John Atkinson: Yes, MQA IS Elegant...

[Shadders]

3 minutes ago, Fokus said:

 

That is abundantly clear.

 

Once more ... you claim that you investigate the ringing in isolation, and you claim that the ringing envelope emcompasses frequencies down in the passband. In other words, you claim that the ringing itself has audible content all over the passband. This means that the filter creates new spectral content, well below the filter's transition frequency.

 

Now tell us the main properties of a linear operator.

 

Hi,

Are you are referring to the filter being a linear system that adheres to the superposition theorem ? That is :

 

Assume T is the operator :

 

T[a1.x1(n) + a2.x2(n)]   = a1.T[x1(n)]    +   a2.T[x2(n)]

 

Or are you stating that the response of the filter is linear ?

 

Regards,

Shadders.

[Fokus]

A linear operator cannot create new spectral content.

[Shadders]

5 minutes ago, Fokus said:

A linear operator cannot create new spectral content.

Hi,

Ok. When you state linear operator, do you mean a linear system ?

Regards,

Shadders.

[Fokus]

A linear, time invariant system, ... like a filter.

[Shadders]

1 minute ago, Fokus said:

A linear, time invariant system, ... like a filter.

Hi,

OK - then this applies :

A linear system that adheres to the superposition theorem. That is :

 

Assume T is the operator :

 

T[a1.x1(n) + a2.x2(n)]   = a1.T[x1(n)]    +   a2.T[x2(n)]

 

The other criteria i did not mention is that the system has to be relaxed. Then given this, i would agree, that the output of the system can only be linearly related to the input.

 

If you then examine my examples of the ramp, or the sine with discontinuity which is relaxed to a tangent, where both exhibit "ringing", then there is something else occurring.

 

Maybe it is the term "ringing" that is the problem, where this is always attributed to the impulse response, or out of band energy applied to the filter.

 

In any case, the distortion occurs with transients.

 

Separate issue, the envelope of ringing does have energy within the passband.

 

Regards,

Shadders.

[Fokus]

I was not asking you what a linear system is.

 

I asked the question for you to ponder what this means in the face of your claim

 

" Separate issue, the envelope of ringing does have energy within the passband. "

 

[Shadders]

17 minutes ago, Fokus said:

I was not asking you what a linear system is.

 

I asked the question for you to ponder what this means in the face of your claim

 

" Separate issue, the envelope of ringing does have energy within the passband. "

 

Hi,

I am in agreement with you - that ringing if caused by an impulse, is purely the filter response, and when transformed to the frequency domain will be the frequency response of the filter. As such, the ringing does indeed have frequencies from 0Hz to the transition band - based on its waveform which includes its envelope.

 

Regards,

Shadders.

[mansr]

20 minutes ago, Shadders said:

I am in agreement with you - that ringing if caused by an impulse, is purely the filter response, and when transformed to the frequency domain will be the frequency response of the filter. As such, the ringing does indeed have frequencies from 0Hz to the transition band - based on its waveform which includes its envelope.

That's just a very roundabout way of stating that if the input contains all frequencies, as is the case with an impulse, the output will also contain all frequencies up to the filter cut-off. If it didn't, you'd have a high-pass filter.

[Shadders]

1 minute ago, mansr said:

That's just a very roundabout way of stating that if the input contains all frequencies, as is the case with an impulse, the output will also contain all frequencies up to the filter cut-off. If it didn't, you'd have a high-pass filter.

Hi,

Maybe, just needed to state where there was an agreement.

Regards,

Shadders.

[Fokus]

Moreover, mentioning the envelope in this story is quite irrelevant.

[mav52]

On 8/21/2018 at 3:42 PM, Ralf11 said:

the burden of poof is on MQA

 

So very true and right now the only people trying to prove it for MQA are some of the maganize editors that drink the cool aid and are too far into their fairly tales to turn back.

[Shadders]

10 minutes ago, Fokus said:

Moreover, mentioning the envelope in this story is quite irrelevant.

Hi,

It is not irrelevant. If the envelope was different, then the frequency spectrum would be different.

 

The envelope is essentially critical to the signal being analysed.

 

Regards,

Shadders.

[Fokus]

11 minutes ago, Shadders said:

It is not irrelevant. If the envelope was different, then the frequency spectrum would be different.

 

If the envelope were different then the filters would be different. And in discussing filters we talk about transition frequency, transition band(width), steepness/order, ... There is no need to single out the envelope of the (impulse) response.

 

[plissken]

1 minute ago, Fokus said:

 

If the envelope were different then the filters would be different. And in discussing filters we talk about transition frequency, transition band(width), steepness/order, ... There is no need to single out the envelope of the (impulse) response.

 

 

Good luck with Shadders there. Unfortunately I think you are wasting your breath. 

[Shadders]

27 minutes ago, Fokus said:

 

If the envelope were different then the filters would be different. And in discussing filters we talk about transition frequency, transition band(width), steepness/order, ... There is no need to single out the envelope of the (impulse) response.

 

Hi,

You are confusing what you know about the filter with the analysis of a waveform.

 

If you were presented with the impulse response without prior knowledge of the system, you would implement the frequency transform, and see the result.

 

Just because you "know" about the system does NOT stop the envelope being critical to the frequency spectrum of the signal.

