The way I read post #9, it only mentioned the output impedance, but not its cause. Then again, I haven't read the link of post #9.
The preamplifier in post #97 of the thread I linked to is meant for bird and frog sounds. I don't know if those are in the same frequency range as lung sounds, if not, you have to modify the built-in high-pass filter.
The preamplifier in post #97 of the thread I linked to is meant for bird and frog sounds. I don't know if those are in the same frequency range as lung sounds, if not, you have to modify the built-in high-pass filter.
Is this the circuit you are referring to, Mooly? I shall connect the ring to 5V DC, right? And the same cable must connect the 2.2kOhms to the positive pin of the capsule? Similar with 2.2uF capacitor, it shall be connected to the tip and the tip must be connected to +Signal?
Yes, its a very generic circuit applicable to these sort of capsules. The signal level is still low remember, it is not a line level type output and still needs amplification.
With the same configuration, this is the recorded audio using Audacity. The remaining are just mere static noises.
I'll try to configure this circuit and see if I can troubleshoot the problem.
The pinout of the connector is different from what PRR wrote in the bird sound thread.
https://www.diyaudio.com/community/threads/need-advice-for-a-weird-project.352655/#post-6159191
Maybe that's why it doesn't work.
Why not try your preamp with a known good source first, then concentrate on the capsule.
If you make a potential divider from two resistors of say 10k and 100 ohm then that would give you something like the level the capsule would give if you feed the divider with a line level signal. You could then feed that into the preamp and check you get line level back out.
Good day! I disregarded the LM386 pre-made module (picture on the first post) and made a circuit from scratch (will share the schematic soon).
The output is directed to a laptop audio port via a TRRS plug. There is only minimal noise by replacing the battery source with cells instead of USB port of the laptop. The snippet of recording using Audacity is shown below.
The only remaining problem now is that, even if the gain of LM386 is set to approximately 200 and the volume is adjusted to distortion less amount, the ECM cannot pick up any lung sounds even with a coupler attached to it.
Hi,
What do you call a coupler?
As Whitedragon (and i) said you'll probably need a stethoscope to put your capsule on.
What do you call a coupler?
As Whitedragon (and i) said you'll probably need a stethoscope to put your capsule on.
Not entirely okay tho 🙁 the static/ground noise is loud. Attached also here is the recording with normal voice 30 cm away from the microphone.
https://voca.ro/1aX4AEQ7zCNx
A mic coupler forms the air chamber on which the sound waves travel on to the microphone. I have managed to create a somehow feasible coupler.
Photo courtesy of J Winkler: https://mspace.lib.umanitoba.ca/bit...effrey.pdf?sequence=7#page=95&zoom=100,92,124
I've made a similar coupler and the recording seems to capture the sound but there is a noise. https://voca.ro/1j50HkQEIz1t
The recording device seems to have some form of automatic gain control in your sample. When you are not talking the gain goes very high and that is why you hear the noise:
https://en.wikipedia.org/wiki/Automatic_gain_control
Just a random thought... would using an amplifiers phono stage, even a moving coil stage give better noise free amplification for really low level sound? Maybe the RIAA response wouldn't matter for the intended use.
https://en.wikipedia.org/wiki/Automatic_gain_control
Just a random thought... would using an amplifiers phono stage, even a moving coil stage give better noise free amplification for really low level sound? Maybe the RIAA response wouldn't matter for the intended use.
Please do, a schematic could be very helpful. It doesn't have to be pretty, just readable.
Honestly, I am not familiar with this concept Mooly. But thank you for your insights, would you care to enlighten me?
Here it is, sorry for providing a rush work.
Attachments
An audio amplifier (or preamp) with a phono stage is a high gain low noise amp. The Moving Coil input is very sensitive (very high gain) but with low noise. It was just an idea. You would still need to bias the capsule (as you show in post #22) and feed that to the phono input.
Is that 5 V source a battery, a laptop USB port or something else? There is only some 12 dB of suppression from that voltage source to the microphone capsule output signal (just the voltage division of your resistive voltage divider), so it is essential that it is a very clean 5 V. In the bird sound project, we used several sections of brute-force RC low-pass filtering to clean it up.
This is noted, Mooly! Thank you
I've used a laptop USB port initially, the noise was much bigger. In this recordings I provided above, I am currently using a 6V power series, with four 1.5V batteries in series. Unfortunately, the noise is still large.
Hi,
On the last example you linked on #30 message the repeating noise sound like a digital polluted supply rail to me.
The sound from the capsule/ coupler is indeed relatively low but sound 'clean', it is an encouraging thing. 👍
Advice given by Marcel about psu filtering hold for your 386 circuit too.
How do you supply the 386 circuit? Edit: as in your schemo: powered by the 6v cells?
Is this circuit shielded (it could be picking EMI/RFI)?
What adc ( converter) do you use? Mic input on a laptop? If it is then try to run the laptop on battery it might solve the issue.
Said otherwise it could be a ground issue too on computer side. Been there even with 'pro' soundcards...
Thank you putting Vocaroo's service to my knowledge, seems fine and handy!
Edit: i listened to the mic 'check hello' file. There is definitely some agc taking place: computer using windows? There might be a software running hidden to perform some 'expanding ( dynamic) treatment'. Time to seek and desactivate any windows (or integrated to your soundcard sotware suit) integrated software enhancer.
Otherwise it sound nice to me ( as a mic capsule should sound!).
You are not that far away, keep investigate, it will pay off!
On the last example you linked on #30 message the repeating noise sound like a digital polluted supply rail to me.
The sound from the capsule/ coupler is indeed relatively low but sound 'clean', it is an encouraging thing. 👍
Advice given by Marcel about psu filtering hold for your 386 circuit too.
How do you supply the 386 circuit? Edit: as in your schemo: powered by the 6v cells?
Is this circuit shielded (it could be picking EMI/RFI)?
What adc ( converter) do you use? Mic input on a laptop? If it is then try to run the laptop on battery it might solve the issue.
Said otherwise it could be a ground issue too on computer side. Been there even with 'pro' soundcards...
Thank you putting Vocaroo's service to my knowledge, seems fine and handy!
Edit: i listened to the mic 'check hello' file. There is definitely some agc taking place: computer using windows? There might be a software running hidden to perform some 'expanding ( dynamic) treatment'. Time to seek and desactivate any windows (or integrated to your soundcard sotware suit) integrated software enhancer.
Otherwise it sound nice to me ( as a mic capsule should sound!).
You are not that far away, keep investigate, it will pay off!
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