Square Wave Testing of Audio Products (Video Tutorial)

[HP9000]

Where things fall apart is how correlated a "near perfect" square wave is with perceived sound quality. In an extreme case if you look at a 10 Khz square wave reproduced by a high quality class D amp and a wide bandwidth class AB you would conclude the class D amp would sound terrible but that is not the case. Just like SINAD, which is also limited in it's ability to predict perceived sound quality but has it's place, a square wave also has it's limits to predict perceived sound quality.

Square wave capability may be less relevant at higher frequencies as I stated, and in the thread I referenced I said that the treble response linearity/square wave can be an inevitable byproduct or simply what it takes to achieve a good response for the lower ranges where most music frequencies are based and where it matters.

It seems like you are claiming some type of "conspiracy" to cover up square wave testing to keep people in the dark. I do see what some could perceive as heavy handed moderating which usually happens when someone make a "scientific claim" such as better square waves sound better but can't back it up with some evidence of perceived sound quality in blind testing. In the name of not confusing people posts are deleted and in some cases people are banned.

To me when talking about amps everything comes back to blind testing and perceived sound quality in order to determine what is "good enough" and at that point move on to something else like better speakers rather than chasing around things that you can't hear.

I have the suspicion that the query for a blind test is overused and is a cop-out e.g. for when there is no reason to think that people would report differently in one compared to just frankly stating their listening experiences outside of one. This suspicion is further raised when I see people not lamenting that there is no blind test to refer to and are instead giddy going right to the conclusion that the matters are trivial, and when they are not equally interested in one being conducted, instead telling me that if I want one I should do it myself. Blind testing provides confirmation, but it's still based on doubting people's perception. It has to exist because of the people who are tricked in their mind. I think that appealing to psychology to dismiss people reporting audible differences is also done unfairly.

I can see both sides of this and think ASR does OK in general but the one thing that seems inconsistent to me is that SINAD is seldom if ever held to the same standard. The excuse is "better SINAD means better engineering" but that is not necessarily true as what is the point of spending extra money on better SINAD if it doesn't make any difference for it's intended use? When it comes to "square waves" it could certainly be argued that it is "better engineering" if class D amps could reproduce near perfect 10 Khz square waves but again why bother if it is not important for perceived sound quality.

It's not even about the tests backing purchasing decisions, it's about how the some tests are taken and published in the final review, yet some aren't. If both are being said to show better engineering, then why is one being excluded, especially considering:

Anyone who doesn't appreciate the power and value of square wave testing to confirm an amp is working as expected or not and to diagnose problems quickly and efficiently needs to do some research as I think this is as close to a fact as there can be in the audio world.

 

[levimax]

Square wave capability may be less relevant at higher frequencies as I stated, and in the thread I referenced I said that the treble response linearity/square wave can be an inevitable byproduct or simply what it takes to achieve a good response for the lower ranges where most music frequencies are based and where it matters.



I have the suspicion that the query for a blind test is overused and is a cop-out e.g. for when there is no reason to think that people would report differently in one compared to just frankly stating their listening experiences outside of one. This suspicion is further raised when I see people not lamenting that there is no blind test to refer to and are instead giddy going right to the conclusion that the matters are trivial, and when they are not equally interested in one being conducted, instead telling me that if I want one I should do it myself. Blind testing provides confirmation, but it's still based on doubting people's perception. It has to exist because of the people who are tricked in their mind. I think that appealing to psychology to dismiss people reporting audible differences is also done unfairly.


It's not even about the tests backing purchasing decisions, it's about how the some tests are taken and published in the final review, yet some aren't. If both are being said to show better engineering, then why is one being excluded, especially considering:

I don't disagree with anything you are saying except that you place more value in uncontrolled listening and in my personal experience unless you level match and do them blind listening tests are unreliable to the point of being useless. While @amirm doesn't owe anyone anything and his testing is an invaluable service to everyone I can see the value of doing the same tests for every amp. I think the main reason many feel square wave testing is not necessary is that anything you can learn from a square wave is shown in the other tests if you know what to look for without getting into the "bandwidth limited" rabbit hole.

 

[HP9000]

@levimax
I do not place more value in uncontrolled listening. I am recognizing that there being no test does not equal there being no difference. Better yet, there being no test that shows a difference cannot be equivocated with there being a test that shows that there is no difference when talking about audibility.

"Anything you can learn from a square wave is shown in the other tests if you know what to look for" It still doesn't work to think that its exclusion is in the name of avoiding redundancy when the square wave shows you so much at once, making it redundant to include some others.

I'm supposed to think people would have reacted better to me speaking on a subject that I am more prepared to speak on where my thoughts are more collected, yet that would mean talking about how Hoffman's Iron Law is false (and not just from a 'small, bass capable, inefficient speaker with a class d amp' perspective), which would garner a worse reaction faster.
I just reread through the Mscaler thread starting from my first post to the most recent. Others were spamming the same video and posting memes yet I get silenced for "not understanding" and "taking up space". Seeing that people are allowed to quote me and continue on with the subjects I brought up and yet I am not allowed to reply to make corrections, honestly screw @amirm and his cronies and @BDWoody especially with the Kafkaesque bug-eyed stoner-eyes Scooby-Doo with blunt in paw and wad of cash picture.

