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Re: Fw: EDP Oversampling

I think Jesse is making a good point there. I had not understood he 
was asking about the HalfSpeed feature. Since the EDP does it by 
lowering the sample rate of the D/A it may sound less clean than with 
interpolation at full sample rate. And its not so wrong to call this 
process Oversampling.

I dont quite understand the thing about the older sampler though, 
since it needs to change the sample rate for each note you play 
simultaneously, so its not possible adapt the D/A convertor rate as 
the EDP does. Probably they use a simple interpolation in the old 

>The Echoplex and the old sampler pitch change by really changing the 
>sample rate on the D/A convertors. The newer sampler probably does 
>it digitally by interpolation techniques or other DSP pitch-shift 
>techniques, and maintains the same sample rate on the convertor. I 
>don't think oversampling or the anti-alias filtering would have 
>anything to do with the effect you are hearing.
>Oversampling isn't "smoothing out" the waveform. It is a 
>mathematical technique that spreads out the aliased frequency bands 
>so they aren't right next to each other. That makes it simpler to 
>filter out the aliased bands with a less-complex low-pass filter 
>with a gentler slope.
>At 02:39 AM 6/24/2004, Jesse Ray Lucas wrote:
>>I was just curious since comparing the sound of an older Akai S2000 
>>against the sound of a newer S5000 sampler.  Although both are 16-bit
>>samplers, the older model sounds "grittier" when you pitch samples down 
>>resample to a lower bandwidth.  The EDP sounds gritty, too, when you 
>>into halfspeed.
>>As I understood that article it was saying that during the D-A conversion
>>the oversampling process was the interpolation of in-between samples into
>>the signal to smooth the waveform out.
>>Just trying to figure out what makes that sound sound the way it does.  
>>you say it's the anti-aliasing filters that matter, then I believe you.
>>Thanks for the info.
>Kim Flint                     | Looper's Delight
>kflint@loopers-delight.com    | http://www.loopers-delight.com


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