Teensy 4.0 Audio Shield - Line In Microphones

[AntiLoop]

Hi Alfred0, sorry to take into the thread,i'm experimenting the use of a cardioid microphone
at one of the 3 inputs of a cs42448 codec board ,ihave a good result with an amp.gain(5.0f)
wired to a mixer.gain(1,3.0),it's a prodipe TT1 mic.
the only trouble is a hum sound but low,surely a lack of impedance adaptation.

 

[Alfred0]

Hi Alfred0, sorry to take into the thread,i'm experimenting the use of a cardioid microphone
at one of the 3 inputs of a cs42448 codec board ,ihave a good result with an amp.gain(5.0f)
wired to a mixer.gain(1,3.0),it's a prodipe TT1 mic.
the only trouble is a hum sound but low,surely a lack of impedance adaptation.

Hi AntiLoop, no problem with the thread, is here for learning

I can´t remember properly, but I'm pretty sure that cardioid microphones mostly are dynamic microphones, they use electromagnetism to generate electric pulses that represent the sound that the membrane, which is connected to a magnet, captures, while condenser microphones needs additional power, know as phantom power, so in fact, cardioid microphones should have less problems to be use without any external power or amplifier, and that's why it should be working for you turning up the gain.

At least, that's my theory, also I don't know how cs42448 board works exactly, I suppose that is similar and the ports are line in/out, maybe it has some extra capabilities.

I'm talking from my limited knowledge in sound matter, one of the purposes behind this project was my self-growth in the audio field, trying to understand more deeply some concepts, so take what I said with a grain of salt. What I know is that if you can use an amplifier for your microphone, always is better ahahaha.

For now I'll try to pre-calculate the coefficients of my FIR filter and avoid the use of microphones doing a fixed system, maybe later in the future I'll fight a little bit more with the code and use the information that is being provided here to make it 100% active, but yes, the use of that kind of microphones could be a good trick to avoid external amplifiers.

 

[MarkT]

The sensitivity pattern of a microphone is due the the mechanical design mainly. Some condener mics are actually two diaphragms back-to-back that can be switch-selected to add or cancel to provide several different patterns.

 

[AntiLoop]

maybe you can take a look at those systems fitted in comfort headphones or earphones,to eliminate
all noises coming from outside,they certainly use dedicated microphones with a dephasing algorythm

 

[Alfred0]

maybe you can take a look at those systems fitted in comfort headphones or earphones,to eliminate
all noises coming from outside,they certainly use dedicated microphones with a dephasing algorythm

Yes, the concept is the same, I've testing with some precalculated coefficients in MatLab using FX-LMS algorithm and seems kind of working, is not clear.

Due to the deadline I had, I can't do more now, so the new deadline is for January, I'll check the library trick that Paul mention previously and see if is possible to make some analysis block capable of doing the FX-LMS efficiently so the system becomes active like those headphones.

I think that could be pretty useful even for other purposes, like making a filter for your inputs to denoise mics, because you can use samples of the noise, so they could be load in a microSD and you can select which type you want to apply.

I really think Teensy board is capable of doing a lot.

When I get better samples from my tests with the actual system I'll share some recording of the results, is really surprising how well it works when it works.