Joe Bloggs
Sponsor: HiByMember of the Trade: EFO Technologies Co, YanYin TechnologyHis Porta Corda walked the Green Mile
The GTO filter reads to be a 32-tap (very short) minimum phase antialiasing filter. It appears to be advertised as a happy medium between non-oversampling and... almost any other antialiasing filter, because they are all longer and have longer "ringing" response to a "Kronecker delta" input. Here I would just like to note that the objective of an antialiasing filter is to filter out the normal ultrasonic artifacts of digital-analog conversion, and the longer the filter, the better this filtering can usually be done and the ringing tail would be inaudible, unless you can hear above 21kHz for 44.1kHz input, 44kHz for 96kHz input, etc... because that's what the ringing consists of, a narrow band of ultrasonic frequencies in the transition band of the AA filter. The longer and more precise the AA filter, the narrower this band is, and hence the longer the ringing, but in all cases it should be ultrasonic. Conversely the ultrasonic artifacts that these filters aim to take out (but not so much in the case of the GTO filter) are ALSO ultrasonic and so also probably inaudible, BUT can become audible through intermodulation distortion, if the amplification / speaker / headphone electronics / physics are non-linear (i.e. with significant THD) at those frequencies, which they are more likely to be than for audible frequencies, because people don't usually ask even HiFi stuff to have low distortion up into the megahertz.
Disclaimer: brief former iFi employee (part time, social media section)
Disclaimer: brief former iFi employee (part time, social media section)
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