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  1. Replies
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    Hi Corbee, thanks for the link (although that...

    Hi Corbee,

    thanks for the link (although that link is probably breaking a copyright)!

    My preamp is exactly that circuit except for the following changes:

    * C4 and C7 is 100pF --> gives a...
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    hi CorBee, hi all! very nice progress! I...

    hi CorBee, hi all!

    very nice progress!

    I have some comments on some of the posts made in the last days:

    * sample rate: please note that in order to really accurately identify a large part...
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    @CorBee: I do not know exactly, but I think...

    @CorBee:

    I do not know exactly, but I think you should also use the AGND when using the audio board.

    One thing I thought about was the follwoing: You have the preamp already in the audio...
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    Hi Walter, thanks for the clarification and...

    Hi Walter,

    thanks for the clarification and the info on Vdd, input resistor and dB (A) measurements! Thats very helpful! I will take out the input resistor, your comment solves that long-standing...
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    Thanks for the suggestion! But as I wrote,...

    Thanks for the suggestion!

    But as I wrote, more gain does not mean more SNR, but less. And potentially using the 5V from the USB means even more noise coming in.

    Here is my setup (from right to...
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    Hi, made some more experiments with the...

    Hi,

    made some more experiments with the ultrasound MEMS microphone SPU0410LR5H-QB and the mentioned ELV microphone preamp:

    - I used the original schematics of the preamp, but changed the...
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    Teensy 3V3 -----2K2---2K2---Pre-amp/Mic 3V3 ...

    Teensy 3V3 -----2K2---2K2---Pre-amp/Mic 3V3
    | |

    10F 10F
    | |
    GND GND
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    Also corresponds with my observations. You could...

    Also corresponds with my observations. You could also filter the 3.3V from the Teensy with a series 2K2 resistor, a 10F cap to GND, then another 2K2 series resistor and another 10F to GND. But...
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    I am not a specialist in OP amps, so I do not...

    I am not a specialist in OP amps, so I do not know what a slew rate is . . .

    You can find the schematics in an old ELV journal article under the link above (you have to pay 50ct for it, so I cant...
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    Hi Cor, hi Foaly, thanks a lot for the hint on...

    Hi Cor, hi Foaly,

    thanks a lot for the hint on availability of the mic at ELV!

    I ordered a bunch and made some experiments. I used the SMD-mic preamp also available at ELV
    ...
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    Hi Foaly, looks like you are making progress...

    Hi Foaly,

    looks like you are making progress fast!

    Could you explain your downsampling a little bit more? I fail to understand what you are doing in your code. As I have understood it,...
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    Yes, you are right, the data sheet allows up to...

    Yes, you are right, the data sheet allows up to 96kHz. At the moment I overclock mine as high as 234ksps for FM wideband reception ;-). But that is not recommended, because it could damage the chip!?...
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    Hi Foaly, it would be absolutely awesome to...

    Hi Foaly,

    it would be absolutely awesome to have someone program pitch shifting/phase vocoder!

    But for your goal, I think you could have it much easier ;-).

    Two years ago, I programmed a bat...
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    Hi Foaly, I think you are definitely on the...

    Hi Foaly,

    I think you are definitely on the right track. You need to use floating point, one of the new versions of the CMSIS library and maybe Brians Convolution filter routine (which already has...
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