Olimex Support Forum

OLinuXino Android / Linux boards and System On Modules => A10s => Topic started by: kbro on June 18, 2014, 05:27:15 PM

Title: A10s LINE IN impedance
Post by: kbro on June 18, 2014, 05:27:15 PM
I have an audio source plugged into the LINE IN on my A10s board, and the resulting digital audio is coming out sounding too quiet and lacking in tone colour (all men sound like Ed Milliband with a blocked nose; all women sound like Daffy Duck).

One avenue of attack I want to try to improve things is to match the impedance of the A10s to the audio source.  I already know the impedance of the source, but not the A10s Line In, so can someone please tell me what it is?  Or how to calculate it, or how to measure it (whacking a DMM across the jack didn't yield believable results!)

Please don't spend time telling me how to improve things by changing software or codecs or AC97 gain settings - I don't need any assistance in that area, thanks - it's just the electronics I need help with.  Thanks!
Title: Re: A10s LINE IN impedance
Post by: MBR on June 19, 2014, 03:12:33 AM
The impedance of liner-in should be around 10 kiloohms and it cannot be measured by normal multimeters, because they measure resistance using DC and you need AC (1 kHz or so) to measure impedance.

If you have an oscilloscope, try comparing singal of the audio source while plugged and unplugged to see if the line-in is loading the source too much. Or, alternatively, compare sampled waveform from A10 with another device (PC, laptop, etc), especially with some kind of Fourier transormation (the optimal signal for this is a .white noise).