TMI about square waves

[CJ]

Cassettes sound really good to me for some reason.

What is their freq response thru a GE radio/ tape player from the 70 s?

I use it at work. I played this home made tape of John Lee Hooker off the box set over and over. 8 hours a day. For three months.

"Gonna get me some toad frog here. Mix it in real good."

 

[abbey road d enfer]

Hi folks
Really Don t know it s the right post but a fast reading makes me think this... Always used old adat recorders such as fostex ad8 and tascam mx24, this last one is so great! With not so esoteric soundcard. What I found is that even working at 44.1 16bit the sound is always bigger realistic and 3D even compared with modern high quality converters....
I believe it s the oversampling that these old vintage gital gear converters have

I believe you are jumping to conclusions that are not supported by hard evidence.
The converter technology has not changed so much, oversampling is the norm since 20+ years.

Even with modern music production, people is always excited when I mix down passing trought these devices, the answer is always the same... Hey Richi what you did?

That's what most people say when they listen to recordings made by competent people.
Don't underestimate your part.

 

[jasonallenh]

It is a weighted sum of odd harmonics. Begin with sin(x)+sin(3x)/3+sin(5x)/5 + ... The more odd overtones we add the smaller each one is and the more like a square wave the combined sum looks. The Gibbs phenomenon was caused by filtering out the HF sin(Nx)/N components above the audio passband.

JR

I used the onboard filter in my DSO to stay roughly within the audible frequencies and got this. I had no idea why anyone would measure with it! Now I at least understand what I was looking at...

 

[thor.zmt]

Rather than feed the veer already in process I thought I would start a new thread about square waves.

We use square waves and sine waves (and others) as "diagnostic" signals as they give us a reliable repetitive waveform that is easily to visualise (oscilloscope) and analyse by other means, to allow us to determine "fidelity impairments".

They are not music.

The closest "steady state" signal we can come to music is white noise that is subjected to comb filtering.

Test signals and instrumentation to analyse them are kind of like a map. They show you the way, but they are not the way.

Back in the 70s(?) some people tried to name new distortions based on this phenomenon. I was not a fan nor were some old school guys who cut their teeth designing HF radar technology during WWII.

That doesn't mean the distortion did not exist. It doesn't care if you are fan or not.

What we do with specific test signals and methods is to try to make audible fidelity impairmets quantifiable using technical/mechanical means.

An important issue here is to remember that there are very tenuous links between fidelity impairments in the sense of signal theory and fidelity impairments in an audible sene.

Obsessing about specific test methods and the outcomes WITHOUT sufficient reference to audibility is pointless and unconstructive.

Thor

 

[thor.zmt]

I know I am being pedantic but a perfect square requires an infinite bandwidth to pass it unchanged, it does not of itself posses a bandwidth. However, its Fourier expansion is an infinite number of sine waves. Slew rate applies to any network, even passive ones; it is not necessary to add an op amp or any active component. Audio circuits do not need a very high slew rate to be able to pass a 20KHz bandwidth. The fastest you need to go is from the top to the bottom of a 20KHz sine wave which is a period of 25uS. So if you want to output +20dBu = 21.917V peak to peak at 20KHz you only need to be able to slew 22V in 25uS which is less than 1V per uS.

Sample rate is 48kHz.

A full scale 20kHz sinewave will be encoded as set of current steps.

As we have 48/20 = 2.4 Samples per 20kHz cycle we will see amplitude modulated square wave with a 48kHz base frequency, like so.



Obviously the edge rate of these currentsteps is very large, much,much, much larger than full scale in 25uS.

Thor

 

[abbey road d enfer]

I gave up following this thread 9 months ago.

 

[jasonallenh]

I gave up following this thread 9 months ago.

If it's any consolation, I learned a few things a couple pages ago