Transformers

[Harvey Gerst]

A lot of analog equipment goes out well past 20k. My JBL 075 tweeters are pretty flat out to 30k, then drop off smoothly from there. I have an old Telex reel to reel that's flat to 37k, then rolls off from there.

But we're not talking about gradual rolloffs with digital - at 22.05 kHz, the signal goes thru a brickwall low pass filter that chops everything above that frequency drastically.

So the question remains; is there an audible tonal difference between a 7.5 kHz square wave and a sine wave? Is there an audible tonal difference between a 11.5 kHz triangular wave and a sine wave? Does digital turn them both into pure sine waves above those frequencies?

Is it audible? Is it important? Does that contribute to some of the differences we hear between digital and analog?

Is digital sound only accurate on CDs with sounds that are below 7,500 Hz, if those sounds contain odd harmonics? It's a lot lower frequency if the fifth harmonic is important; that's around 4,500 Hz with a square wave.

I don't have any answers, but I do have some nagging suspicions. Anybody?

 

[DJL]

So is it ok to connect a High-Z device output (bass guitar) to two High-Z inputs (two bass amp) without loading down the bass or the amps?

 

[DJL]

A lot of analog equipment goes out well past 20k. My JBL 075 tweeters are pretty flat out to 30k, then drop off smoothly from there. I have an old Telex reel to reel that's flat to 37k, then rolls off from there.

But we're not talking about gradual rolloffs with digital - at 22.05 kHz, the signal goes thru a brickwall low pass filter that chops everything above that frequency drastically.

So the question remains; is there an audible tonal difference between a 7.5 kHz square wave and a sine wave? Is there an audible tonal difference between a 11.5 kHz triangular wave and a sine wave? Does digital turn them both into pure sine waves above those frequencies?

Is it audible? Is it important? Does that contribute to some of the differences we hear between digital and analog?

Is digital sound only accurate on CDs with sounds that are below 7,500 Hz, if those sounds contain odd harmonics? It's a lot lower frequency if the fifth harmonic is important; that's around 4,500 Hz with a square wave.

I don't have any answers, but I do have some nagging suspicions. Anybody?

I'm no expert, but I can hear a difference between the different wave forums... although the higher the freq gets the harder it is to hear the differences. I'm referring to using a synth when listening... so I'm not sure if it applies to your digital question?

 

[chessrock]

But we're not talking about gradual rolloffs with digital - at 22.05 kHz, the signal goes thru a brickwall low pass filter that chops everything above that frequency drastically.

Apparently, this used to be the case . . . before oversampling converters. I don't know how it all works but apparently oversampling is supposed to correct a lot of this -- and it appears to be quite common in most A/D converters from what I gather.

 

[Geoff_T]

Apparently, this used to be the case . . . before oversampling converters. I don't know how it all works but apparently oversampling is supposed to correct a lot of this -- and it appears to be quite common in most A/D converters from what I gather.

Hi

I'm not an expert on digital but was led to believe that if you use 44.1KHz you have to roll of the audio at around half that (22KHz) with a filter of around 96dB/octave = brick wall = bye, bye harmonics.

Geoff

 

[regebro]

A lot of analog equipment goes out well past 20k.

And so does a lot of digital equipment. A 24/96 A/D concerter should be able to be totally flat up to 40 kHz without any real problems.

But we're not talking about gradual rolloffs with digital - at 22.05 kHz, the signal goes thru a brickwall low pass filter that chops everything above that frequency drastically.

Nah, because nowadays you oversample the inputs, so you can have nicer filters. Don't remember the details, though.

So the question remains; is there an audible tonal difference between a 7.5 kHz square wave and a sine wave?

I'm gonna do some testing on this when I get my stuff down here, just for fun. I'm gonna see how high up I can hear the difference for example. With analog and digital. This will take a couple of months, though.

Is it audible? Is it important? Does that contribute to some of the differences we hear between digital and analog?

My personal guess is "no" and all of the above. This is, at least in theory, very minor issues in the differencies. I could be wrong though. Real scientific testing on this would be fun to do, but I don't have the resources,

 

[chessrock]

I'm not an expert on digital but was led to believe that if you use 44.1KHz you have to roll of the audio at around half that (22KHz) with a filter of around 96dB/octave = brick wall = bye, bye harmonics.

Im far from an expert myself, but I remember hearing something about how oversampling was supposed to address this problem.

 

[Harvey Gerst]

I can see how oversampling might reduce in-band, unwanted artifacts, but as near as I can understand it, a standard CD cannot reproduce any frequency over a little less than 1/2 the Nyquist frequency, which for a CD is 22,000 Hz.

That means the entire overtone chain of a 7,500Hz square wave will be missing, and the second harmonic of a 4,500Hz square wave (and all the rest of the harmonic chain) won't be reproduced either. Oversampled or not, those frequencies are out of the bandwidth of a normal CD.