 

[amirm]

"Anything you can learn from a square wave is shown in the other tests if you know what to look for" It still doesn't work to think that its exclusion is in the name of avoiding redundancy when the square wave shows you so much at once, making it redundant to include some others.

It doesn't show you more at once. It shows you things that are non-issues. It also is highly obscure in some aspects like bandwidth limiting which frequency response shows with ease.

Square wave tested was used when all an engineer had was a scope. Now we have specialized audio measurement gear that does the job properly and far, far more clearly.

Seeing that people are allowed to quote me and continue on with the subjects I brought up and yet I am not allowed to reply to make corrections, honestly screw @amirm and his cronies and @BDWoody especially with the Kafkaesque bug-eyed stoner-eyes Scooby-Doo with blunt in paw and wad of cash picture.

With that kind of language, you don't belong here no matter what you want to say. I suggest taking your own advice and moving on to other fora where such conduct is allowed.

 

[amirm]

Many here just have no idea about it. Too many armchair experts around.

Yeh, I count you in that armchair brigade.

 

[BDWoody]

honestly screw... @BDWoody especially...

I'm all booked up, but thanks for the referral.

You can move along now.

 

[restorer-john]

What on earth is going on here? Must be a full-moon or something?

 

[fpitas]

honestly screw @amirm and his cronies and @BDWoody especially with the Kafkaesque bug-eyed stoner-eyes Scooby-Doo with blunt in paw and wad of cash picture.

Gotta say, that's obviously intended to be rude, but creative to the point that I have no clear idea what he's saying. I think he's mad...

 

[solderdude]

Let's bring it back on topic..

Engineers like to use square-waves because it can show a lot of things (most of all FR issues) with just 1 or 2 different frequency square-waves with one quick glance at their oscilloscope within a few seconds.
Furthermore, it is also very easy to see changes when applying a (difficult) load directly at a single glance at a scope image. All the way from DC to MHz region with cheap gear.
So... very handy for an engineer. I use them as well for the above reason, a quick glance at certain aspects, but not surprisingly am an engineer without an armchair.
This is sooooo much faster than running sweeps (automated or not) when starting to testi/trouble shoot .

Does it tell you more than some full sweeps in FR (if the analyzer could reach that far), phase and distortion ... no.
That could be a reason not to use square-waves when one is going to run a full measurement suite anyway which can dive much deeper than a scope image.
That scope image is linear in amplitude yet our hearing is logarithmic. So small level signals aren't seen but small variations in the signal itself are easy to spot.

Rise and fall times of the square-wave (so zoomed in a LOT) can show specific problems at a single glance certainly with audio gear that has a lot of overall feedabck.
At least to engineers with enough knowledge/experience. Someone with little to no knowledge would have to be explained what to look for and why.

So yes, engineers do love square-waves and for good reason. For this reason engineer type people (regardless if they are considered armchair or not) would like to see a screen shot of a low and higher frequency square-wave... at least for amplifiers (so analog plane).

The question is are they essential and are they needed on top of a full FR/phase/distortion analysis under various loads where the FR is tested far enough ?
I have to agree with @amirm here. They are not an essential measurement that must be there all of the important info is there in other measurements, or at least can be.
Square-waves are just very handy for engineers that like to see several factors at a quick glance.

No need to get tied in a knot over this and certainly not to dis other people, regardless who they are.

 

[pma]

Yeh, I count you in that armchair brigade.

Number of produced and tested electronic boards by myself is in thousands and the number of designed boards is more than one hundred. So, maybe a sort of armchair, if you wish. Not mentioning measurements on HV circuit breakers and plasma torches.

 

[solderdude]

You could turn it into a joke by stating the office chair you sat on during your testing and manufacturing indeed had arms. Mine has... at least some of them had over the years.

 

[KSTR]

Number of produced and tested electronic boards by myself is in thousands and the number of designed boards is more than one hundred. So, maybe a sort of armchair, if you wish. Not mentioning measurements on HV circuit breakers and plasma torches.

For a moment I was tempted to flag Amir's insulting comment to a moderator but then then again, I think he's just a little stressed at the moment and filed it under "farting".
Good to see you kept calm and stand above such incidents.

 

[pma]

For a moment I was tempted to flag Amir's insulting comment to a moderator but then then again, I think he's just a little stressed at the moment and filed it under "farting".
Good to see you kept calm and stand above such incidents.

Take it easy . That's the only way how to survive on the forum .

 

[restorer-john]

For a moment I was tempted to flag Amir's insulting comment to a moderator but then then again, I think he's just a little stressed at the moment and filed it under "farting".
Good to see you kept calm and stand above such incidents.

Same here. Moving/selling houses is second to/worse than a divorce. Cut the guy some slack.

 

[jxdking]

Square wave is a very useful tool to validate the stability of the amp. Before the test, make sure to remove the input filter if there is any. If you are not the designer, it may not be practical to remove the input filter.

 

[pma]

Yes. Square wave testing is one of the most important test during design and prototype phases of analog amplifiers and also very important to check for stability. I understand that those who have never designed any analog amplifier and their career was spent in digital circuits design may underestimate or not understand importance of square wave testing. It does not need to be necessarily a square, voltage step with shortest rise time is what we need.