Distortion with some VS1053 instruments playing high notes

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Joined: Mon 2015-08-24 5:25

Distortion with some VS1053 instruments playing high notes

Post by Davidelvig »

I have a VS1053 chip on my board, playing well in all respect except:
- on certain instruments (trumpet, MIDI Program 56) and others to some degree, I get distortion on higher notes.

I'm sending MIDI through SPI to the chip.
No other audio or data inputs.
Output is through a headphone, or in this case, a desktop speaker. Same result - distortion on the high notes.
MIDI velocity is 50.

I've testing with another product (with another vendor's synth chip) and do not hear distortion.

I've create a video demonstrating the problem.
- It this a known issue?
- is there a fix?
- what else can I send to help diagnose it?

VS1053 Distortion.mp4
(37.04 MiB) Downloaded 24 times
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Re: Distortion with some VS1053 instruments playing high notes

Post by pasi »

Distortion related to a specific instrument is probably due to how the instrument's synthesis is implemented.

Trumpets seem to use saw-wave and lowpasses, the saw-wave intentionally generating harmonics, so it is not surprising that those harmonics will somewhat alias with the higher notes.

Can you transpose those problematic notes or map the instrument to a different instrument?

The vs1053b rtmidi app fixes an issue with handclap, see: http://www.vlsi.fi/en/support/software/ ... tions.html
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