The KA17 from Fiio has been a blast to use. It has tons of power, and the sound quality is great. I’m just looking for a bit of advice on its proper use, primarily in terms of these filters, which I don’t quite understand:
MINI: Minimum phase (default)
Conventional minimum phase filter. No front ringing, but significant rear ringing.
FAST A: Linear phase fast roll-off apodizing
Linear phase filters incorporating special window functions to optimize transient response. Theoretical.
FAST: Linear phase fast roll-off
Traditional linear phase filter. Symmetrical ringing. Audio DACs from 20 years ago commonly used this as the default filter.
FAST R: Linear phase fast roll-off low ripple
Conventional linear phase filters that reduce some ripple.
SLOW: Linear phase slow roll-off
Conventional linear phase filters with minimal filtering.
MINI F: Minimum phase fast roll-off
Approximates a “conventional minimum phase filter,” trading some ripple for a faster roll-off.
MINI S: Minimum phase slow roll-off
This filter is recommended if the song has a high sample rate, e.g., ≥176.4kHz.
MINI S D: Minimum phase slow roll-off low dispersion
This offers the most natural sound. Note: “Natural” does not necessarily mean “good,” especially with poor quality recordings.
Also, if you have any other tips or tricks I should know about the device, I’d be glad to hear them. Thank you in advance.
For linear vs. minimum-phase the explainer I’ve latched onto is this: Linear and minimum phase – Troll Audio
The author says there’s no conclusion to draw but their own graphs tell a different story: the minimum phase filter disperses the higher frequencies by different phase amounts and produces a signal that obviously does not look like the original whereas the linear one does. Meanwhile, the supposed “unnatural pre-ringing” of the linear filter is at such low amplitudes and high frequnecy (20-22 kHz) that it can’t be heard and was never a serious scientific argument against linear filters. So I would always pick a linear filter. (The “low dispersion” min-phase is interesting if they’ve managed it, but why bother when you can have NO-dispersion with the linear?)
Slow roll-off allows ultrasonic frequencies to pass, which could cause unknown problems depending on what the amp coming after the DAC knows how to do with them or not, but most likely might cause intermodulation distortion components at audible frequencies. Sometimes slow roll-off filters start the roll-off already in the audible band and literally veil the treble like an EQ (though I don’t think FiiO are this bad at it after all this time). Better use a fast roll-off.
I would just pick the supposedly “20 years ago” linear fast, that does what a DAC’s reconstruction filter for music consumption should do. Its only bad effect is delaying the output vs. the input, which becomes a problem only if you plug a lot of effects processors into eachother because the delay adds up, but that is the stuff of complicated production/live setups. Engineers dealing with those setups are the only people who really need to worry about min-phase options and what differences there are between them.
Huh, according to GoldenSound the apodizing version of the linear filter can fix some problems introduced by the possibly bad ADC used when making the original recording. This is the first thing I’ve heard/read that makes the apodizing option attractive to me (when the term is not misused to designate just a minimum-phase filter). I might just set my KA17 to apodizing if I stick to my plan of getting one in this November in discount season.
LE:
Welp, according to the ESS datasheet for the 9069 the apodizing filter starts to roll off in the audio band around 18k and is already 5 dB down or worse by 20k. That’s a big nope for me dawg. I’d have to know for sure I’m listening to recordings that have the “ADC ringing” problem in them to use such a filter.