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How a cartridge works

DDF

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Cheers. Looks like I am in for a fair bit of reading. Good. As for rabbit holes, happening on this site was to trip down one rabbit hole, and now I see that lining it are doors into other rabbit holes. All I want to do is understand one thing at a truly fundamental level, but I suspect that while I will not run out of rabbit holes I will run out of time.

Start with these Audio articles then. Those Audio articles were meant for magazine readers, laymen short on time and attention span, but savvy enough to understand the basic technical descriptions and interested enough to work through the few short pages in order to get down the basics.
 

sergeauckland

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Cheers. Looks like I am in for a fair bit of reading. Good. As for rabbit holes, happening on this site was to trip down one rabbit hole, and now I see that lining it are doors into other rabbit holes. All I want to do is understand one thing at a truly fundamental level, but I suspect that while I will not run out of rabbit holes I will run out of time.
I've been going down audio rabbit holes for some 55 years, and still find new ones, so take heart. Once you think you understand one thing, it leads to another then another. Web surfing is just a subset!

S
 
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TG1

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Watch this interesting demonstration:

"In this video I experiment with Lenz's Law And Faraday's Law of Induction to generate electricity and magnetic force fields in copper. "


Fascinating video, thanks very much.
 
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TG1

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Exactly, no power supply, because none is needed. The process in the cartridge is basically the same as a process in electric generators where the kinetic energy of water or wind is converted into electric energy. Lenz law is saying that generated voltage is proportional to the change of magnetix flux that cundoctor is experiencing, and here is not important if magent is fixed and conductor is travelling or vice versa. So yes, the voltage itself takes on the form of moving pattern. I don't think anybody really knows why is that happening, but we do know how, so we are using it. :D



As I said, I don't think we know why is that happening - all we know is that generated voltage is proportional to the speed and direction of movement of either magnet or the coductor.

Btw, here you should also know that matrix for the gramophone record is generated by the opposite process. Generator and motor are basically the same device: one is used to produce electrictity from the kinetic energy (movement) and the other produces movement from the electric energy. So, the matrix for the graophone record (which is used in a pressing process to maker records) is produced in a motor-like fashion: music is played via amplifier which produces enough voltage to shake the needle proportionaly to the voltage pattern which then leaves the same pattern imprinted into a soft material of the matrix, which hardens afterwards. Process of playing the record is a reverse of the process of making a matrix for the record. :)

Well, isn't that extremely interesting? So the analogue process is maintained even down to the electrical current taking on the form of the original sound wave. Essentially, then, the moving magnet writes into the electrical current the waveform, like I would write a word on a piece of paper. All the while transformations in scale must be occurring because the original waveforms must be on a larger scale than those embedded in the electrical current as it passes down the wire.

Ok, I think I have hit a wall. The movement of the magnet induces a current of electricity in the copper coil (or the movement of the coil around a stationary magnet does the same thing) and as the magnet moves the wave form that is embedded in the record groove is inscribed 'somehow' into the electrical current, and the current carries that waveform down the line.
The only way I can picture it is as the electricity conforming to the shape of the wave like water conforms to the shape of a wave.

Even people who understand this stuff know that it happens and how it happens but not why it happens.
 

LTig

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On the other hand digital sampling does not reproduce the pure waveform (it seems) but only a computer generated waveform based on the limited sampling. So the programme must predict what is in the gaps between samples. I know he said the human ear can't distinguish between the two once a certain frequency of sampling is used, but it surely remains a fact that the two waveforms are not identical,and therefore the music listened to is not the same.
I know I am working my way through a thought process long since settled among members here, so thanks for the tolerance.
Painting the digitized samples into a graphic and connecting the samples with lines, or drawing horizontal lines the length of a sample period and connecting those with vertical lines is not how the signal looks like once it has left the DAC and the following reconstruction filter! Showing such graphs is misleading, and better text books show single data points (which does not prevent one from drawing invisible lines between data points and thinking that this the analog signal - it isn't).

The best way to demonstrate this is to feed an AD-DA chain with a 20 kHz sinus signal and look at both input and output with a dual channel oscilloscope. You will not see any gaps or steps, just a pure sinus at the output.

The only difference between input and output is that those components of the input signal whose frequencies are equal or higher than half of the samplerate get lost - they have to be removed by the anti aliasing filter in front of the ADC.
 

RayDunzl

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Even people who understand this stuff know that it happens and how it happens but not why it happens.

At some point in all investigations of physical phenomena you can drill down to the area where there is no answer to why.

Why electrons?

Why fields?

Why anthing?
 

LTig

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Thanks very much - very interesting. Looking at that first video one would think - despite what he says about digital and vinyl being the pretty much the same - that digital would outperform vinyl just because there are fewer (as far as i currently know) gaps in the chain to bridge. Wouldn't it be the case that every time the signal has to be translated it is bound to suffer some loss of integrity?
Yes, but transformations within the electronic domain (analog - digital - analog) have much lower loss then transformations between the electronic domain and other domains:
  • electronic - air pressure, e.g. microphones/speakers
  • electronic - mechanics, e.g. vinyl cutting stylus/playing stylus.
  • electronic - magnetics, e.g. tape heads
Not long ago @Blumlein 88 posted several pieces of music which were transformed 8 times from digital to analog and back to digital, and very few people could here the difference. This is not possible with analog tape, vinyl, or microphones and speakers.
 
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TG1

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Thinking about this:

The voltage is generated as the coil/magnet move relative to each other, and the magnetic field "moves" through the electron field.

No voltage is generated when the coil and magnet are at rest relative to each other, even if "deflected" at that time.

Push the stylus and hold - there should be a hump of voltage coming back to zero, as the coil and magnet move relatively and come to rest.

