So much noise

Troubleshooting and Support
1

Hi,

from a brand new daisy seed, I notice that just passing the input (yellow) buffer to the output (cyan) buffer in the main audio loop, I get crazy amount of noise

Is this normal operation ?

  • yes AGND is connected to DGND
  • I tried powering the daisy from usb 5V and I tried with a 9V transfo
    (I use the stlink to program it)

thanks for your help

image
image1672×783 131 KB

#include "daisy_seed.h"
#include "daisysp.h"
#include "arm_math.h"

using namespace daisy;
using namespace daisysp;

DaisySeed hardware;

#define WINDOW_SIZE 48

void AudioCallback(AudioHandle::InterleavingInputBuffer in,AudioHandle::InterleavingOutputBuffer out, size_t size)
{
    for(size_t i = 0; i < size; i += 2)
    {
        out[i+0] = in[i+0];
        out[i+1] = in[i+1];
    }
}

int main(void)
{
    hardware.Configure();
    hardware.Init();

    hardware.SetAudioBlockSize(WINDOW_SIZE);

    hardware.StartAudio(AudioCallback);

    for(;;)
    {
    }
}
2

I don’t have a scope handy right now, but it might be interesting to see what happens using an Oscillator object, to narrow this down to noise on input or output.

3

It seems we need to add an analog lowpass filter (at e.g. ~30 KHz corner freq), you can just use a 1-pole RC, I used .022 uF, 220 ohms. Still puzzling how filtering out the out-of-band signal can change the in-band signal.

4

yeah I though about R/C’ing the output, but I am surprized nobody noticed this beforehand

5

Many have noticed noise before.

6

After adding a 220ohms/22nF RC I get a better output but hiss is still noticeable (plugged into a guitar amp, especially when using a fuzz/dist pedal, it gets amplified)

should I use a second filter ? not sure how to figure the values though

image
image1626×950 176 KB

7

I tried with an osc, I get the same noise issue

#include "daisy_seed.h"
#include "daisysp.h"
#include "arm_math.h"

using namespace daisy;
using namespace daisysp;

DaisySeed hardware;
Oscillator osc;

#define WINDOW_SIZE 48

void AudioCallback(AudioHandle::InterleavingInputBuffer in,AudioHandle::InterleavingOutputBuffer out, size_t size)
{
    for(size_t i = 0; i < size; i += 2)
    {
        float sig = osc.Process();
        out[i+0] = sig/3; 
        out[i+1] = sig/3;
    }
}

int main(void)
{
    hardware.Configure();
    hardware.Init();

    float sample_rate = hardware.AudioSampleRate();
    osc.Init(sample_rate);
    osc.SetWaveform(Oscillator::WAVE_SIN);
    osc.SetAmp(0.5f);
    osc.SetFreq(670);

    hardware.SetAudioBlockSize(WINDOW_SIZE);

    hardware.StartAudio(AudioCallback);

    for(;;)
    {
    }
}
8

How are you wiring up your Seed? e.g. is it on a bread-board? maybe post a picture of your setup?

9

I noticed these spikes appear as I just have contact between the pc usb-c cable ground to the circuit

I have full gnd connecivity from there to the scope ground and the daisy ground

I added a 100nF and ferrite bead from the usb gnd, but the noise is still there

I migrated everything in a new aluminium box, same problem

at this point, any idea is welcome :slight_smile: