Soekris no work with normalized values.
If the manufacturer's filters are simulated using MATLAB, each one has a different gain.
These are the maximum values of the current filters from the manufacturer.
dam1021,44100,8,1004,3999,6.4
6.4*0.121856689453125=0.779882
dam1021,44100,8,1005,3999,6.4
6.4*0.11328218648799343=0.72500599
dam1021,44100,8,1006,3999,6.4
6.4*0.068955347958631091=0.441314226
dam1021,44100,8,1007,3999,6.4
6.4*0.15039634256999757=0.96253659
dam1021,88200,4,1004,1999,3.2
3.2*0.221099853515625=0.707519531
dam1021,88200,4,1005,1999,3.2
3.2*0.20738172158894835=0.6636215090
dam1021,88200,4,1006,1999,3.2
3.2*0.14150686187062594=0.45282195
dam1021,88200,4,1007,1999,3.2
3.2*0.18662885483604397=0.59721233
dam1021,176400,2,1004,999,1.6
1.6*0.44219970703125=0.70751953
dam1021,176400,2,1005,999,1.6
1.6*0.40071213074587686=0.6411394
dam1021,176400,2,1006,999,1.6
1.6*0.25260014993372831=0.40416023
dam1021,176400,2,1007,999,1.6
1.6*0.30006640287583225=0.48010624
dam1021,352800,1,4,1,0.8
0.8*1.0=0.8
dam1021,352800,8,1008,239,8
8*0.0850830078125=0.6806640
dam1021,352800,8,1010,239,8
8*0.092368308679724967=0.738946469
I will work with filters normalized to 1 and with gains all set to 0.8, just like at 352800 Hz. To avoid any mistakes, I will ensure with measurements that there is no distortion at 0 dB. I will also measure the manufacturer's 2K and 4K filters to compare them with mine and ensure everything is done correctly.
- The DAC might have a gain of +10 dB, if I recall correctly.
- And now, another gain has been added to equalize something unknown.
If the manufacturer's filters are simulated using MATLAB, each one has a different gain.
These are the maximum values of the current filters from the manufacturer.
dam1021,44100,8,1004,3999,6.4
6.4*0.121856689453125=0.779882
dam1021,44100,8,1005,3999,6.4
6.4*0.11328218648799343=0.72500599
dam1021,44100,8,1006,3999,6.4
6.4*0.068955347958631091=0.441314226
dam1021,44100,8,1007,3999,6.4
6.4*0.15039634256999757=0.96253659
dam1021,88200,4,1004,1999,3.2
3.2*0.221099853515625=0.707519531
dam1021,88200,4,1005,1999,3.2
3.2*0.20738172158894835=0.6636215090
dam1021,88200,4,1006,1999,3.2
3.2*0.14150686187062594=0.45282195
dam1021,88200,4,1007,1999,3.2
3.2*0.18662885483604397=0.59721233
dam1021,176400,2,1004,999,1.6
1.6*0.44219970703125=0.70751953
dam1021,176400,2,1005,999,1.6
1.6*0.40071213074587686=0.6411394
dam1021,176400,2,1006,999,1.6
1.6*0.25260014993372831=0.40416023
dam1021,176400,2,1007,999,1.6
1.6*0.30006640287583225=0.48010624
dam1021,352800,1,4,1,0.8
0.8*1.0=0.8
dam1021,352800,8,1008,239,8
8*0.0850830078125=0.6806640
dam1021,352800,8,1010,239,8
8*0.092368308679724967=0.738946469
I will work with filters normalized to 1 and with gains all set to 0.8, just like at 352800 Hz. To avoid any mistakes, I will ensure with measurements that there is no distortion at 0 dB. I will also measure the manufacturer's 2K and 4K filters to compare them with mine and ensure everything is done correctly.
This is a set of 4k filters.
- 4k-Kaiser linear phase filter that improves on the manufacturer's version.Has less ringing in the passband, attenuates more in the stopband 170 dB, and has a higher cutoff frequency. It also has better bass response and a narrower impulse response. Best fase response.
- 4K-Nyquist. Linear pase filter improves the manufacturer´s versión. Has less ringing in the passband. Attenuates more in the stopband 170 dB. Has a higher cutoff frequency plaint to 22 kHz. It also has better bass response and a narrower impulse response. The Best fase response to 22 kHz. At the sampling point, it is exactly the value of the sample. The rest of the points are interpolated by 4k. This is the one with the least theoretical distortion.
- Quasi-NOS is a very short impulse with an impulse response almost as good as NOS but with a flatter frequency response. It's very similar to the manufacturer's F7 but shows less distortion.
- NOS. It makes the DAM behave exactly like a NOS DAC.
An example of a Matlab program on how I created them, in case anyone is interested in developing other filters. I had to develop graphs to experiment with values and compare the improvements with those from the manufacturer. I also created filters for 88, 96, 176, 192, and the F2 filter, but I’m not including them here as they are similar. I also read the manufacturer's coefficients to compare them with mine on the same graph, but I’m not including those here either