Re: [hatari-devel] 7an's Hi-Hats

[David Savinkoff <dsavnkff@xxxxxxxxx>]

----- Nicolas Pomarède wrote:
> Le 30/06/2017 à 16:57, David Savinkoff a écrit :
> 
> > We may need to know the register settings and code used
> > for the hi-hats to investigate the sound. Maybe the hi-hats
> > are very particular (maybe use tone and noise) and hard
> > to emulate.
> 
> Yes, I already contacted 7an some days ago to ask if he could send some 
> sample music files with very "simple" instruments that don't suond right 
> at the moment (not a whole music with all 3 voices playing at the same 
> time).
> 
> This way we can record on real STF and compare those paricular sounds 
> (and their corresponding register settings) with the emulation.
> 
> Nicolas
> 

I think that the noise is aliasing with the sample frequency. Note
that aliasing comes from (1) the abrupt changes of the rectangular
waveform, (2) modulating the noise waveform pulse width, and
(3) also from generating samples for a waveform which is of a
frequency beyond the nyquist limit.

Thus we are getting more noise than we bargained for (maybe
even 60% alias noise with 40% desired noise). The filter method
to use, is to lower the level of the noise (similar to the efficient
method we use for transient DC offsets).