. Eu 5.6- each
1 ST x 147567 TLC 272 CP .. Eu 1.6- each
1 ST x 402427 SMD WIDERSTAND 100R 1206. . Eu 0.09- each
1 ST x 402648 SMD WIDERSTAND 6K8 1206 .. Eu 0.09- each
3 ST x 402680 SMD WIDERSTAND 15k 1206 .. Eu 0.27- per 3pcs
+ any SMD capacitor between 100nF and 5microF .. Eu (0.5 - 2.5) each

b) Newark Parts below (to be verified!!):

OpAmp: Newark Part Number: 08F9088
Manufacturer Part No: TLC272CP. Price: $0.44 each

Cap: Newark Part Number: 21M6465
Manufacturer Part No: B45196E2225K109, Price: $0.44 each

mic: Newark Part Number: 26M0647
Manufacturer Part No: MB4015ASC-1, Price: $2.92

15kOhm Res: Newark Part Number: 98K7579
Manufacturer Part No: 232271161153, Price: $0.60 for 50 (.012each)

100 Ohm and 6k8 part numbers still missing!!

c) Digikey Parts below (to be verified!!):

OpAmp: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=296-1824-5-ND
digikey Part Number: 296-1824-5-ND
Manufacturer Part No: TLC272CP, Price: $0.88 each

Cap: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=478-3054-1-ND
digikey Part Number: 478-3054-1-ND, Manufacturer Part No: TAJR225M010R, Price: $1.08 each

mic: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=423-1047-ND
digikey Part Number: 423-1047-ND, Manufacturer Part No: MB4015ASC-1, Price: $3.64

15kOhm Res: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=311-15KETR-ND
digikey Part Number: 311-15KETR-ND, Manufacturer Part No: 232271161153, Price: call for price

100 ohm
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=311-100ERCT-ND

4.7k ohm (instead of the 6k8 - as we are not using the same Mic from Conrad)
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=311-4.7KERCT-ND


2. Take the Dock Connector (most probably provided by Ridax) and study it a little. Pin nr. 1 is on the right side, pin nr 30 is the left most one.



3. As you know, we only need pins 13, 26, and 29 (eventually 30). So, now take your tool, and pull out the pins one-by-one and keep counting: "one, two, three....." ops! you removed nr. 13? Hope not! But if yes, just send another mail to Ridax. he will be happy with you :) Plugging back the pins will most probably not help too much, except.., maybe in case of pin 13, as the IC can hold it into his original place if your counting was already at 14-15 :)



4. Now that you have the Dock Conn Ready, we are going to prepare the IC for hosting the 5 resistors and the one Capacitor.

So, you need to make legs 1-4 totally horizontal, then turn leg 8 behind and then below (!) the IC totally. Now try to remove legs 5, 6, and 7. We will not need them. (The professionals would argue and connect them to Ucc and Gnd, eventually, but we will not do that). No need for it, believe me! (see photos below)

5. You now install one resistor between the legs 1-2 and another one between the legs 3-4. The first one is the feedback resistor of the amp (something between 10k and 20k), while the other one is the bottom half of the voltage divider.



6. Ok, now position the IC in a way the Dock will host it. Try to fit into the Dock. You will need to shorten leg nr 26 a little, as it almost reaches also the leg nr.2 of the IC. Coming from the right side, the IC should reach the leg 26 exactly and there will be a 0.5 mm space between leg 8 and pin 13 on the bottom side!! But you see, how nicely leg 13 holds the IC? Exactly fitting till the top of the dock conn.



7. Ok, now you connect the leg 26 and IC pin nr1. Then you turn the IC and...


8. .. and you put the 6k8 resistor in a way that it connects both, dock pin nr 13 and IC pin 8 (Ucc). No more 0.5 mm space. Now you are asking: "why we left that space there?" I will show it at the very end. Ok, now if you check the IC a little, you will feel, there is a little play relative to the dock conn body. This is exactly a design trick. I mean a mechanical trick, as the IC will touch 3 things: pin 13, the dock ceiling and also the back wall of the dock.



9. Now, you add the second resistor of the voltage divisor (must have the same value as the other half was), just next to the 6k8 resistor. But not touching the 6k8!!!



10. Turn the construction back, add the 100 ohm resistor (one side of it is in the air, so you will need to fix it somehow.. I used those paper covers of the SMD resistors to hold it while fixed).



11. If you are done, you add the Cap just as a continuity of the 100Ohm, but turned 90 to south. (remember, we have limited space inside the Dock Conn House!). The capacitor can be anything between 100nF and 5microF, but must be SMD!




Ok, let us know when you reached the last point, and I will upload the next part. Until then ...
Believers who want to support the Project may click on the "Donate" button at touchmods.net. Thnx.

Acknowledgements:
PHiL .. redrawing the schematic
RxE .. the Newark and Digikey part-lists
darkone .. Digikey Part List

Thanks!
Marian

Many of our friends at the ipod Touch-fans forum did ask if I will provide the details of the circuit so that they can build it by themself. Well, here it is:


A little description:
- 13, 26 and 29 are the pin indices of the Dock Connector.
- The Resistor above the mic could be around 5kOhm, depending on your mic (see the note below)
- The capacitors C1 and C2 should be above 1microPharad, any vale is ok.

The picture quality is not the best, as it was made in a fast way on my N770 using the amazing Xournal noteTaker.
Anyway, what is important, in case you plan to build everything inside the Dock Connector, you will need to make a PCB that is all-in-all less than 3.5x 8x 16mm, as the internal height of the Dock Connector is 3.5mm. Not to mention that the position of the PCB will be also restricted (centralized) by the pins inside the plug. A smart solution would be to leave the PCB out and to put the resistors directly onto the legs of the IC. I will post a photo soon showing what I mean.

Dock Connector Pinout: ipodlinuxTeam

Believers who want to support the Project may click on the "Donate" button at touchmods.net. Thnx.
IMPORTANT!!
When using the tiny mic from the other posts, the Resistor above the mic should be 6,8kOhm. Simply, the best choise is when the voltage at the top of the mic is close to 1.65V, given, that Ucc=3.3V. Then there is no voltage on C1, ie. no transient clicks when you plug it in.