Use of fast/slow filters in Reference CD9
 

The difference between the "fast" and "slow" filters in the CD9 is pretty pronounced to my ears when playing conventional CD's. However, when playing HD files (typically 176.4 kHz and 24 bit) I don't hear the same degree of differences. I'm wondering what other CD9 owners hear with HD music playback.

With my limited understanding of the subject, your observation makes perfect sense to me.

At the CD sample rate of 44.1 kHz, the fast filter must be really aggressive to allow a frequency response up to (around) 20 kHz, while still suppressing digital artifacts above the Nyquist frequency at 22.05 kHz. This gives a very sharp roll off, in contrast to the slow filter which rolls off more slowly.

At 176.4 kHz, the fast filter doesn't need to be at all as aggressive, because a flat frequency response all the way up to 80 kHz isn't critical. At higher sample rates, the fast and slow filters can have quite similar responses.

I've actually only had my CD9 for about a week, so I haven't played around with the filter settings yet. I want to get accustomed to the CD9 at default settings first.

Thanks for sharing your observations!

Lars-Ola - My thinking on this is along the same lines as yours. However, sometimes theory and practice are two different things. That's why I ask the question. :D

To me it sounds more dynamic on slow filter

have the same thought as sonicmatter, after some trial and error, I settle with slow filter with 176.4 sample rate.

Use of fast/slow filters in Reference CD9
 

I use the fast and slow filters by intuition. If I’m not connecting emotionally with a recording, then I swap filters. Sometimes that does the trick. Generally, though, the fast setting tends to work best for lesser streaming sources in my system and I tend to prefer slow setting on disc playback.

I owned the Ref CD9 for about one year. I found that it sounded the most natural with the Slow Filter and Native Sampling. After experimenting extensively and making this determination, I never changed the settings after that and I was quite satisfied with the sound quality.

Ken