Debunking "the Monty's video" (Part 2)

Confused with Part 1 of the discussion? Let me explain further...

(source: "the Monty's video", a "perfect" sine wave output)

(By the way, thanks to the discussion on head-fi, I noticed the Monty's video was removed from the official website.

 if you click on the "Digital Show & Tell" link on the web site, you'll get the following:

Hmm... why it was removed from the official site? Did someone find out it is mis-leading? The YouTube copy of the same video was uploaded to the FLStudio channel by someone else. Probably they need to ask someone to remove it and they forgot.

update: one fellow member in head-fi found out the video is somehow still available in the offical site domain However, it is not accessible from the of the main article)

As I expected, I got quite a lot of "strong" feedbacks from other people in various on-line discussions. Most of these are in the form of bullying-like argument except the one I found on head-fi (hmm... looks like that discussion is also going to the wrong direction too... I will write something about why people keep on believing in pseudoscience even they knew the flaws of their beliefs)

For most of these discussion, I feel like I am talking to people from a religious group, i.e. a group that truely believe all the contents what "the Monty's video" said. (To be honest, some parts of the video are quite interesting)

Whenver I stated some facts that is not compatiable with their "religious beliefs",  I was bullied with descriptions like mentally blocked, "flat earth supporter", etc...

In the end, I was banned totally from ASR and they had decided to remove all my comments (like virus) from their forum. 

Roon is a little bit better as they just banned me for a month and made my relevant comments hidden from the forum. (Which is still accessible from direct link here).

Anyway, let's come back to the "Debunking 'the Monty's video' (Part 2)"

What are misleading in the Monty's video?

You may say "I am confused with your part 1,  could you tell me in a few words what are misleading in the Monty's video?"

Ok, here you go:

Mis-leading point 1: perfect sine wave output? 

He emphasized "the analog output is still a perfect sine wave exactly like the original" (statement 1) at 5:03 of the video

Is the analog output really a perfect sine wave exactly like the original (i.e. is the reconstructed analog output == the original analog input?)

FACT: No, the output have some noise introduced in the ADC and DAC processes.  It is not a perfect sine wave.

Let's called the original audio signal is A_original, and the ouput of the reconstructed analog signal is A_from_DAC.

Here, A_from_DAC is not same as A_original. You could say A_from_DAC is very close to A_original but not the same. If you think they are the same, you can verifiy your defintion of "same" here.

I hope by now, you agreed that A_from_DAC is not the same as A_original.

If yes, what do you think about the statement 1 in the video, i.e. "the analog output is still a perfect sine wave exactly like the original". He used the word "perfect" to describe the output and emphasized with "exactly like" to reinforce that they are indeed "the same".  <== misleading to you?

Is the statement 1 mis-leading? You can make your judgement call here for your answer. 

For me, it is simply "mis-leading". One thing I am not sure is that I cannot tell if he doesn't know what he is talking about or he have some reasons for making such mis-leading statement. 

Mis-leading point 2: Hi-Res is useless? 

He used statement 1 to demonstrate the "fact" that Hi-Res is useless. <=== misleading

FACT: there are some noise in the reconstructed analog output. Quantization noise is one type of noise you can find in the ouput. By using more bits (e.g. 24 instead of 16 bits) for the ADC process, the quantization noise can be reduced.

You can find more info regarding the relationship between quantization noise and bitdepth in this artcile. 

In short Hi-Res helps to reduce quantization noise in the audio output when compared with CD quality digital source instead of what he suggested in the video:

 i.e. you don't need Hi-Res as CD quality can reconstruct perfect sine wave. <== misleading

Mis-leading point 3: Avoid the topic of Audio Impulse Response

In the video, he intentionally left out the discussion of Impulse Response in signal processing. 

Most modern DACs provide a list of digital filters for reconstructing the analog digital output.

For example, Topping E30 provides the following filters:

If what the "Monty's video" stated was "factual", why a modern DAC would provide so many different re-construction filter??? 

Based on the video's claim, a DAC maker, like Topping, would just need one perfect reconstruction filter for their DAC as the filter would reconstruct the perfect sine wave output. Isn't it? 

Why E30 provides so many? (Actually, these filters are provided by the DAC chip used, i.e. AKM 4493)

FACT: There is no such perfect filter mentioned in the Monty's video. All the filters above have their pros and cons. The perfect one only exist in the video presenter's own imaginary world.

For real world music reconstruction, how often you would be listening to pure 1k Hz or 10k Hz pure sine wave tone? In reality, the original audio signal is very complicated.

Different filters listed above are designed for different impulse response. 

In other words, if you have an impulse input like below:

(Note: the above graph is from google. It is not the input for the following graphs)

Which of the following reconstructed analog would be the closet to the impulse input shown above?

Output 1:

Output 2:

Output 3:

Output 4:

Output 5:

Output 6:

(source of all the above graphs: How to pick the best filter setting for your DAC – Addicted To Audio)

Which output above you would pick? For me, I would pick output 5 as it is the cloest to the impulse input.

Output 5 is the actual output of E30 with filter F-5 (i.e. Super Slow Roll-off, aka "NOS Filter"). NOS mean "Non-Over-Sampling".

Mis-leading point 4: No stair step sine wave output from 44.1k / 16 bit input?

Stair step analogy output from a modern DAC? Possible? No?

In the video, it emphasizes 44.1k /16 bit sine wave digital input would not give you stair step analog output with a modern DAC. <=== misleading.

We'd just seen in point 3 that filter F-5 have the "best" response for the impulse input (well, I hope you agree).

What would you get if you feed a perfect 10kHz sine wave digital input to a Topping E30 with filter F-5? 

Bingo! here is what you would get (the same graph I show in Part 1):

(source of all the above graphs: How to pick the best filter setting for your DAC – Addicted To Audio)

FACT: You would get a stair step audio output from a modern DAC like Topping E30 with a properly designed filter F-5

If you love to do experiment and see the stair step output yourself from a modern DAC with a properly designed filter, what you need is:

Feeding a perfect 10kHz sine wave digital input to a Topping E30 with filter F-5

In fact, it should work the same way if your modern DAC support "NOS mode" (e.g. DAC built with modern AKM chips, or Cirrus Logic chips as the NOS filter is a chip-level feature)

Conclusion: Is the "Monty's video" misleading?

Well... this is tricky. I respect your own answer regarding the question "is the video misleading". I am not going to argue with you.

From my point of view, yes, it is definitely mis-leading. It tried to hide (or avoid) something like impulse response, and mis-lead people to believe the sine wave output is perfect (which is not), and inject mis-leading idea like "no-stair step output from a DAC",  "Hi-Res is useless", etc as I shown above.

I would like to end this blog with the following picture:

(source: from "the Monty's video")

I have no doubt that the demos in the video were chosen very carefully to show what the video want you to see. Period. Cheers.