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RE: All FIR filters are fatally flawed.

Hey Tony, in case you forgot, the goal of the digital signal in question was to recreate two cycles of a 20KHz sine wave. Apparently, all your high-powered digital filters can’t do the job. How many more cycles does it take? Three or four…hundred….thousand….million? Regardless, what ever the number there will always be a discontinuity at the beginning and the end of the sample stream at which time the FIR filter will output undesired tones that are enharmonic to the frequency you are trying to reproduce. A NOS DAC can’t quite do the job either but it comes a lot closer.

Here is the very same two cycle, 20KHz signal processed by DAC N. It’s got about the right number of cycles and, most importantly, the right frequency.


Here is the same signal processed by DAC L, an unfiltered NOS DAC. It comes the closest to the truth provided your amp, speakers, and ears can filter out all the undesirable but audible frequency components of the stair steps and all the audible intermodulation distortion that may be produced by the inaudible frequency components of the steps.


Most audiophiles proudly claim to hear things that can’t be measured or observed with an oscilloscope. On the other hand, you claim the digital filter anomalies that can be observed with an oscilloscope are, nonetheless, inaudible. How convenient. You may not hear them but others do. In addition to the anomalies I documented, an FIR filter’s propensity to average adjacent samples sucks the life out of the music. Natural acoustic music has an unmistakable texture and that texture is reduced each time the music passes through a FIR filter. With the ubiquity FIR filters in all stages of music recording and production, most modern digital recordings sound more like the lifeless output of a digital synthesizer than real music created by humans singing and playing acoustic instruments.



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