How to mate a cell phone with a computer?
November 12, 2005 8:08 PM   Subscribe

Cellphones + soundboards - anyone done this before?

Someone bought some adapters so they could connect a cellphone to their computer, but so far the cellphone output is really distorted, and must be amplified.

The quality when playing sound files from the computer into the cellphone is OK but really too quiet. Expert advice?
posted by fish tick to Technology (4 answers total)
It should be pretty straight forward - I assume you are using the handsfree jack on the cell phone?

You will have to adjust gains to make it work no matter what, of course. It is possible that you have volume settings too high somewhere, overdriving an amplifier and causing distortion that way.

You should be able to connect the speaker pin of the handsfree jack to the the computer's line-in pin and get a useful result (connecting ground too, of course). I wonder if the amplifier driving the cell phone speaker is Class-D. The cell might count on the low pass characteristic of the speaker to filter the signal. Try adding a low pass filter (at 10kHz maybe) between the speaker pin and the PC's line-in.

Remember that the microphone pin on the handsfree jack is powered and expects a microphone. You should have a coupling cap between the computer's line-out and the mic pin (otherwise the power supply for the mic will effect the line-out signal)... Actually, maybe a resistor from the mic pin to ground and then a cap between the mic pin and the line-out of the PC (without the resistor to ground the mic pin will float up to the cell phones +ve supply voltage, which may be an issue).

You might have software problems in your PC too. Make sure the line-in and line-out are working well with other equipment.

It is hard to guess at this stuff - much better to have it on a test bench to see what is actually happening.
posted by Chuckles at 1:06 AM on November 13, 2005

Try adding a low pass filter (at 10kHz maybe) between the speaker pin and the PC's line-in.

I'm not sure that I have thought this through enough... Just searching for explanations...
posted by Chuckles at 1:08 AM on November 13, 2005

If you happen to own a cell phone running on Symbian Series 60, you can purchase NaturalRecorder, an application that runs on your phone and will record your conversation to memory.

Details here.
posted by disillusioned at 3:01 AM on November 13, 2005

I've never tried to go in, but I use my cellphone's FM radio receiver function occasionally in music performance, attached direct to my mixer's tape ins. It works fine (sometimes too well, I'm not usually interested in clear radio sounds).

My phone is an LG PH-L4000V
posted by Joseph Gurl at 4:29 AM on November 13, 2005

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