I'm using SSM2518 hooked to a pair of 8ohm GO2014C4Y8GD-2 speakers. We have I attached to an I2S peripheral on an ST microcontroller. The audio output works fine but there is always a large amount of output noise coming through the speakers.
This noise is more audible if we send all zero i2s samples. Noise is present in soft mute mode while sending all zero samples.
Is this just normal chip performance? or can this be due to some other factor.
Stuff we checked.
Clock jitter on MCLK (looks good below what is recommended on the datasheet of the ssm2518)
Supply line noise (also looks good)
Adding a capacitor and a FBead on the output (no difference...)
We are running out of ideas.
I have attached a recording with a microphone placed at 1cm from the speaker. The recording is loud, the real perception of the audio signal is more quiet (still annoying). I've also attached an FFT for the same signal.