Filter Selection: does it actually work on Tone2 Pro?

I decided to do some frequency response measurements of my shiny new Tone2 Pro this afternoon to see how it compares to my old Tone1. Before I got into comparisons, I wanted to see how different filters affect the response at 48 kHz. On my other DACs with selectable filters, there’s a subtle but significant impact, especially at lower sampling frequencies.

Testing the Tone2 Pro with an input sampling rate of 48 kHz and cycling through all seven filters, I measured EXACTLY the same response for each. That’s a bit troubling. I’m now wondering if the filter selection via the big dial actually works.

I have an S.M.S.L. Sanskrit 10th V2 that also offers different filters. This plot shows how the response differs when different filters are selected:

I expected to see a similar level of differences between filters on the Tone2 Pro

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Note: Not related to my support question about filters, but may be interesting to some…

Since most of the music we listen to is still encoded at sampling rate of 44.1 kHz, here’s a comparison between the response of the Tone1 and the Tone2 Pro at that rate. I’ve compensated for the 1.14 dB difference in output, as the Tone1 has a bit more volume.

As you can see, the Tone2 pro definitely looks smoother. As I said before, I’m not sure that this difference is audible…except possibly to bats.


Another example…different filter settings on my iFi Audio micro iDSD Signature: