Teensy's low pass frequency response

[Sequoia101]

Hi guys!

I'm building a guitar pedal with a Teensy 4.0 and an Audio Shield and I came to realize that, even without any processing block, it acts like a low pass. This introduces a lot of mud into the guitar sound and distorts low frequencies.

This is the audio spectrum obtained in Audacity from a song I recorded using the Teensy without any processing block.

Is there anything I can do to correct this? Is this normal?

[Mcu32]

Hi guys!

I'm building a guitar pedal with a Teensy 4.0 and an Audio Shield and I came to realize that, even without any processing block, it acts like a low pass. This introduces a lot of mud into the guitar sound and distorts low frequencies.

This is the audio spectrum obtained in Audacity from a song I recorded using the Teensy without any processing block.

Is there anything I can do to correct this? Is this normal?

Your song is probably not very similar to https://en.wikipedia.org/wiki/White_noise Only in this case you would see a more linear spectrum.

[Mcu32]

If you search the forum, you can find audio-shield spectrum plots.

[Sequoia101]

Your song is probably not very similar to https://en.wikipedia.org/wiki/White_noise Only in this case you would see a more linear spectrum.

Well any song will produce a spectrum like this one. Whenever I play my 6th string (the lowest one), the sound heavily distorts.

[Mcu32]

Well any song will produce a spectrum like this one. Whenever I play my 6th string (the lowest one), the sound heavily distorts.

?? Any song you record is not white noise. Not sure what you're trying to say. A recorded song will *never* show a linear spectrum.
Distortions may caused by too high input level?

[Mcu32]

Also, keep in mind that the shield is consumer quality. But it's quite ok.

[Sequoia101]

?? Any song you record is not white noise. Not sure what you're trying to say. A recorded song will *never* show a linear spectrum.
Distortions may caused by too high input level?

Right, but it will rarely show this kind of low pass response. If I reduce the level of input the high frequencies become barely audible. I have no way to test it with white noise now but I will when I can.

[Mcu32]

Well, the shield is not as bad as your plot shows. There is something wrong. But you simply can't judge that from a song.
Do you use the linear input? (not mic)


The user blackadr made a quite good board. I've used it (well, a modification by myself)

http://blackaddr.com/products/

[Mcu32]

Here's an article about self-noise : http://openaudio.blogspot.com/2017/0...elf-noise.html