USB Audio-Input [UAC1] : Strange signal behavior

[kuteleco]

Hi,

our team is developing a signal acquisition device that is capable of connecting to an Android smartphone. We have done tests with models from other manufacturers without problems but we are having some troubles with the newest Samsung Models as we are having different results.

For example, the Samsung Galaxy Tab S2 (SM-T713) model works correctly but with both the S10 family and  the Galaxy A70, we are seeing changes in acquired signals. As we can see in the first image, when using a square signal as input captured by different smartphone models, we can see that in the last case (corresponding to Galaxy S10 and A70) the correct signal is not obtained:

Image 1 - comparison of the acquisition of the same square signal with different smartphones

It is as if a high pass filter was applied. Which can be seen in the following image by increasing the frequency periodically (10 Hz after 10sec., starting at 20Hz) and maintaining the amplitude:

Image 2 - 10 Hz increment every 10 seconds, starting at 20 Hz

I have seen some posts referring to problems with the use of external USB audio output peripheral that have been solved. But I have found almost no case regarding to input/adquisition problems. That is why I would like to ask you if there is any workarround or change in the system settings in the newest models. In order to avoid any type of alteration/filtering of the incoming audio signals by the USB.

My best regards.

[AntS]

Hi @kuteleco , 

I've asked our software team about this to see if they can shed any light on it and have any advice - and me or one of the other Moderators will let you know what they say.

Meanwhile, if anyone else out there has some expert insight, definitely please share!

[AntS]

Hi @kuteleco ,

We've had a reply back on this one.

Our developement team carried out a similar test on a Note10 and USB Type C earphone by using square signal, but weren't able to replicate the same phenomenon. They've advised that the issue is likely to be in the specific Samsung devices you're using or in the device you're developing.