Hello friends, I bought the Topping DX3 PRO LDAC. I have a question to ask. What do the various modes of the PCM filter set mean? What are the tone characteristics?
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The terms AKM uses are more confusing than helpful.
F-1 is the most traditional filter. Linear phase, no frequency response dip in the audible range.
F-2 is a linear phase filter, but allows some very modest high-frequency rolloff to reduce pre-ringing. Whether either of these is audible is a matter of debate; if neither is audible than it should be most similar to F-1.
F-3 is a minimum phase filter with no frequency response dip in the audible range. There is considerable phase shift at higher frequencies, which may affect imaging stability on speakers. There seems to be an anecdotal psychoacoustic effect where some people perceive minimum phase filters as slightly more rich or bassy, but there is little published research on this that I'm aware of.
F-4 is a minimum phase filter with a frequency response dip in the audible range. This is likely to reduce imaging solidity on speakers but might help some people if they feel music is too harsh.
F-5 is essentially no digital filter, and has a significant frequency response dip in the audible range. Of all the filters, this should be the most audible, but it's hard to argue that this is neutral sounding in a scientific sense.
F-6 is a goldilocks-style intermediate-phase filter, of the type Archimago writes about. It has only 8 degrees of phase shift at 18kHz, and also has no frequency response dip in the audible range. If you think you might be sensitive to pre-ringing (could be placebo) but don't want to sacrifice imaging on speakers, this is a good choice.