Audio Adaptor Boards for Teensy 3.x and Teensy 4.x

DOY38

Active member
Hello,
I would like use this card in my project, after reading the datasheet I can see on page 15 that I can have several sample rate from 8 to 96 kHz is it true ? Because on your site it is mentioned only 44.1 kHz. How it's works exactely when you like to change the sampling frequency ? With the with microprocessor ?
Thank you for your helps
Regards
 
The audio shield hardware can run at other sample rates.

All of the software is designed and tested for 44100 Hz. If you stray from that well worn path, the code may or may not work depending on a lot of factors. On Teensy 4 the sample rate is controlled by a dedicated PLL and clock dividers, so changing sample rates is easier (but still requires edits deep within the library code). On Teensy 3, the audio clock is created by dividing the system clock, which limits your choices.

Many people have successfully changed the sample rate. The finer details and issues have been discussed many times on this forum. Maybe you can find some of those conversations by search?

Some parts of the audio library software, like how WAV files are parsed and processed, may not automatically adapt. The audio library is a large collection of so many audio features, so there is no simple answer which coves all usage cases.
 
Hi Paul,
Thank you for your answer. I understand for the sample rate one point solved. In the datasheet, I can see so many gain Mix+6dB, AVC +12dB...So my question is what is the total gain of this component ? I need to acquire the sound from a hydrophone (is about -186 dB re 1V/µPa). I must know this gain (SGTL5000) to design my electronic board without going into programming details for the moment. In 'Features Analog Inputs' I can see 85 dB for ADC
so probably the gain is : k = 10^85/20 = 17782 ?

Thanks
 
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Is that a sensitivity of -186dBV for 1µPa, so -66dBV for 94dB SPL?
Or a signal level of -186dBV (0.5nV rms) ?

The SGTL5000 only has an input for an electret capsule microphone, not a hydrophone or any other kind of microphone. Its
definitely not a low noise preamp.

I'm pretty sure you need a suitable preamplifier.

Best to provide a link to the datasheet for the hydrophone and explain the signal more clearly - do you know the max rms voltage output
you need to handle? The minimum?
 
Is that a sensitivity of -186dBV for 1µPa, so -66dBV for 94dB SPL?

I'm not sure for this value, how did you find this value ? -186 dB re 1V/µPa is a caracteristic a feature of a Hydrophone not a dB SPL (the sound in the air). Sorry in my previous post I make a mistake : The maxi gain is for me is 40+22.5 = 62.5 dB (SPL)
 
Here it's the specification of the Hydrophone
1.png
 
Or a signal level of -186dBV (0.5nV rms) ?
Yes this value is possible I find for 50-100 dB re 1V/µPa about 0.03 nV - 0.1 mV with -180 dB re 1V/µPa. But the Topic is not about the Hydrophone right ? It's about the codec SGTL5000.
 
The information you've given on the hydrophone says nothing about its output impedance or whether its balanced/single-ended.
Apparently it records to an SDcard too?

Can you provide a link to the product page or datasheet? I can't click through that photo to find out more.
 
Hi,
Sorry I was doing something else. Yes I need to take the sound under sea and record to an SDcard. Don't worry about the hydrophone (electronic, impedance, single-ended etc...). My Topic is about the maxi gain of the SGTL5000 and nothing else. After reflexion and reading the datasheet I think the max gain of this component is 98.5 dB (40 dB+ 22dB + Mix (+6dB), AVC (+12dB), Bass Enhancement (+6dB) and Tone Control (+12 dB)). Am I wrong ?
 
Lumping EQ gain into the total gain makes little sense, unless you are happy to undo the EQ curve after sampling,
and you only need those frequencies. Anyway aren't the AVC and bass enhancement only on the output side, not input,
so are irrelevant.

There is 40dB + 22.5dB gain on the mic input, making 62.5dB gain with flat respose, and the datasheet is
_entirely silent_ about the microphone input noise performance. That's a big clue its poor. Probably very poor
as this is a low cost part (likely will be standard CMOS rather than a hybrid analog/digital process).

Basically the factor you seem to be completely ignoring (but which is usually dominant in microphone systems), is the noise floor
of the system, and to keep this low you need to know the source impedance, and thus the input noise figure of the
preamp for that source impedance. If the noise floor is too high adding gain cannot do anything(*). If we are still talking about
0.1mV full scale, the SGTL5000 can only raise the signal to 0.13V, and with an unknown amount of noise.

