[sdiy] TX81Z, YMxx chips, and aliasing

[John Ames]

Suffice to say, whether or not there's a practical workaround, in
practice Yamaha FM aliases so much that I've heard DX7 patches that
use it as a sound source.

On 9/5/18, Declare Update <declareupdate at gmail.com> wrote:
> Ah! very good point. thanks.
>
> Chris
>
>> On Sep 5, 2018, at 4:14 PM, Michael Zacherl <sdiy-mz01 at blauwurf.info>
>> wrote:
>>
>>
>>> On 3 Sep 2018, at 09:43, Declare Update <declareupdate at gmail.com> wrote:
>>> Do the yamaha FM chips, such as the YM2414 in the TX81Z, do anything
>>> toward anti-aliasing? more specifically, does anyone know if they use
>>> band limited tables for their extra wave forms besides sine, and is there
>>> any attempt to band limit the signal after FM is applied?
>>
>> On the bottomline bandlimiting the source wave forms is moot, since it’s
>> the FM’s sidebands which cause the aliasing (and are responsible for the
>> rich spectrum).
>> So even when using just sine waves you may get side bands which get above
>> Nyquist and/or below zero.
>> m.
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