In all honesty I have seen measurements made by Amir (Schiit stuff I thought I remember) that had high distortion at a specific frequency and low again at a few Hz higher.
Frequencies that shift (or step in small steps) is not possible.
I don't think different filters do this in a different way.
Story about Schit is bad, and Amir finds many things the others would miss (or not publish). It is probably unrelated here.
Good point. I take your comment about shifting frequencies seriously. My interpretation was perhaps wrong,. You gave me a reason to think again and here is how it happens in nature:
Stage 1, hammer hit strings. Each string resonate with a tone, but it is not a natural frequency. There is a dominant pair of split frequences (a string is divided in two lenghts by a hammer and each part produce their own base frequencies and overtones). The value of these split frequencies is not controlled by the design, generaly there is a big mess at this stage, but nobody cares, as it lasts very short.
Stage 2, hammer bounces back. All strings begin oscilating freely, but frequency of each string is shifted from a natural (tuned) frequency proportionally to the amount of displacement applied by the hammer, it is not he same for each string. We hear an initial dissonance. It is perceived pleasant as it lasts short. If piano is tuned well, all strings form a coupled oscilator synchronising phase, also frequency shifts to a natural on a decay. If this set of strings is not tuned well, strings are unable to form coupled oscilator, we hear it as a detuned piano.
What I hear from Topping D30, it sounds like detuned piano. The initial dissonance is natural, but on the Topping tone is not cleaning up on decay. So you are right - DSP is not shifting frequency, but it registers stage 1 or the beginning of stage 2 and attempts (
wrongly) to clean this sound.
