Using Direct (Non-Dma) Audio Output; Table 5-6 Sampling Rate And Frequency Relationship - Commodore Amiga A1000 Hardware Reference Manual

Table 5-6: Sampling Rate and Frequency Relationship
Maximum sampling rate
Minimum sampling rate
for 7 KHz output
Sampling rate too low
for 7 KHz output
In A2000s with 2 layer motherboards and later AS00 models there is a control bit that
allows the audio output to bypass the low pass filter. This control bit is the same output
bit of the 8520 CIA that controls the brightness of the red "power" LED. Bypassing the
filter allows for improved sound in some applications, but an external filter with an
appropriate cut-off frequency may be required.

USING DIRECT (NON-DMA) AUDIO OUTPUT

It is possible to create sound by writing audio data one word at a time to the audio output
addresses, instead of setting up a list of audio data in memory. This method of controlling
the output is more processor-intensive and is therefore not recommended.
To use direct audio output, do not enable the DMA for the audio channel you wish to use;
this changes the timing of the interrupts. The normal interrupt occurs after a data address
has been read; in direct audio output, the interrupt occurs after one data word has been
output.
Unlike in the DMA-controlled automatic data output, in direct audio output, if you do not
write a new set of data to the output addresses before two sampling intervals have
elapsed, the audio output will cease changing. The last value remains as an output of the
digital-to-analog converter.
The volume and period registers are set as usual.
Sampling Sampling
Period Rate (KHz)
124 29
256 14
320 11
- Audio Hardware 153 -
Maximum Output
Frequency (KHz)
7
7
4