Once again I am visiting the most confusing aspect of high end audio: PCM filters.
I have a Mark Levinson 5101 CD/SACD player, and recently performed a firmware update and system reset. What I noticed is that they chose as the default PCM filter Fast Minimum Phase.
Up to now I kindof settled into Slow Linear Phase.
When I say settled I mean it wore me out and beat me down.
Now that I am a proud owner of a BHK preamp (thanks for the help Paul), I’m not sure the benefits of either.
Could someone help me understand the difference between these two filters?
(from the RME ADI2 manual but the same shiz applies)
High level view:
the yellow line is a slow filter, Orange is very fast.
The speed is just about how rapidly the filter cuts off above a certain frequency (in this case, the cutoff frequency is around 20 kHz).
The minimum phase filter will cause phase shift towards the top of the frequency range, the linear phase filter will not (but has other drawbacks - google “pre-ringing”).
Ultimately, use whichever sounds best to your ears, which will be different dependent on person, gear, room, even the particular type of music playing etc.
I have noticed that the FMP filter sounds better on some recordings while dull on others.
Likewise, I have noticed that the SLP filter sounds better on other recordings while bright on others.
I find it interesting that all the articles I read suggest that these filters are very subtle and most likely cannot be heard in audio since the effect frequencies that are too high for the human ear. Yet with my setup they do have a distinctive effect on the sound. Not sure if my speakers are extremely revealing or how to explain it.
I do hear differences in filters, used to on my PWD and do on my Oppo UDP-205. Not very subtle, though subtle. On the Oppo the one that I like the most for sound over all the sources is Corrected Mini Phase Fast, which may only be selectable on this machine, haven’t seen it elsewhere…
According to Mark Levinson tech support they state the following about their default PCM filter?
This is the default PCM filter because “Fast Minimum Phase” filters have steeper roll-off at high frequencies and thus do a better job of attenuating unwanted high frequency “aliased” signals.
Well, yes, they do, they also cause phase shift towards the top end (the minimum phase bit).
You could have a fast linear phase that would do the same.
It might sound a bit different though (no phase shift, and a different design/implementation of a filter).
When it comes down to it there is no “correct” filter, and the differences and impacts of the different types affect music differently dependent on many variables.
Try 'em all and see what you like, and if you can’t tell much difference then it doesn’t make much difference
