Output clean or with noises?

#1

I have done tests The eardrum works well in general with the parameters for gain, volume, and configuration of microphone inputs.
But with these different settings, the “Tympan” makes noises. The output audio signals are not clean on an HP output simulation resistor.
It’s disappointing.

I have a Microchip card named Starter Dspic (reference DM330011). These audio output signals are clean.
Then I made an analog card with an expander - audio compressor. It makes much less noise.
what could be done to improve the output sound quality?
Otherwise we could validate the other “line” audio outputs? For example: “LOL and ROL” located on pines 26 and 27.

#2

Hi Morel!

I’d like to help you with your noise issues. Can you answer a few questions?

  • Which input were you using when measuring the output noise? If you were using the microphone jack, did you have anything plugged in?

  • If you were using a resistor in place of headphones, what did you connect to record the noise that are reporting?

  • Which software was running on the Tympan? (The default software has a lot gain, like a hearing aid, which will make noise more apparent)

I definitely want to help out, so please let me know!

Chip

#3

Which input were you using when measuring the output noise? If you were using the microphone jack, did you have anything plugged in?
My reply: In is 1 Generator Freq. set to 625 hertz + headphone amplifier.

If you were using a resistor in place of headphones, what did you connect to record the noise that are reporting?
My reply: I have already tested several microphones (two TYMPAN MEMS microphones included). It does not change anything of quality.
The HP output is connected to a 330-ohm load and connected to the oscilloscope. I will send you pictures of my tets by mail.

Which software was running on the Tympan? (The default software has a lot gain, like a hearing aid, which will make noise more apparent)
My reply: I made a small change of parameters just for sensitivity and volume.
For more info, you have an e-mail to come.