This is a microphone handling very low signal levels (100µV), and it likely needs a low noise microphone preamp to get good
signal-to-noise ratio.

Once you have a mic preamp boosting the signal to line level you don't have to worry about gain in the SGTL5000.

(*) Once the noise floor is more than a few LSBs you have all the useful information in the sampled signal in most
scenarios.
 
Hi,
Thank you about the Gain 62.5 dB, I understand better now. But I have a product that I took measurements on this electronic map
20220311_100006(1).jpg
After white wires I have the SGTL5000 and I guess the preamp is built into the hydrophone. With only 0.13V I think that there is another amplifier before the microprocessor with I2S ?
 
Hi,
Thank you about the Gain 62.5 dB, I understand better now. But I have a product that I took measurements on this electronic map
View attachment 27935
After white wires I have the SGTL5000 and I guess the preamp is built into the hydrophone. With only 0.13V I think that there is another amplifier before the microprocessor with I2S ?

The SNAP2 connects hydrophone to line-in of SGTL-5000

BTW,
if you wanted to build your own SNAP2 compatible recorder, simply use a Teensy with Audioboard, you only miss the display

Edit:
Hint: In order to see how David is doing it (for a different Recorder) have a look to https://github.com/loggerhead-instruments/LS1/blob/master/schematic/LS1.PDF
 
The SNAP2 connects hydrophone to line-in of SGTL-5000

BTW,
if you wanted to build your own SNAP2 compatible recorder, simply use a Teensy with Audioboard, you only miss the display

BTW ? What is it ? (ok By the way sorry for my English)
I don't think so, we have a HTI-96-min as Hydrophone and the sensibility is -180 dB re 1V/µPa and if I want to work between +2.5 Volts and -2.5 Volts, my gain (amplifier) is 2.5/0.1mV = 25,000 (88 dB). And with LINE-IN I have only 22.5 dB, are you sure of what you are saying? Is there an intermediate amplification stage ?
 
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Thus,
I missed a step, can you detail how to amplify with -180 dB re 1V/µPa (I'm working between 50 dB and 100 dB) and I have 0.3µV and 0.1 mV. How do you do ?
 
I only refer to the schematics SNAP(2) is using.
Depending on your application a SGTL5000 my not be suitable without additional amplification. Additional 20 dB may be useful for very quiet scenarios.
I suggest to check other user's publication to see how good SNAP is doing
 
Yes to add +20 is not as complicated as that. Can I have your electronic schematic please ? In your previous link for David 'LS1.PDF' I can see all components but without no connections. After reflection I uploaded the folder to the 'loggerhead-instruments/snap' I can see under Altium the electronic board with 'Loggerhead SNAP 2.21'
 
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Yes to add +20 is not as complicated as that. Can I have your electronic schematic please ? In your previous link for David 'LS1.PDF' I can see all components but without no connections. After reflection I uploaded the folder to the 'loggerhead-instruments/snap' I can see under Altium the electronic board with 'Loggerhead SNAP 2.21'

All connections are labelled. there is no need to connect equal labels with lines. AFAIK, this is the preferred style.
 
All connections are labelled. there is no need to connect equal labels with lines. AFAIK, this is the preferred style.

Yes you're right, after printing I can see this information (sorry I'm old school). After going through the folders I see this file what does it mean exactly? These are measurements made with Hydrophones
ClipLevel.jpg
Clip Level is probably the output of the SGTL5000 'IS2DOUT' ?
 
from figure 2 of https://www.nxp.com/docs/en/data-sheet/SGTL5000.pdf
you see that line-in goes to a 0 to 22.5 dB amplifier

so I would say, if you select SG = 0 for the sgtl5000 then you attenuate your line-in by -3.9 dB and therefore your clip level becomes 3.12 V and for a -180 dB sensitivity hydrophone (HTI-96-min) clip level is 183.9 dB. IOW, largest signal can be 183.9 dB // 1uPa.
on a 16 bit data precision 1 LSB is then 93.9 dB//1uPa (183.9 -90)
etc.etc
 
How do you find this value? After me : -3.9 dB = 20.log(Vs/Ve) -> Vs/Ve = 0.63. The value 3.12 V where it's come ?

b'cause 2V equiv to 0 dB as you can see from Table and which may depend on other settings of the SGTL5000
 
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