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16x Digital interpolation filter - drive PCM56, PCM58, AD1865 and so on up to 768 kHz
16x Digital interpolation filter - drive PCM56, PCM58, AD1865 and so on up to 768 kHz
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Old 16th April 2019, 10:03 AM   #81
merlin el mago is offline merlin el mago  Europe
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1st post: "The price for a fully assembled and ready to use board will be 150 EUR."
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Old 16th April 2019, 11:03 AM   #82
3lite is offline 3lite  Poland
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I cannot promise it will work though. It purely depends on the available clocks. However, as mentioned within first post following lower frequency clocks (usually BCLK which can be connected to MCLK input of my digital filter) can work as a master clock (MCLK) signal:

6.144 MHz
5.6448 MHz
4.608 MHz *
4.2336 MHz *
3.072 MHz
2.8224 MHz
1.536 MHz
1.4112 MHz
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Old 16th April 2019, 11:52 AM   #83
dreamth is online now dreamth  Romania
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thank you!
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Old 19th April 2019, 06:50 AM   #84
Hans Polak is offline Hans Polak  Netherlands
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Quote:
Originally Posted by 3lite View Post
I cannot promise it will work though. It purely depends on the available clocks. However, as mentioned within first post following lower frequency clocks (usually BCLK which can be connected to MCLK input of my digital filter) can work as a master clock (MCLK) signal:

6.144 MHz
5.6448 MHz
4.608 MHz *
4.2336 MHz *
3.072 MHz
2.8224 MHz
1.536 MHz
1.4112 MHz
Extremely impressive what you have achieved.
What could possibly be the reason that a long FIR filter sounds better than a shorter version as usually found in Dacís
Looking at specís from Dacís, they all have very low pass band ripple, very high stop band suppression, linear phase and low THD.
But all (digital) filters suffer from time smearing, the sharper the transition from pass to stop, the more ďsmearingĒ. No filter can escape these physical laws.
So there must be something else why longer filters are sounding better, any idea why ?

Hans
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Old 19th April 2019, 07:55 AM   #85
chris719 is online now chris719  United States
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16x Digital interpolation filter - drive PCM56, PCM58, AD1865 and so on up to 768 kHz
Quote:
Originally Posted by Hans Polak View Post
Extremely impressive what you have achieved.
What could possibly be the reason that a long FIR filter sounds better than a shorter version as usually found in Dac’s
Looking at spec’s from Dac’s, they all have very low pass band ripple, very high stop band suppression, linear phase and low THD.
But all (digital) filters suffer from time smearing, the sharper the transition from pass to stop, the more “smearing”. No filter can escape these physical laws.
So there must be something else why longer filters are sounding better, any idea why ?

Hans
Psychology?

A typical synchronous interpolation filter like this, being LTI, doesn't create harmonic distortion. You don't see that specified on filters like this.

This "time smearing" isn't an artifact, so I really dislike using that term for it. An ideal reconstruction filter will have this "time smearing", but it will reconstruct the original waveform perfectly. It's not actually time smearing, because we don't listen to impulses.

It's often possible to improve on the built-in filters because they typically allow for some aliasing in the transition band in order to meet the marketing requirement of a 20 kHz passband with the number of taps they are afforded.

This is a really nice effort. I'd definitely get one if I were using one of the DACs it's designed to interface with.

Last edited by chris719; 19th April 2019 at 07:59 AM.
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Old 19th April 2019, 09:50 AM   #86
Hans Polak is offline Hans Polak  Netherlands
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Quote:
Originally Posted by chris719 View Post
Psychology?

A typical synchronous interpolation filter like this, being LTI, doesn't create harmonic distortion. You don't see that specified on filters like this.

This "time smearing" isn't an artifact, so I really dislike using that term for it. An ideal reconstruction filter will have this "time smearing", but it will reconstruct the original waveform perfectly. It's not actually time smearing, because we don't listen to impulses.

It's often possible to improve on the built-in filters because they typically allow for some aliasing in the transition band in order to meet the marketing requirement of a 20 kHz passband with the number of taps they are afforded.

This is a really nice effort. I'd definitely get one if I were using one of the DACs it's designed to interface with.
I donít get this aliasing, I see no technical reason for that, but I agree that the signal might become corrupted by this filter process in some way and that longer filters may produce lesser corruption anomalies.

Hans
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Old 19th April 2019, 10:01 AM   #87
chris719 is online now chris719  United States
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16x Digital interpolation filter - drive PCM56, PCM58, AD1865 and so on up to 768 kHz
Quote:
Originally Posted by Hans Polak View Post
I don’t get this aliasing, I see no technical reason for that, but I agree that the signal might become corrupted by this filter process in some way and that longer filters may produce lesser corruption anomalies.

Hans
Uh... The filter must be in the stopband by the Nyquist frequency in order to avoid any aliasing.

Most DACs have built in filters which have specs like Passband: 0.454*Fs, Stopband: 0.546*Fs (taken from PCM1792A datasheet).

This means the filter is not fully into the stopband until 24.078 kHz when Fs = 44.1 kHz. This is > Fs/2. The passband is conveniently 20.02 kHz. This is chosen so the marketing department doesn't have to explain why their DAC isn't flat to 20 kHz. The filter would have to be longer in order to narrow the width of the transition band.


There's no need to talk about ambiguous corruption, because it's all quantifiable. Fortunately, 3lite has produced a nice set of filters here.

Last edited by chris719; 19th April 2019 at 10:03 AM.
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Old 19th April 2019, 10:40 AM   #88
Luke is offline Luke  New Zealand
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16x Digital interpolation filter - drive PCM56, PCM58, AD1865 and so on up to 768 kHz Send a message via AIM to Luke
Hi 3Lite, my intention is to run Ian's I2S to PCM after this as I am building balanced dac. Do you foresee any issues with this configuration?
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Old 19th April 2019, 12:03 PM   #89
Hans Polak is offline Hans Polak  Netherlands
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Quote:
Originally Posted by chris719 View Post
Uh... The filter must be in the stopband by the Nyquist frequency in order to avoid any aliasing.
Nyquist can stay at home, we are discussing filtering of an upsampled signal. No aliasing or backfolding takes place.
And in case the digital filter leaves some residue from 22kHz to 24kHz, this will simply appear in the analogue signal after d/a conversion still residing at 22kHz to 24kHz.
I don't think anyone will notice that.


Hans
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Old 19th April 2019, 03:48 PM   #90
chris719 is online now chris719  United States
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16x Digital interpolation filter - drive PCM56, PCM58, AD1865 and so on up to 768 kHz
Nevermind

Last edited by chris719; 19th April 2019 at 03:55 PM.
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