Sampling and Nyquist/Antialiasing filters

[Florian Anwander]

Hello Duane


>Is there anyone out there who has any basic guidelines on how many dB
>down "aliasing" frequencies have to be so they are not a problem?
I had the same problem with my Casio FZ-1. (36 kHz sampling rate and 14 kHz  
filter). After two heretical thoughts, I decided only to modify the input  
filter that way, that I can switch it off(!):

1.) the most sounds that I am sampling come from media that don't have the  
critical frequency-range (even on the best recorded CD there is no frequency  
over 22 kHz) so I don't have to care for.

2.) A sampler like a Prophet 2000 or the FZ-1 is a sampler and the sampler  
should sound like a sampler - not as perfect as the real world. If there is a  
little aliasing noise it doesn't disturb me, it is more like some glittering  
exciter effect.

Now I have a simple switch, witch bypasses the input-filter (and also one,  
that disables the signal routing for filtering at lower sampling rates, which  
is done in the FZ-1 with the Playback-DCFs). I insert a 24 dB Curtis filter  
(modified Doepfer A-122) in the input signalpath so that I can adjust the  
cutoff frequency to my desire. Easy thing, works very well ...


Gruss,
 Florian Anwander
-------------------------------------------------------------------------
Maus-Netz: Florian Anwander at M4
Internet:  fa at fa.camelot.de           http://www.camelot.de/~fa/
## CrossPoint v3.11 R ##