Push the stylus and release - there should be a hump of voltage coming back to zero at the peak of the movement (at rest again) and then an opposite hump of voltage.

View attachment 27670

Sorry, I don't sketch well with a friggin' mouse.

The groove of the record may not look like what you would see on an oscilloscope, rather, it encodes the motion required to create what is seen on a scope.

On the other hand, when you graph digital, what you see are the voltage levels - what you see in a digital wave is what should be seen on the 'scope.

Someone else can likely explain this better, or tell me I'm all wet, or have some better visual examples.

I will need to do some reading before I can understand that but thanks for the explanation. I think that ought to be my next step before I come back to this.
 

RayDunzl

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Maybe not to complicate too much and stick to the statement that the voltage looks like the slope of the groove - at points of the groove where slope is low the voltage is low, where the slope is high the voltage is also high.

Condenser (capacitive) vs Dynamic (diaphragm and voice coil) Microphones exhibit a similar difference...

"The waveform of the output of a condenser microphone is directly related to the sound pressure of the sound wave. The waveform of the dynamic microphone is related to the velocity of the sound wave. When the pressure hits the peak, the speed of the air molecules is zero. At this point, the condenser signal is at max, and the dynamic signal is zero.

In general, there is a 90° difference between the signals from a condenser and a dynamic microphone. Hence impulse responses are not directly comparable. " --- https://www.dpamicrophones.com/mic-university/10-statements-on-condenser-microphones-vs-dynamic

Does anyone make "condenser" phono cartridge?
 

RayDunzl

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Maybe my cheesy drawing above is somewhat in error, if the difference in the output waveform of pressure and velocity pickups vary not in shape but phase.

Hmmm...

Now I have something to think about...
 

Blumlein 88

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Condenser (capacitive) vs Dynamic (diaphragm and voice coil) Microphones exhibit a similar difference...

"The waveform of the output of a condenser microphone is directly related to the sound pressure of the sound wave. The waveform of the dynamic microphone is related to the velocity of the sound wave. When the pressure hits the peak, the speed of the air molecules is zero. At this point, the condenser signal is at max, and the dynamic signal is zero.

In general, there is a 90° difference between the signals from a condenser and a dynamic microphone. Hence impulse responses are not directly comparable. " --- https://www.dpamicrophones.com/mic-university/10-statements-on-condenser-microphones-vs-dynamic

Does anyone make "condenser" phono cartridge?
Stax made one way back when. And seems some Technics electret phono cartridges were around. I also seem to recall a buddy with many odd vintage audio bits of gear had one which might have been a Stanton.
 

Blumlein 88

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Yes, but transformations within the electronic domain (analog - digital - analog) have much lower loss then transformations between the electronic domain and other domains:
  • electronic - air pressure, e.g. microphones/speakers
  • electronic - mechanics, e.g. vinyl cutting stylus/playing stylus.
  • electronic - magnetics, e.g. tape heads
Not long ago @Blumlein 88 posted several pieces of music which were transformed 8 times from digital to analog and back to digital, and very few people could here the difference. This is not possible with analog tape, vinyl, or microphones and speakers.
I still have in mind doing the same with cassette tape for a comparison. 8 generations of cassette tape will be an obvious difference. The question is if enough will remain to recognize the music. :)
 

RayDunzl

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I still have in mind doing the same with cassette tape for a comparison. 8 generations of cassette tape will be an obvious difference. The question is if enough will remain to recognize the music.

I think it will take a long time to eliminate the music (though it may not be very musical).

Experiment:

Take a tune and amplify it (permit clipping) until there are only two levels remaining.

Basically, if the original sample was positive, the new sample = full scale positive.

When the original sample was negative, the new sample = full scale negative.

The only information remaining is "when" a zero crossing occurred.

There might be a zero value in the new wave, but I haven't found one yet.

1560560797745.png




Listen:

VOLUME WARNING - MAY BE VERY LOUD
VOLUME WARNING - MAY BE VERY LOUD
VOLUME WARNING - MAY BE VERY LOUD



Replacement file here that is not so loud... 30dB lower.


Original Spectrum of the whole tune:

1560562128688.png


1-bit Spectrum (graph scale changed on its own)

1560562194940.png
 
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Blumlein 88

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@RayDunzl
OOOOOOH!!!!!! Ray, that was damned loud when I played it. Please insert a warning to anyone going to listen.

Why don't you dump both versions into Deltawave and see what happens.

Also might try a low pass filter to see if it can bring the result closer to the original.
 

RayDunzl

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Blumlein 88

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BTW, Ray, are you going to patent this. I think this approach is the final step to win the loudness war. So you need to patent it, and sell it as a plug in for DAWs.

Now I took a file and did the same. Then switched it to 24 bit out of 32 bit float. This let me reduce volume by 6 db so it wasn't all clipped. It of course looks like variable width squarewaves or PWM. I then did a 1st order roll off starting at 40 hz. And you get a pretty good version of the original with of course a very rolled off response. Why are we doing this again?

On Deltawave well what was the null depth and the delta spectrum.
 

Wombat

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@RayDunzl
OOOOOOH!!!!!! Ray, that was damned loud when I played it. Please insert a warning to anyone going to listen.

Why don't you dump both versions into Deltawave and see what happens.

Also might try a low pass filter to see if it can bring the result closer to the original.


What, I can't hear you? o_O DR4 sounds good now. :facepalm:
 

RayDunzl

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Why are we doing this again?

As a response to multiple generations of cassette tape, and somebody wondering if there would be anything recognizable left after a few runs.

I think "yes".
 

RayDunzl

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SoundCloud's codec messes with my music!

No longer 1-bit.


No, this is all local files, so DeltaWave is showing 3 levels unexpectedly.

1560571116307.png
 
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