Mod to programmatically disable speaker whine/hiss.

Macaba

Hi all,

I've been working on porting the Teensy Audio Library to M5Stack to allow full (& easy) audio synthesis.

However the background whine/hiss from the speaker when no audio is being played is very annoying (and quite loud on my M5Stack).

My suggested modification in this case is to put a wire from Pin 1 of the speaker amplifer to GPIO5.

Then it's just a simple case of digitalWrite(5, HIGH); to turn on the amplifier, and digitalWrite(5, LOW); to turn off the amplifier.

There seems to be a 30-100ms delay for the amplifier to turn on, and very little delay for it to turn off so I sadly can't get my audio library to automatically turn the amplifier on/off because I would miss the beginning of any new audio playback.

So I've just attached the amplifier control to BtnA for manual control so I can at least turn off the noise.

Good luck to anyone else attempting this mod! :)

cbrightly

@macaba I will have to look into this! Do you plan on sharing any of your work porting the audio libraries from the Teensy over to the M5Stack / ESP32?

Macaba

Yep! It'll be going on GitHub at some point.

It won't be compatible with the the original audio objects from the Teensy library;

I've moved over to float datatype for audio samples (it makes certain audio algorithms so much easier) so I've been slowly porting across the objects when I use them.
I've added some functionality that lets you get more detailed CPU reporting.

You can see my handy 'Amp on/off' control now:
0_1539868916364_adaacef8-3324-46f7-a94e-ae38e249f3e7-image.png

Macaba

@cbrightly https://github.com/macaba/ESP32AudioLibrary

Initial commit of ESP32/M5Stack audio library done. Not that many objects yet, I'll be adding more as time allows.

ChrisMicro

Hello, I just flashed it and it works. Thankx :-)
Do you use a software sigma-delta-DAC or the internal 8 Bit DAC?
Probably you can add a second example which shows a little bit of the sound qualities of the lib.

Calin

You can mute the speaker very easy from code.
Just call
dacWrite (25,0);

PlayTheGame

@Calin Hold your ear on the "mute" speaker. There is still noise with your code.

THX for the hardware mod suggestion.

Nifkuzyaire

Hello,
Maybe you can port this teensy dalek voice sketch to m5stack
Thank you in advance.

https://pastebin.com/dYf49wp5

masrodjie

@macaba Nice. I was trying all the way to avoid noise on speaker and none of luck. Then trying using this method and it's works! Thanks

funghy

It is probably better not to connect PIN 1 of the NS4148 but pin 3 the buck converter EA3036 to pin 5 since otherwise you have a bigger power consumption. You could also remove R23 in that case.