For a square wave, that seems to means that CD accuracy stops at 7,500Hz; for any other kind of wave, accuracy stops at 11,100Hz; everything comes out as a sine wave above these frequencies. Cymbals and trumpets have overtones that extend to well over 40,000 Hz.

My main question is: Are the lack of these overtones perceived as an audible difference? Is there an audible difference? And is the difference important?

 

[regebro]

I can see how oversampling might reduce in-band, unwanted artifacts, but as near as I can understand it, a standard CD cannot reproduce any frequency over a little less than 1/2 the Nyquist frequency, which for a CD is 22,000 Hz.

No, it can't. But with oversampling you don't have to have horrible brickwall analog filters.

But of course, a CD can't reproduce these frequencies no matter how the were originated, analog or digital.

 

[chessrock]

But of course, a CD can't reproduce these frequencies no matter how the were originated, analog or digital.

Alright, then, guys. Looks like that settles that. We're basically screwed either way unless the record industry decides to go back to cassette.

Anyone want to talk about transformers ? ?

 

[Geoff_T]

No, it can't. But with oversampling you don't have to have horrible brickwall analog filters.

But of course, a CD can't reproduce these frequencies no matter how the were originated, analog or digital.

Hi

My brain itches....

So, with oversampling, what is the highest audio frequency it can sample?

 

[crazydoc]

So the question remains; is there an audible tonal difference between a 7.5 kHz square wave and a sine wave? Is there an audible tonal difference between a 11.5 kHz triangular wave and a sine wave?

I'd still be interested to know if the human ear can distinguish between a square and a sine wave at 7.5kHz (or sine and triangle above 11.5k). My gut feeling is that it can't, because the the first distinguishing feature between the two, the 3rd order harmonic, is outside of the frequency range of human hearing.

Another distinguising feature would be power, since a square wave at a given frequency contains ~1.4 times the power of a sine wave. Would this be perceived as gain, or would this extra power be contained in the 3rd order and higher harmonics and not be heard?

Whether the ear can or can't hear the difference in square and sine at 7500Hz, at what frequency is the difference perceptible?
How can we test this?

 

[regebro]

Give me some really fucking good speakers, mics and preamps, any even half-decent test oscillator, an oscilloscope and a big piece of thick fabric to block the view with, and we'll soon figure it out.

I trust the Earthworks stuff. Buy it and have it shipped over to me.

 

[crazydoc]

Give me some really fucking good speakers...

Well, I've got everything but these, so when someone sends them to me I'll let you know how it comes out.

 

[regebro]

Well, I've got everything but these, so when someone sends them to me I'll let you know how it comes out.

You got earthworks mics and preamps? "Good" in this contexts means "accurate" not "sounds great".

 

[crazydoc]

You got earthworks mics and preamps? "Good" in this contexts means "accurate" not "sounds great".

Well, I have a Behringer ECM8000 which only drops off 10dB@30k, and I'm sure I could EQ my MQ3 enough to square up a 7.5k square wave. But, I don't really need these - I can input the square wave or sine from my signal generator into an amp - it's the speakers that would need to be accurate.

 

[DJL]

QUOTE]Originally posted by regebro
Yes, and loads of homerecorders today record their guitars via the all-digital Guitar Pod. So, if tubes are better than transistors and analog sound better than digital, then how come guitarists like the Pod?[/QUOTE] Oh yeah, and I forgot to comment on this. Good question... mabye because they can't play very loud where they live, or maybe because they can't afford a tube amp, or maybe they don't have the space for an amp, or maybe they don't play live and don't want an amp, maybe they've never played through a real amp... it beats me why.

 

[DJL]

Anyone want to talk about transformers ? ?

Isn't the transformers a kids cartoon?

Come on cress, this is a good thread, don't put the fire out yet.

 

[regebro]

Well, I have a Behringer ECM8000 which only drops off 10dB@30k

Being Earthworks ripoffs they could work fine.

But, I don't really need these - I can input the square wave or sine from my signal generator into an amp - it's the speakers that would need to be accurate.

And how do you know they are, unless you have a mic and preamp that can verify it?

You need to have a scope where you can verify that the square signal indeed is at least a bit square even after passing through the speakers.

 

[regebro]

Yes, and loads of homerecorders today record their guitars via the all-digital Guitar Pod. So, if tubes are better than transistors and analog sound better than digital, then how come guitarists like the Pod?

Oh yeah, and I forgot to comment on this. Good question... mabye because they can't play very loud where they live, or maybe because they can't afford a tube amp, or maybe they don't have the space for an amp, or maybe they don't play live and don't want an amp, maybe they've never played through a real amp... it beats me why.

Yeah, thats good. All data that doesn't fit with the theory is an anomaly.