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#381 | |
diyAudio Member
Join Date: Mar 2005
Location: Blaricum
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Quote:
Two filters in series, the second one working at twice the speed, but both having the same set of coefficients that Hayk used now. When leaving a section signal rings at Fs/2, true ? So the first section will ring at 22.05khz and the second at 44.1Khz. How could this result in a combined ringing only at 22.05Khz ? Hans |
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#382 |
diyAudio Member
Join Date: Mar 2003
Location: Haarlem, the Netherlands
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Because there is nothing exciting the second filter's ringing.
At the output of the first filter, you have a signal band from 0 to 22.05 kHz, from 66.15 kHz to 110.25 kHz and copies every 88.2 kHz. How is that going to excite ringing at or just above 44.1 kHz? |
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#383 |
diyAudio Member
Join Date: Dec 2015
Location: south east asia
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Giving extra gain of 0.45% to midpoints, the 24khz image vanishes.
dissapear.JPG I am now looking to interpolate the sinc looking only the 30 succeeding samples to avoid pre ringing. |
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#384 | |
diyAudio Member
Join Date: Mar 2005
Location: Blaricum
|
Quote:
But when using only one and placing a second identical segment working at 2Fs behind the first, there are only two filters in action. You might be true, but I have a problem understanding how these two versions can produce the same result with only 2/3 of the amount of multiplications. Hans P.s. But at the end the result is in both cases that there are three interpolated points. So your thesis can’t be that far off. Funny problem. Last edited by Hans Polak; Today at 07:11 AM. |
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#385 | |
diyAudio Member
Join Date: Mar 2005
Location: Blaricum
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Quote:
Hans |
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#386 | |
diyAudio Member
Join Date: Mar 2003
Location: Haarlem, the Netherlands
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Quote:
Interpolation by large factors is usually done with a chain of interpolating filters, the filters getting simpler and simpler as you go further down the chain. The last couple of stages are often CIC filters, which just have adders, subtractors and registers and no multipliers at all. |
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#387 |
diyAudio Member
Join Date: Mar 2005
Location: Blaricum
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Marcel,
Yes, with two filters in series, the second filter has to produce two interpolations versus only one for the first filter. So in effect three convolutions have to be calculated in series between two original samples, exactly the same as with three parallel filters. So the amount of multiplications is the same in both cases, par. or serie. ![]() Hans Nice trick to make filters simpler down the chain. Last edited by Hans Polak; Today at 08:34 AM. |
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#388 |
diyAudio Member
Join Date: Dec 2015
Location: south east asia
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I found an alternative sinc interpolation that doesn't have ringings.
modif sinc.JPG The formula is too complicated for me to understand. modified sinc.JPG Interpolation: Find good approximation from given samples I will try to decipher by trial and error, or may be my son (PhD), too busy, can do it. |
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#389 |
diyAudio Member
Join Date: Mar 2005
Location: Blaricum
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Interesting, never seen this before in a DAC.
Let your son pay attention, I'll do the same. Anxious to see what the FFT of this impulse response will show. Hans |
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