Transformers

[Geoff_T]

Oops, then I got your preamp confused with someone elses... sorry about that.

<snippety>

Also, I've been using the Avalon Design U5 DI when recording and I love it... but I've been thinking about trying something else lately... does your preamp have an instrument input... and if so, does it kickass on bass? I'm stuck at work in the office right now and dicking around... please post a link to your preamp. Thanks again.

Hi

Not only has our preamp got a DI (it has two actually) but it also has two outputs per channel ... a balanced and unbalanced at the same level.... so splitting to two destinations is easy.

The DI input impedance is 10 million ohms so, as far as your guitar is concerned, it's connected to an open circuit... you would hear sounds that you've never heard before!

Here's a link.....



http://www.auroraaudio.net/aa_html/aa_products_gtq2.html

 

[DJL]

Super... I'm headed that way on the link now. Thanks

 

[DJL]

Wow, all the heavyweights are coming out of the woodwork... Hi Dan Kennedy, I see your onboard with us now too... please join in. Thanks

 

[regebro]

The problem with digital is that, like power amps, they measure noise from the maximum output down... rather than referencing it to 0dBu.

In digital, that's the same thing.

OK, so a Neve console has a dynamic range of maybe 153db. OK. Cool. And a 24bit digital console has a dynamic range of 146db.

So, what is your point? That digital should go up a couple of bits and use 28? Well, fine, but the analog tape were using doesn't have anywhere near this dynamic range anyhow. And in the end it ends up on a CD, that has 98db range anyhow...

Both 24bit digital and Neve consoles has loads of margins to play with.

 

[regebro]

Got any idea what the frequency of an atomic clock is? Just curious if you know how often they "sample" the radiation.

Or is it just calibrated and used at the half-life of the element????

There is no radiation involved. Most atomic clock are based on Cesium-133 which isn't radioactive.

Let's see <googling>... Cesium 133 oscillates at a rate of 9,192,631,770 cycles per second. Exactly. Because this is nowadays the definition of a second; the time is takes for Cesium 133 to oscillate 9,192,631,770 cycles.

 

[regebro]

Can we hear subtones of higher frequencies?

No, becuase the whole concept of "subtones" doens't make any sense in this context.

Fletcher has an article about a bad module ringing at something like 60K that was detected by Geoff Emerick because it just didn't sound right.

If the module simply would have added a 60kHz tone it should not have been audible. In fact, I doubt it would have gone very far in the signal chain at all.

However, if that 60k tone somehow was generated in a way that also somehow modified the other signal, for example by amplitude modulation, other tones would have been created that would have been audible. The same thing does for if the input signal modulated that 60k tone, which maybe is even more likely.

 

[Geoff_T]

No, becuase the whole concept of "subtones" doens't make any sense in this context.


If the module simply would have added a 60kHz tone it should not have been audible. In fact, I doubt it would have gone very far in the signal chain at all.

However, if that 60k tone somehow was generated in a way that also somehow modified the other signal, for example by amplitude modulation, other tones would have been created that would have been audible. The same thing does for if the input signal modulated that 60k tone, which maybe is even more likely.

Hi

That story gets so corrupted....

All it was was that the 1K5 + 10nF R/C network on the output transformer had come unsoldered. The effect would be the same as the unterminated modules I mentioned earlier... a boost of around 10dB at upwards of 40KHz.

They would have been playing music and he would have noticed the sibilance on that output.

From this dry joint a whole range of topics has been spawned.

 

[c7sus]

It's what makes audio FUN!

 

[c7sus]

My question about atomic clocks was aiming at exactly how they come to determine something oscillating at such a high rate.

How do you measure an event occuring at less than 1/9MILLIONTH of a second?

Is it a mathematical calculation, or are there instruments that can actually measure over 9MILLION oscillations/second???

Which I got the idea to ask about atomic clocks because I remember at one time DK posted he got his start in designing process controls and instrumentation, and his comment that amplifying instrumentation signals isn't that far removed from amplifying audio. Both have applications where accuracy of the amplified signal can be paramount.

Anyway, I thought it was a cool analogy..........

 

[HangDawg]

My question about atomic clocks was aiming at exactly how they come to determine something oscillating at such a high rate.

How do you measure an event occuring at less than 1/9MILLIONTH of a second?

Is it a mathematical calculation, or are there instruments that can actually measure over 9MILLION oscillations/second???

Which I got the idea to ask about atomic clocks because I remember at one time DK posted he got his start in designing process controls and instrumentation, and his comment that amplifying instrumentation signals isn't that far removed from amplifying audio. Both have applications where accuracy of the amplified signal can be paramount.

Anyway, I thought it was a cool analogy..........

That's 9 billion baby, Billion

 

[Geoff_T]

That's 9 billion baby, Billion

Most computers are working in gigahertz now!



Geoff

 

[regebro]

My question about atomic clocks was aiming at exactly how they come to determine something oscillating at such a high rate.

Good question. And of course, today, it's relatively simple, with the high-speed technology used for computers. But when the first cesium clock was made in 1952 this was not available.

However, the trick is division. The prime factors of 9,192,631,770 are 2, 3, 3, 5, 7, 7, 47 and 44351. Dividing by small numbers are easier than dividing by large, so by first dividing the signal with two, and then three, and then three again, and so on, you can get the signal down to a frequency where you are able to build a counter. I would guess that counter would be 47*44351 large, that it 2 084 497. That counter would have to be running at just above 2 MHz. If this was possible in 1952 or if they used other clever tricks I don't know.

