Which DAC Filter - Fast or Slow?

I know. “The one that sounds the best”.

But I’m wondering if there is a general leaning on this topic, or if the results are just totally mixed.

I’ve read that using a fast filter will result in a higher top-end frequency response. Which is very obviously the case when using a fast filter on my Gryphon Diablo300 integrated amplifier’s DAC module. In systems prone to being bright or harsh, this could be a bad thing. That’s not an issue in my system - higher highs is a good thing.

I’ve also read that the trade off to fast filters is that the frequency response is less stable than slow filters - that the response will oscillate. I also think I can hear this? But I’m not sure.

Finally, people seem to say that the downsides of fast filters don’t matter because the flaws that are introduced are too minute to be audible. I’m not actually sure I believe that. But, in general I think I do prefer the fast filter overall. Crisper, quicker transients, more finesse, and, well, faster. I do get that it is system dependent, as I’ve found the filter does impact the sound differently when different servers are used.

What do others use, fast or slow, if they have the choice with their DACs?


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I use both on my dac because I can do it with a remote. It is easy to fit either slow or fast to any record as they all vary in tonality. Fast is best for any darker sounding record, slow best for bright records, simple as that. I will say that fast in my house of stereo results in a fuller, wider sound, but that can at times be so huge that it takes away from the locality of instruments and results to a less intimate sound setting. They both have their plus and minuses, which is why I would never have a dac without a remote.


I have an smsl su9 pro and I turn off all filters for a neutral filter is high fi in definition

John Atkinson typically does nice thorough measurements of reconstruction filter responses in Stereophile’s DAC reviews. Here is a link to a high end Gryphon player measurements, showing the differences in the various filters. 


In my understanding a “fast” filter has a very steep low pass transition. Sometimes called a “brick wall” filter with virtually zero signal above 22.05 kHz (for 44.1 kHz sample rate).  This allows less roll-off below 20 kHz. 

Impulse response is one of the characteristics of different filters. Typically a “fast” filter will have significant pre-ringing which might sound unnatural. 

On the good side a “fast” filter generally reduces the chances of aliased artifacts being artificially created above the Nyquist Frequency (22.05 kHz for redbook). 

In my experience, some DACs have obvious sonic differences between their filter choices. Some not so much.