How to get audio running on the CM3 and amplify the audio signals please??

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Joshua_S
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Joined: Mon Mar 19, 2018 3:32 am

How to get audio running on the CM3 and amplify the audio signals please??

Post by Joshua_S »

Hi guys,
:mrgreen:
Trying to get audio running on the CM3 using GPIO40(PWM0) & 45 (PWM1) and convert the stereo output into a Mono output.
Then I want to amplify the audio signals using an differential amp op circuit whilst using a potentiometer (pot) to control the volume (gain) which will be pushed into a 3.5mm headphone jack when a headphone is plugged in, else it will reroute the signal to a speaker if nothing is plugged in.

Following advice from an article of Kynix Semiconductor Electronic Blog http://www.apogeeweb.net/ I managed to figure out what amp op and differential amp op were. but when creating my circuit I was then plagued with the output of my audio signals being too low (10MA) to be able to register any sound.

I then thought I should look into having an power amp added to the circuit design. Now I don't know whether my circuit would be able to just output the audio signal as mono if I simply change the differential amp op chip to slightly higher output; however I have no clue as to what chips would be better or what level of MA I need to aim for to output the mono sound into the headphone/speaker. Or I have to add in a power amp on the end/before my circuit or replace the amp op chip with a singular power amp op chip.

My current schematic is as such:

Image

I've got a 50k Pot in my prior design would this work better for the circuit? Or will have to add on additional 15K resistor just to attenuate the signal?

The audio_right is following the below schematic that a buddy of mine showed me. I asked whether or not the line on its own would be used for anything and he said to simply Ground it.

Image

The power supply arrangement is using the 5V to power the entire design which I intend to stick to as much as possible considering the rest of my design is all being powered off 5v.

Image

I've seen output decoupling talked about a little online but I've not got a full clear understanding what that is. So will look into it if its needed in the project. I'm assuming there would be a way to change the voltage up from 5v to 6v to run LM386.

By the way, do you guys have any recommendations for a 5V to 6V boost converter? I see alot of circuits online as 5v to 12v, 3V to 9V and 6V Step down 5V regulator but haven't found anything for 5V to 6V or am I missing something?

Many thanks.
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mediatechnology
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Location: Oak Cliff, Texas
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Re: How to get audio running on the CM3 and amplify the audio signals please??

Post by mediatechnology »

The LM386 will run on 5V.
4V is the minimum.
Have a look at the datasheet: http://www.ti.com/lit/ds/symlink/lm386.pdf

What is a CM3?
The circuit in the middle is a variable gain circuit ranging from -1 to +1.
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