ralphpnj wrote: 
> i just finished reading a really poorly written review of Auralic's
> Altair streaming DAC and in the review extensive coverage is given over
> to the various filters in the unit.
> So my question is:
> How are these "filters" different from a simple graphic equalizer or
> simple DSP or even, god forbid, tone controls?
> Note: the review is the March 2017 issue of Stereophile.

Hey Ralph,
Like Mnyb said, they're just referring to variations of the digital
oversampling antialiasing filter used in the DAC. Subtleties like the
presence of pre-ringing in the impulse response, passband, length of
filter can change the frequency response and determine how well aliasing
distortion is filtered out when the signal is upsampled.

My post this past week on the blog models what is seen with the MQA
filter for example:

SoX can do it but if you want a bit more control with the GUI interface,
iZotope RX does a great job with modelling the filter parameters. Have
fun experimenting and seeing if you can hear the difference.

Bottom line - unless you really fool around with the parameters and
strongly affect the frequency response (like with Ayre's filter and the
PonoPlayer), you're not going to hear much difference. If you play a
very loud track with clipping and square waveforms, then you might see
the ringing in the upsampled signal as well as intersample overload
distortions. With properly low-passed signal (as in all frequencies
<22.05kHz in a  16/44.1 file), then there's not going to be any ringing
in the output...

Archimago's Musings: (archimago.blogspot.com) A 'more objective'
audiophile blog.
Archimago's Profile: http://forums.slimdevices.com/member.php?userid=2207
View this thread: http://forums.slimdevices.com/showthread.php?t=106979

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