- Edited
Hi everyone and @giuliomoro ,
It has been a long time that I decide to not focus on getting a clean signal from bela. But since my instrument is getting more into profesional level, I have been working together with an electronic engineer student in order to eliminate this problem. I am using 4 piezo mics with this circuit connected to the Analogue inputs from Bela
After measuring the noise, We decided to try to work on the possible items:
1 - To get a clean ground with a customized battery pack
2 - To design a preamp for these type of mic (this preamp also has biasing circuit, whereas the circuit in the bela post mentioned become not necessary anymore, since I would be biasing twice)
After working in these items for a while, we are a bit upset to realize the noise is still here, as you can see in this oscilloscope (the signal and the bela output). We measured this noise a signal of 2.7kHz of 32 dB signal to noise ratio:
In the code, I am always using sc code to send the signal from a synthdef:
(
SynthDef("help-AnalogIn",{ arg out=0;
var mic, ampli, freq, hasFreq, sin, flatn, fft,zerox,pitch;
// mic = SoundIn.ar(4,3);
var in1 = LPF.ar(LeakDC.ar(SoundIn.ar(2,1)),1000); // To make this easier we first perform some signal conditioning and smoothing to the signal (DC offset filter, full wave rectification and a moving average filter).
Out.ar([0,1], in1));
}).send(s);
);
s.sync;
Synth.new("help-AnalogIn", target: s);
I am start to wonder that this system is beyond my capabilities to solve myself, since it seems to be a digital problem. Any ideas how to solve this problem?