Mail till Audiolab i UK:
"Hello, Steve and thank you for the quick reply!
I was just wondering if there is
any way to change the anti-aliasing filter on the 6000N Play (e.g. with a firmware update)?
A look at the technical specifications of the 6000N Play at your webpage states:

- Audiolab_spec.jpg (10.14 KiB) Visad 378 gånger
The data for frequency response is definitely not there in real life, since you roll off from 10 kHz reaching some -1.5dB at 20 kHz. Better frequency response at 20kHz should require a much higher sampling frequency than 48 kHz or CDDA at 44.1 kHz. But “20 – 20 000 +/- 1.5 dB” would not look very good in an upscale digital product year 2021…
The THD and S/N is also quite questionable when you consider the aliasing products present with this type of slow rolloff filters, especially if you look just slightly above the 20 kHz bandwidth. The data you present is for a DAC with a different filter than what is implemented.
One review (7review.com) presented the following measured performance for this player:
Frequency response: 4 – 16 kHz (0.5 dB deviation)
Distortion: 0.15%
Dynamic range: 97dB
This quite mediocre technical performance is solely due to the anti-aliasing filter “Slow Rolloff” right? In my opinion, you are sacrificing actual technical performance for a (slightly possible but most likely only questionable) improvement in transient handling. If you have user-selectable digital filters the option to choose “Slow Rolloff”, “Optimal Transient” or the likes could definitely be there of course (I do not question that any particular listener could prefer these), but the sort of basic configuration for the player should be the technical better filters “Optimal Spectrum” or “Fast Rolloff”.
So a different digital filter would be highly appreciated.
Have a really happy new year!
/C"