Works out of box but with distortion on notes

Peter posted Oct 4 '16, 17:12:

Joseph, what a wonderful project you've put together here, been looking for something like this for ages!

Just programed an sd card and put it into a RP3, using the piano samples on here. Works out the box but there is quite a bit of distortion / noise with each note played? Can this be fixed as I don't have a dac just yet.
Thanks Pete

Jon posted Oct 5 '16, 07:09:

Do you get distortion if you use aplay to play one of the samples?

To try this out, login to sampler box username root, password root and cd to wherever your samples are, then run

aplay somesample.wav

If that's distorted too then my guess would be you would need to find a way to reduce the output level from the sound device that is feeding your amp or headphones. You could try the midi volume control patch described elsewhere on the forum or try alsamixer (sorry not used it myself, you'd have to search for the details).

Hope this is enough to get you unstuck.


Glen posted Oct 7 '16, 03:34:

I also have an RPi3. It works out of the box for me, with no (detectable to me) distortion using the audio out jack on the RPi3 or a USB-DAC.

Peter posted Oct 7 '16, 23:04:

Hey Jon! thanks for the tip using aplay...I was able to reproduce the noise... its actually sounds more like white noise that accompanies the note during the last few seconds of the decay... I've had a play with alsamixer volume control, and noted the noise present at the loudest and quietest settings on my RP3, both through my headphones an amp.

@Glen, i had a DAC and this worked perfect until the usb connector broke now trying to make the setup work out of the box.. thanks

Jon posted Oct 20 '16, 07:19:

Hmm, well that's kind of odd. Its hard to diagnose what's wrong with a sound without even hearing it, but from what you describe it sounds like there's perhaps a compressor or an automatic gain control somewhere which is turning up the gain (causing more white noise) as the amplitude (loudness) of the sample decreases.
Where the compressor could be I can only guess.
It could have been present when the original sample was recorded - try a different sample set and see if you get the same thing or not.
It could be in your amp, although this sounds less likely if it worked fine via the DAC.
Its possible that there's something in the software part of the audio chain - maybe even in alsamixer, although I am guessing completely, as I've not tried it myself.

Josh posted Oct 20 '16, 12:22:

This sounds to me like a hardware fault. Many cheap MP3 players have the same problem. My advice would be to get a DAC (one thing: there are many DACs with a built-in volume control. I would consider getting one of them).


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