Sound distorsion - update v0.12.X

[GoodSpeed001]

Hello,

After last updates v0.12.0 and v0.12.1 the sound when using Soundfonts is distorted.

I'm currently using Pi3B with chris-jh mt32-pi-midi-hat with PCM5102A DAC (specific GY-PCM5102 ) if I lower MT32-Pi versions the same does not occurs.

Also I have tried to lower the sample rate to 44100, use the new Soundfont config file to the specific Soundfont (Roland_SC-55_v3.7.sf2 from archive.org), to help troubleshoot I have attached my current config (mt32-pi.cfg).

mt32-pi.zip

If I use the same Soundfont in Soundfont Midi Player 6.1.1 (https://falcosoft.hu/softwares.html) the audio isn't distorted.

When possible, please confirm or point me to a possible solution, I have tried a couple of config's and can not figure out a solution. :(

With my best regards,

GS

[dwhinham]

How are you updating / "lowering the versions"?

Wipe the SD card and do a full reinstallation of ALL files from the latest release. Firmware files have been updated recently.

[dwhinham]

it's possible to instead of having the auto detection of I2C DAC, can we have the ability to select? like something Auto | I2C PCM5102A | PCM5122 or other?

This will not help anything and there's no reason to bring it back. The PCM5102 is a "dumb" DAC with nothing to detect, it cannot accept commands, and it can't be communicated with. It requires zero special setup, it just accepts audio samples from the Pi, and converts them to analogue audio. That's it.

mt32-pi will probe for the "intelligent" DACs on startup, and if nothing is detected, it will continue on as normal, assuming a "dumb" DAC. Your DAC does not need any initialization, and like I say, I am using the same model of DAC chip here on multiple different pieces of hardware for years without any problems.

Make sure ALL the solder pads on the GY-PCM5102 are correctly soldered. Otherwise, replace it with another module and try again - these modules are very cheaply made and it could easily be faulty.

[GoodSpeed001]

Hi dwhinham,

Regarding the selection of DAC additional config etc, understand.

I've been doing exhaustive tests and various combinations and I've come to the conclusion that the problem is in the audio volume.

First I started by verifying that I had correctly configured the DAC at the hardware level, as indicated in your guide.

Then I did the Debug, following the Troubleshooting guide, I didn't get any errors.

I tested several options at the configuration file level ( mt32-pi.cfg ), Audio Options - output_device = i2s or pwm, reduced the sample_rate from 48000 to 44100, and I came to the conclusion that the problem may be in the DAC.

This is because if I use output_device pwm I don't have audio distortion.

But I'm confused, is there a possibility to reduce the audio volume via the configuration file?

If you reduce the volume via buttons the problem does not appear. Or my issue is it really a problem with the DAC?

Regards,

GS

[dwhinham]

What is gain set to in the fluidsynth section? The default is 0.2 as recommended by FluidSynth, so any higher is going to risk distortion.

Note that this can also be overridden in SoundFont .cfg files.

You can turn the volume down by adjusting the gain setting, e.g. gain = 0.16 would make it 80% of the original volume.

If it's not this, it sounds like you have a hardware issue.

[GoodSpeed001]

once again thank you dwhinham.

I try to check if it solves, otherwise I'll replace the DAC :)

Regards,

GS

[GoodSpeed001]

Hi dwhinham,

All the issues I have reported been solved with version v0.13.0 (also tested with v0.13.1) no issues :)

Now all my MIDI's files play without no issue or sound distorted, if necessary I can provide theme as well my mt32-pi.cfg for testing purposes.

Regards,
GS