Quality of the Raspberry Pi onboard sound

A long time ago I had a look on the Raspberry Pi onboard sound on the oscilloscope. It looked really terrible. The sound also wasn’t good. That was the beginning of the HiFiBerry DAC development.
But how bad is the onboard sound really? How bad is it compared to our DAC?

Lets have a look on the oscilloscope. We played a 1kHz sine wave on both the onboard output and the HiFiBerry DAC. Check it out:

onboardhifiberry-sin

It is not hard to see, that the onboard sound (left) ist not really a sine wave. Why is it that way? The onboard sound is not using a real DAC, but a simple pulse-width modulationĀ (PWM). While PWM is also used in good Class-D amplifiers (and works well there), the PWM circuit on the Raspberry Pi is trivial and not build for high fidelity sound.

Have a look at the distortions of both circuits:

thd_onboardthd_hifiberry

You clearly see, that there are much more noise and distortions on the onboard sound. The onboard-sound cannot provide high quality sound. However, we’ve seen circuits that were even worse than this one.

You want to use the Raspberry Pi for high-quality audio? Use an external sound card or our HiFiBerry DAC.

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