Audio Input feedback

[Daniel Lawler]

Hello!

I am attempting to connect Jan Ostman's Minipops clone to a Pro Micro running Mozzi, using the Audio_input.ino example.

From the minipops I have a generic AUX cable running to my Pro Micro connected on pin A0, with another audio out connected to pin 9 for audio out. 

The problem I'm having is that on start, the audio does not have any high frequency (very low registered sounds) and then progressively the high "Gets higher" until you can hear the full frequency, but also with a very high frequency "feedback" sound.

I've tried a few different methods like Low Pass Filters as well as a small cap setup similar to what I'm using in the minipops to no avail. I know it's not the Minipops directly because I've run that for a large amount of time with no increasing issues.

Any idea what's wrong here?

[Daniel Lawler]

Apologies as it did not like my original post with images. I'll post them here. 

Here's a simple drawing schematic of the mini-pops:

And here's a basic mockup of my current setup:

[Daniel Lawler]

Small update here - I did try the output circuit as outlined here (both input and output, separately and together as I saw someone on here mention similar problems), but this still produced the whine. 

[tomco...@live.fr]

Hei,

Maybe I did not understand very well your schematics, but how exactly did you connect the Minipops to Mozzi? The audio input for Mozzi should be in the right range (0 - 5V for Arduino mini), otherwise you need to biased it. As the minipops is also a MCU is should be straight out of the box in the correct range. Is there any decoupling capacitors somewhere?

[tomco...@live.fr]

Thinking again about it, it might be an aliasing problem. Do you have access to a scope to have a look at the signal (filtered) you are inputting in Mozzi?

[Daniel Lawler]

I am a bit green behind the ears, so after a bit of googling, I don't believe there's any decoupling capacitors in use. There is one capacitor on the audio out line from the minipops and I've also tested a few in the same fashion going into the Pro Micro. 

As for your first question, I am just using a standard AUX cable to connect the two (from audio out to audio in).

Unfortunately, I do not have access to a scope. I have tried a few anti aliasing circuits to filter the audio, but wasn't able to get anything in range to filter out the noise (I tried a few different ranges of resistors etc)