NON-OS DAC
Gentleman,
This discussion is way over my head and leading to nowhere...
If I have a look at the 3150Hz sinewave at the scope at the output of a NON-OS DAC with no analog filtering applied I see a nice staircase on top of the sinewave. This <B>might</B> be a exact representation of the <B><I>digitized </B></I>wave form of the original sine wave. But it is <B>not</B> a exact representation of the <B>original</B> sine wave. When I connect a analog sine wave generator to my scope I see a smooth sinewave no steps. To get a smooth sinewave I had to lowpass filter the signal. By experimenting I found that a 10kHz crossover third order Bessel can do the job.
Now for the 8x oversampling DAC. Again no analog lowpass filtering applied. Hey now I see a sinewave with much smaller steps in the staircase on top of the sine wave! Again lowpass filtering has to be applied but now at a much higher frequency and having no attenuation in the audioband (20-20kHz)
Concluding the whole digital filtering concept looks like brilliant but I did not like it sonically...I don't have a plausible explanation for this result.
Footnote
As a squarewave; and the staircase is composed of small squarewaves; can be thought of a sine wave combined with a lot of higher harmonics of it, this tells me that a 8x oversampling DAC has these harmonics at a much higher frequency.
Gentleman,
This discussion is way over my head and leading to nowhere...
If I have a look at the 3150Hz sinewave at the scope at the output of a NON-OS DAC with no analog filtering applied I see a nice staircase on top of the sinewave. This <B>might</B> be a exact representation of the <B><I>digitized </B></I>wave form of the original sine wave. But it is <B>not</B> a exact representation of the <B>original</B> sine wave. When I connect a analog sine wave generator to my scope I see a smooth sinewave no steps. To get a smooth sinewave I had to lowpass filter the signal. By experimenting I found that a 10kHz crossover third order Bessel can do the job.
Now for the 8x oversampling DAC. Again no analog lowpass filtering applied. Hey now I see a sinewave with much smaller steps in the staircase on top of the sine wave! Again lowpass filtering has to be applied but now at a much higher frequency and having no attenuation in the audioband (20-20kHz)
Concluding the whole digital filtering concept looks like brilliant but I did not like it sonically...I don't have a plausible explanation for this result.
Footnote
As a squarewave; and the staircase is composed of small squarewaves; can be thought of a sine wave combined with a lot of higher harmonics of it, this tells me that a 8x oversampling DAC has these harmonics at a much higher frequency.
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