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Basic technical question about digital source signals

Forgive if this is a stupid question, but the current thread about digital vs analog made me curious: if you look at an analog music signal you see (I think) summations of sine waves i.e. a signal waveform which is "smooth". I realize that there are many contributions to digital sound, but starting with the most basic, if you look at the output from a digital source e.g. on an oscilloscope, would it appear "smooth" i.e. has all the stairstepping that occurs when you convert digital to analog been smoothed out or would the signal appear jagged to some extent?

Thanks for your time.
berner99
millercarbon's avatar
millercarbon
12,531 posts
 
You're thinking that since digital samples values at different points that when played back its a string of discrete points instead of a continuous curve. That's not the way it works. Whether played back through an amp or viewed directly from a player to a scope it will always look nice and smooth.  

Just one in a very, very long list of reasons why specs, scopes and measurements are inferior to a good set of ears.
audio2design
1,351 posts
 
Berner99 on most DACs it would look smooth. There is a trend on most audiophile non oversampling DACs not to have an output filter. Depending on the bandwidth of their analog electronics in those DACs, it would either look much like a staircase or a staircase with rounded edges.
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cleeds
5,944 posts
 
berner99
... if you look at the output from a digital source e.g. on an oscilloscope, would it appear "smooth" i.e. has all the stairstepping that occurs when you convert digital to analog been smoothed out or would the signal appear jagged to some extent?
The "stairstepping" you refer to is really a misnomer, although it's widely believed. For proof, see this.
audio2design
1,351 posts
 
Cleeds,

In that video, he is showing the output of a DAC with an analog reconstruction filter. It is filtering out the stair-steps. Which goes back to my post, on most DACs, there would be no stair-step evident. On non oversampling DACs or any DAC without an analog filter, there would be evidence of stair-steps.
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