Maybe it's possible to build an accurate "divider by 47" without using counters, and then they could use a counter only for the largest prime. That counter would only have to run at 44kHz, something that surely should be trivial even with the tubes of 1952.

 

[c7sus]

9 BILLION! Yeah.

Sorry, I was on the phone with a couple fuckwits from the IRS this morning and was so pissed I couldn't see straight afterwards.

Tip: file your taxes and PAY them BEFORE you die.

It will save your kids about 3 years (and counting) worth of bullshit after you're long gone.

 

[chessrock]

the trick is division. The prime factors of 9,192,631,770 are 2, 3, 3, 5, 7, 7, 47 and 44351. Dividing by small numbers are easier than dividing by large, so by first dividing the signal with two, and then three, and then three again, and so on, you can get the signal down to a frequency where you are able to build a counter. I would guess that counter would be 47*44351 large, that it 2 084 497. That counter would have to be running at just above 2 MHz. If this was possible in 1952 or if they used other clever tricks I don't know. Maybe it's possible to build an accurate "divider by 47" without using counters, and then they could use a counter only for the largest prime. That counter would only have to run at 44kHz, something that surely should be trivial even with the tubes of 1952.

Hey DJL, aren't you glad you asked that Analog vs. Digital question ? ? ! ! !

Just wait. It gets better. Trust me!

 

[Harvey Gerst]

Yea, DJL. I do this kind of shit all freakin' day long.

Just for my sheer amuzement.

The interesting thing about how digital sampling works at very high frequencies isn't so much in how high it can go . . . it's mainly in it's very nature of how the wave is going to be represented. It's kind of like playing a connect-the-dots game as opposed to making a smooth, fluid drawing of a wave. I don't know if it's nearly as much of an issue as people make it out to be, though.

Maybe you can answer a question about digital that's been puzzling me. Let's start with a frequency of say 7,500 Hz. To make it interesting, let's make it a square wave.

Now as I understand it, a square wave is simply a sine wave with all the odd harmonics (3, 5, 7, 9, ....) included, in a diminishing intensity, and a a sawtooth wave is simply a sine wave with all the even harmonics (2, 4, 6, 8, ...) included, also in a diminishing intensity.

That seems to mean that the third harmonic of this 7,500 Hz square wave (at 22,500 Hz) is outside the limits of Nyquist, and is therefore thrown away or ignored.

Which means to me that digital can't reproduce square waves above 7,500 Hz - they just come out as sine waves above that frequency. Am I missing something here?

It gets weirder. A sawtooth wave (all even harmonics) fairs a little better, but becomes a pure sine wave above 11,100 Hz.

If those statements are indeed true, it sounds like 44.1 digital will only go up to 7.5 or 11.1 before it changes everything to pure sine waves. Yes? No? Kinda?

This has been bugging me for a while now.

 

[chessrock]

If those statements are indeed true, it sounds like 44.1 digital will only go up to 7.5 or 11.1 before it changes everything to pure sine waves. Yes? No? Kinda?

This has been bugging me for a while now.

I'm not going to pretend to be an expert on this stuff, but it sounds like you're on the right track. Whether or not it happens exactly as you say, it's probably safe to assume it does funny things in the higher freq's.

The guy to ask would be Ethan Winer. He seems to be the resident expert when it comes to this sort of thing. Although I haven't seen him posting around these parts in a while -- I'm assuming his Realtraps business must be coming along, which would be good news. McQuilkin would probably know something.

 

[crazydoc]

If those statements are indeed true, it sounds like 44.1 digital will only go up to 7.5 or 11.1 before it changes everything to pure sine waves. Yes? No? Kinda?

Interesting thoughts, Harvey. I don't know the answer, but it seems everything would be turned into little stairsteps at the sampling rate, which if smoothed would resemble sine waves.

This brings up several other questions in the analog realm:

1)Assuming you could get a 7500 Hz square wave into the air (I don't know that any speaker could faithfully reproduce an electronic square wave at that frequency), if you recorded it (analog) with any of the usual suspect microphones that drop off after ~20kHz and then examined it on a scope, would it look more like a sine wave (or at least a square wave with very rounded corners)?

3) If you could switch back and forth between 7500Hz square and sine waves faithfully reproduced from a loudspeaker, could the human ear/brain tell the difference?

 

[regebro]

Which means to me that digital can't reproduce square waves above 7,500 Hz - they just come out as sine waves above that frequency. Am I missing something here?

It gets weirder. A sawtooth wave (all even harmonics) fairs a little better, but becomes a pure sine wave above 11,100 Hz.

If those statements are indeed true, it sounds like 44.1 digital will only go up to 7.5 or 11.1 before it changes everything to pure sine waves. Yes? No? Kinda?

No, you are completely correct. But remember, this goes for *all* equipment that can't reproduce frequencies higher than 20kHz.

 

[freshmattyp]

I just have to say this is a facinating read, and it's nice to see all of us playing together so well. There must be some bad mojo over in the "M" forum.

 

[DJL]

Hey DJL, aren't you glad you asked that Analog vs. Digital question ? ? ! ! !

Just wait. It gets better. Trust me!