Music & Harmonics

[Bksabath]

As you may guessed I am pretty dumb (or chose to be😀 )
I mean the dumb part because I am quite pretty in a manly sort of way, meat and 2 veg like.😕

Lets start again

As you may guessed I am handsomely dumb (or chose to be😀 )

I don't need precise answers the math terrorize me and tend to cover whit spots and zits each time I see the square root of -1

So my dilemma is being a filter the filter filters out bits of things
The question in pretty dense precise terms is :


What does the anti aliasing filter filters out in particular (if this is what is called) in the recording/ mastering of standard CD?

 

[DF96]

The anti-aliasing filter removes all signals near, at and above half the sampling frequency. For CD that means from 22kHz (or maybe around 20kHz). Very few people can hear anything around there, and not many loudspeakers can produce sound around there. Hence it is removing stuff which few can hear anyway.

 

[Bksabath]

Tank you

I am not going to dispute that Fezzle is wrong au contrair
I let you do that

So 5 th harmonic is removed for any fundamental at around and over 4.4 kHz?

 

[Fezzle]

The anti-aliasing filter removes all signals near, at and above half the sampling frequency. For CD that means from 22kHz (or maybe around 20kHz). Very few people can hear anything around there, and not many loudspeakers can produce sound around there. Hence it is removing stuff which few can hear anyway.

Indeed however there is a but! The surrounding analog design to this filter and the filter itself is critical to the performance here, just because we cannot hear stuff up there does not mean it cannot cause problems that we can hear.. What the filter (no matter how good) does not do is reject intermod distortion products caused by sonics at around and above and beyond that region, that have folded back into the audio band.. Its the same deal with quality transformers and why theyre good at this kind of job for EMI/RF rejection. In fact a passive circuit can trump a DSP nyquist filter in this regard, and maintain better CMRR and time domain performance.

 

[DF96]

Of course the filter can't remove stuff within its passband. It needs to be linear, so it doesn't generate new stuff - but this is a requirement for all audio systems.

Transformers are about the least ideal passive components used in electronics, which is why they are only used when their strengths are needed (e.g. CMRR), their weaknesses can be tolerated (e.g. limited bandwidth) and there is no reasonable alternative.