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External Mic on Galaxy Devices

OP AdamOutler

29th December 2012, 09:49 PM   |  #1  
Hey guys, I worked on adding external microphone features to my device for a dog-gone long time yesterday... about 5 hours. Elite Recognized Developer Rebellos searched the code and we figured out that the device wouldn't recognize my mic because it's ohms are too low. The WolfsonMicro chip uses any value below 1000 ohms to signify button presses. Above 1000 ohms it signifies a microphone. My microphone is a 900 ohm microphone, so in all actuality, it's pretty high considering most are around 100-500 ohms. However, Rebellos and I managed to hack through it. I wanted to share this method.

My target device is a Galaxy Camera, but Samsung has used WolfsonMicro chips in their devices for a long time. This also works on the Galaxy Note 2 so Its logical to assume it will work on others.

Here's the finished solution. A Samsung 4-pole to 1/4" Mic adapter with a 200ohm resistor inline.



Introduction


The Galaxy Camera and Note2 require over 1000 ohms of resistance in order to recognize that a microphone is connected to it. So, there's two ways to do this.

1. Buy a microphone with over 1000 ohms of impedance.
2. Add some impedance.

Now, adding impedance will reduce the volume of the microphone, but that's not an entirely huge issue as adjusting volume is not a big deal. However, adding a resistor will slightly distort the waveform but even with this slight distortion it's not going to destroy the sound quality because it's a very slight ripple which in most cases will not affect the compressed recording quality.

Getting things together
Everything you need to add external, directional audio is available at Radio Shack for less than $35 USD. Buy a better microphone with higher ohms for louder sound. You get what you pay for.
1. 1/4" Mono In-Line Audio Jack (2-pack) - RS Part Number 274-0340 - $5
2. a set of Samsung Earbuds with 4-pole connections
3. optional - microphone Unidirectional Dynamic Microphone - RS Part Number 3303038 - $19.99 - note the old one is 900ohms. The new one is 600 ohms.
4. optional - Biasing Resistor - you will need to do the following equation to determine the ohmage of resistor you require. $5
1100 ohms - (ohms of your microphone stated in the manual) = ohms of resistor required to turn on the microphone.
1100 ohms - 900 ohms = 200 ohms of resistance required
5. Epoxy and Superglue $5

Building the adapter
Building the adapter is quite simple Samsung uses 7 wires in their headphones. Bare wire is not connected to anything. 3 are copper colored in clear shields there is a Blue or Green, Red and White as well. The 3 copper are the common leads The White is the microphone.
  1. Cut the connector off the headphone, leaving 3 inches of the cable.
  2. Cut all of the wires except for one Copper and the White wire.
  3. Strip and tin the Copper and White wires.
  4. Solder the copper wire to one side of the 1/4" Mono In-Line Audio Jack
  5. *Optionally* If required to exceed 1100ohms solder the resistor to the white wire
  6. Attatch the white wire (with resistor if used) to the center post of the 1/4" Mono In-Line Audio Jack.
    At this point you can verify your setup works.

  7. superglue the wire to hold it in place for the next step
  8. Mix up your epoxy and apply to the resistor, wire and jack connections in a way to support the following:
    1. to keep the wires from touching anything
    2. to prevent physical strain on the electrical connections
    You'll want to ensure that the epoxy is a light coat which totally surrounds the wire, resistor and large metal pads on the 1/4" audio jack. But don't let it go down inside the jack because it can prevent the microphone from connecting properly.
  9. slide the 1/4" jack cover down over the epoxy after it's done drying.

It should look something like this:



Here's a video showing how it works with my cheap microphone. It works super well to remove almost all noise from my recordings and just needs about a 6db gain and bass-boost adjustment in post-processing for accurate sound reproduction. This could be and will be corrected with a better mic in the future.

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Last edited by AdamOutler; 29th December 2012 at 09:58 PM.
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29th December 2012, 10:03 PM   |  #2  
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Probably could build a preamp circuit using an op-amp to handle the impedance shift without losing volume.
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30th December 2012, 12:21 PM   |  #3  
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FYI - Speech Filter
31st December 2012, 12:53 AM   |  #4  
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Does 1000 ohms apply to USB driven mics (somehow)? Or is it only a matter of drivers? To be specific I'm referring to the Snowball from Blue.
31st December 2012, 02:33 AM   |  #5  
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I'm considering adapting this mod to my specific needs. I'm looking to hardwire my lady's car for handsfree using google now. I have headphone audio in via a tape deck adapter. This mod would allow me to add an external mic mounted to the steering wheel or dashboard.

Is the mic functionality of this mod exclusive with audio output? Or could I keep the Red, Blue, and remaining copper wires and attach them to a separate 1/4" jack for audio out?

This would then give me a Y-Adapter, with one side for Mic In, and the other for Line Out.
31st December 2012, 02:33 AM   |  #6  
Quote:
Originally Posted by QNBT

Does 1000 ohms apply to USB driven mics (somehow)? Or is it only a matter of drivers? To be specific I'm referring to the Snowball from Blue.

If there is a way to configure that chip, its locked away in proprietary drivers. The ohms only affects the pins 1 and 2 in the OP. To my knowledge all samsung camera apps (GCam and Note2 tested) do not have the ability to record bluetooth or USB.
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31st December 2012, 02:39 AM   |  #7  
Quote:
Originally Posted by Adreaver

I'm considering adapting this mod to my specific needs. I'm looking to hardwire my lady's car for handsfree using google now. I have headphone audio in via a tape deck adapter. This mod would allow me to add an external mic mounted to the steering wheel or dashboard.

Is the mic functionality of this mod exclusive with audio output? Or could I keep the Red, Blue, and remaining copper wires and attach them to a separate 1/4" jack for audio out?

This would then give me a Y-Adapter, with one side for Mic In, and the other for Line Out.

It would work well.. to activate Google Now you simply open the connection between pins 1 and 2 momentarily... however, i posted a schematic for the entire audio controls via USB last year. It uses the Built-in FSA chip present in all Samsung Galaxy devices. You bridge USB PINS 4-5 WITH A 410kohm resistor and then using a set of 10 switches and resistors you can seek, skip, pause, and several other actions. The schematic for a car-mode audio dock is located in the USB chip manual.
Last edited by AdamOutler; 31st December 2012 at 04:16 PM.
31st December 2012, 02:47 AM   |  #8  
thats blody brilliant, from the looks of this, this mod would work for a wide spectrum of phones, I might atempt this with my evo 3d!
31st December 2012, 03:33 AM   |  #9  
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I cant help but think that this is one step closer to making the galaxy camera a full blown phone.
31st December 2012, 11:43 AM   |  #10  
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Adam,

I've found this on the net and thought it may be of interest to you.
These guys have worked on a similar project, but for the iPhone. On the wiki they stated that they couldn't get the android microphone to work, but I think you solved the problem.

I am unable to post links but the project is called BootlegMic, and the wiki is:

wiki dot openmusiclabs dot com slash wiki slash BootlegMic


Regards
Lutadore

Sent from my GT-P3100 using xda app-developers app
Edit: typos fixed
Last edited by lutadore; 31st December 2012 at 01:22 PM.

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