[AudioI] Microphone connector gain?

[Ron Patton]

Hi Matt,

Yep, it was a bug in my application.   There is plenty of gain available 
to drive the device the Zero is integrated in to.

73,
Ron / W4MMP

On 1/5/2021 04:40, Matt wrote:
> Good news, hope that was the problem !
>
> On 5/1/21 5:29 am, Ron Patton wrote:
>> Hi Matt,
>>
>> Thanks for the information and verifying that my configuration is
>> correct.   I think I may have found the problem and it was in my
>> application.  The application has a quasi gain control (it simply
>> reduces the microphone volume applied to the Portaudio call back that
>> drives the Zero).   The routine was not correctly calculating the volume
>> level.   More testing is needed and I will let you know the results.
>>
>> 73,
>> Ron / W4MMP
>>
>> On 1/3/2021 22:59, Matt wrote:
>>> On 4/1/21 4:55 am, Ron Patton wrote:
>>>> Hi Folks,
>>>>
>>>> Any takers on this?
>>>>
>>>> 73,
>>>> Ron / W4MMP
>>>>
>>>> On 1/1/2021 23:07, Ron Patton via People wrote:
>>>>> Hi,
>>>>>
>>>>> I am using the AudioInjector Zero in a hardware project (an Amateur
>>>>> radio transceiver).   The Zero is working well for audio output.
>>>>> However the microphone input of the Zero does not appear to have the
>>>>> gain needed for using a standard run of the mill computer headset.
>>>>> Now, I'm not an audio expert by any means so some of the following might
>>>>> not be correct (or actually stupid). But,  my assumption is a standard
>>>>> computer headset uses an electret microphone element.  These need a
>>>>> "bias" voltage to operate properly.   I have measured the voltage at the
>>>>> Zero microphone connection and it is supplying ~2.5V which should be
>>>>> sufficient.  OK, so far so good.   However, the Zero does not seem to
>>>>> provide enough gain and the audio volume is a bit low.
>>>>>
>>>>> There are two things I have done to examine the issue.
>>>>>
>>>>> 1) Attached is the ALSA configure used to configure the Zero.  It is the
>>>>> file supplied when installing the test routines supplied by
>>>>> AudioInjector.  It is attached to this email.  It is applied before
>>>>> starting the application that uses the Zero (via Portaudio).
>>>>>
>>>>> 2) I have used ALSAMIXER to adjust the values that it displays (Mic
>>>>> Boost and Capture).  These have been set to 100.  (Screen capture attached).
>>>>>
>>>>> So, the question is:  Is there something I can configure in ALSA (in the
>>>>> attached asound.state.MIC.thru.test file) or otherwise to raise the gain
>>>>> of the microphone connection?
>>> Hi Ron,
>>>
>>> It looks like the mixer is set correctly for the microphone. In the
>>> playback section, the input mux is set to microphone. The capture is set
>>> to microphone. You should have plenty of gain on the mic.
>>>
>>> The microphone connector is the through hole capacitor looking footprint
>>> on the board. It isn't the stereo input connector. I can see that you
>>> measured the voltage on the microphone connector and that looks right.
>>>
>>> There are some tests you can do with alsa mixer. One test I can think of
>>> will connect the microphone mixer directly to the analogue output of the
>>> audio codec. Enable the "Output Mixer Mic Sidetone Switch" and check
>>> that you can hear the microphone on the output of the sound card.
>>>
>>> Also triple check that the GND and signal lines of the headset
>>> microphone are correctly connected.
>>>
>>> Matt
>>>
>>>
>>>>> --
>>>>> 73,
>>>>> Ron / W4MMP
>>>>>
>>>>>
>>>>> --
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