Paradox.Delta
New Head-Fier
Hey guys, I was researching why DACs use oversampling to help with filters and came across a point that I just can’t explain. Hope you can help me out.
What I understood so far:
When audio is made, you record a sound that probably has frequencies above 22kHz and if you sample these in 44,1kHz they are recognized as another audible frequency since there are multiple waves between two samples. This pops up as aliasing in your recording. Or you synthesize a sound with some combined sine-waves that create frequencies like that. So the producer masters his recording, cleans everything above 22kHz in the process and puts these cleaned recordings as discrete 16bit values in 44,1kHz timesteps on a CD.
Now when you play the CD, you want to aproximate the original voltage curve from these 16bit values. So you alter your output voltage according to the 16bit value, wait for the time interval and apply the next voltage. This roughly results in a staircase function for the voltage output. But why is the DAC supposed to add another brickwall filter? The source material on the CD should already be void of anything higher than 22kHz. How is the aliasing reintroduced? Is it because of the staircase form of the voltage? Quantization noise? Or is it another strange mirroring effect that I can’t wrap my head around?
Thank you very much in advance.
What I understood so far:
When audio is made, you record a sound that probably has frequencies above 22kHz and if you sample these in 44,1kHz they are recognized as another audible frequency since there are multiple waves between two samples. This pops up as aliasing in your recording. Or you synthesize a sound with some combined sine-waves that create frequencies like that. So the producer masters his recording, cleans everything above 22kHz in the process and puts these cleaned recordings as discrete 16bit values in 44,1kHz timesteps on a CD.
Now when you play the CD, you want to aproximate the original voltage curve from these 16bit values. So you alter your output voltage according to the 16bit value, wait for the time interval and apply the next voltage. This roughly results in a staircase function for the voltage output. But why is the DAC supposed to add another brickwall filter? The source material on the CD should already be void of anything higher than 22kHz. How is the aliasing reintroduced? Is it because of the staircase form of the voltage? Quantization noise? Or is it another strange mirroring effect that I can’t wrap my head around?
Thank you very much in advance.