 

Anyway, it is the examples given, such as the ramp and the sine wave with discontinuity at the 0.5volts signal value relaxed to a tangent, which shows you that there is a variation in the output of the filter which is not ringing (where ringing always been attributed to energy outside the passband).

 

Regards,

Shadders.

[Fokus]

Deep sigh ...

[mansr]

50 minutes ago, Shadders said:

You are confusing what you know about the filter with the analysis of a waveform.

 

If you were presented with the impulse response without prior knowledge of the system, you would implement the frequency transform, and see the result. 

  

Just because you "know" about the system does NOT stop the envelope being critical to the frequency spectrum of the signal.

You're looking at this backwards. The envelope is a result of the spectrum.

[Shadders]

1 minute ago, mansr said:

You're looking at this backwards. The envelope is a result of the spectrum.

Hi,

No, the envelope is part of the response of the system - where the response just happens to be the filter coefficients.

 

Assume you were given the signal as a sample from someone and told to investigate, and you did not know that it was the impulse response of a filter.

 

Prior knowledge skews peoples approach.

 

Regards,

Shadders.

[Shadders]

5 minutes ago, Fokus said:

Deep sigh ...

Hi,

Which part do you not agree with ?.

 

Why not move the discussion forward instead of condescending responses.

 

If you lack the capability to discuss, then just state you don't understand. Will not be an issue for me.

 

Regards,

Shadders.

[adamdea]

On 8/23/2018 at 8:34 PM, John_Atkinson said:

 

You can see from the article of mine that triggered this thread an example where a perfectly legal, band-limited impulse nevertheless excites the DAC reconstruction filter's sinc-function ringing.

 

John Atkinson

Editor, Stereophile

 

I think I read your article and can’t recall a band limited impulse. Can you refer to the precise text and/or figure number. 

I don’t have the article to hand but I thought from memory it had a downward sloping frequency response but did not have an absolute frequency limit. 

Apologies if I have misremembered.

[John_Atkinson]

2 hours ago, adamdea said:

I think I read your article and can’t recall a band limited impulse. Can you refer to the precise text and/or figure number. 

 

Fig.12 at https://www.stereophile.com/content/zen-art-ad-conversion-page-2

 

John Atkinson

Editor, Stereophile

 

[Shadders]

On 8/23/2018 at 7:34 PM, John_Atkinson said:

 

You can see from the article of mine that triggered this thread an example where a perfectly legal, band-limited impulse nevertheless excites the DAC reconstruction filter's sinc-function ringing.

 

John Atkinson

Editor, Stereophile

 

Hi,

I agree, that you DO NOT require the input signal into the filter to have any out of band frequencies to cause ringing. Here is the signal analysed – this is the output of the 512tap linear phase filter. The input signal is a 1kHz sine wave, sampled at 192kHz.

 

Ringing of the filter is purely a result of the input signal second order behaviour. For example, assume the signal is at rest into the filter (0volts), and then you excite it with a sine wave starting at 0volts. At the time = 0 where the sine wave starts, you see the filter ringing behaviour. You have gone from a dV/dt=0,  to a dV/dt=Cos(phi).  This is shown in the graphic below.

As the sine wave continues to enter the filter, the ringing, which is a transient behaviour caused by the change in dV/dt, subsides to nil, and the filter outputs the sine wave. There is no ringing.

 

If at the zenith of the sine wave, where Sin(pi/2)=1.0, the signal remains at 1.0volts, here again is a change in the signal rate of change, from dV/dt=Cos(phi) to dV/dt=0. This change in the rate of change causes  transient response in the filter. This second order effect is less in the second example, and hence the amplitude of the ringing is therefore smaller. This is shown in the graphic below.

Regarding the article text “the more you constrain the data in the frequency domain, the less you can do so in the time domain, and a sinc-function filter smears the transient's energy in an extreme manner. ”

 

I would not state that the filter is smearing the transient energy. I would state it is added noise which is effectively the filter coefficients, whose amplitude is directly proportional to the second order derivative magnitude of the transients in the music.

 

Using a smaller tap filter reduces the length of the noise added to the signal, but it does not reduce the noise energy magnitude.

 

So, is all MQA proposing is the use of smaller length filters which will add less noise in terms of the length of the noise, but still adds relatively the same magnitude of noise as a longer filter ???

 

Regards,

Shadders.

[Fokus]

2 hours ago, Shadders said:

I agree, that you DO NOT require the input signal into the filter to have any out of band frequencies to cause ringing. Here is the signal analysed – this is the output of the 512tap linear phase filter. The input signal is a 1kHz sine wave, sampled at 192kHz.

 

 

You claim something, and then you try to demonstrate it with a signal that happens to have a lot of 'out of band frequencies' ...

 

[Shadders]

6 minutes ago, Fokus said:

 

You claim something, and then you try to demonstrate it with a signal that happens to have a lot of 'out of band frequencies' ...

 

Hi,

No, the signal does not have any out of band energy.

 

Can you explain why it does have out of band energy ?.

 

I recall something about the "boxcar" function ?, but cannot find the post.

 

Regards,

Shadders.

[mansr]

39 minutes ago, Shadders said:

No, the signal does not have any out of band energy.

 

Can you explain why it does have out of band energy ?.

It has wideband energy at the corners in the waveform.