Not another debate thread - Just a question

famous beagle

famous beagle

Well-known member
First off, I prefer working with analog, just so everyone knows on which side of the fence I am. However, I'm confused about something, so I thought someone here may be able to clear it up.

Ok ... so ... from what I understand, magnetic tape basically (and I stress basically) works like this:

The tape is coated with metallic oxide particles.
A high-frequency signal (bias) energizes these particles (basically) and aids them in overcoming intertia
The incoming analog signal is converted to an electric one, which charges the oxide particles and arranges them in an order, which forms an "analogue" of the sound wave.
Upon playback, this analogue is then read by the playback head and sent to the speakers, where it's converted back to an analog signal.

Is that the gist?

Assuming it is---and please feel free to correct any major errors if I made them---here's my question:

Analogue is often referred to as "continuous" recording, whereas digital is "sampled." But ... there has to be a finite amount of oxide particles on the tape, right? So ... there can only be so many available to form the "analogue" of the sound.

So ... in a sense, isn't analogue recording essentially sampling the sound as well? I mean, I have no idea how many oxide particles are used to represent the signal at any given time (or space on the tape), but it's finite. And the less oxide you have on the tape, the less complete the signal would be, right? (Similar to a lower digital sampling rate)

Am I right in thinking this? Or am I way off?

Thanks for any input!
 
Steenamaroo said:
I can't answer, but I'm definitely interested. Looking forward to seeing some responses.
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Me to !! and actually the part about "So ... in a sense, isn't analogue recording essentially sampling the sound as well?" it seems to me that's what it could be called "a sample of the original sound" but just put on magnetic tape instead of a hard drive right ? ;)
 
Well...the particles don't "store" the audio....so it's not like if you have x-amount of particles, you can only store x-amount of audio.

The audio is converted to an electric signal which in turn is converted to a magnetic field that simply aligns particles in a various positions to create a magnetic footprint that is then read by the playback head as a magnetic field, and converted back to electronic signals, and finally audio/sound.

The magnetic field is not as series of "slices" (samples)....it's a continuous field. All the particles do is hold the field in its shape along the tape.
IOW...if you have a magnet, you have an entire field...but only one magnet to shape it. So it's not about the oxide particles individually "storing" audio info....they simply maintain the field's orientations/shape.
 
That makes sense to me but is not OP not asking what kinda size these particles are?

It's ridiculous but say they were 1mm in size for the sake of discussion, they'd do the same thing as recording digitally at a low sample rate, right?

Keep in mind I've no idea what I'm talking about. :p
 
miroslav said:
Well...the particles don't "store" the audio....so it's not like if you have x-amount of particles, you can only store x-amount of audio.

The audio is converted to an electric signal which in turn is converted to a magnetic field that simply aligns particles in a various positions to create a magnetic footprint that is then read by the playback head as a magnetic field, and converted back to electronic signals, and finally audio/sound.

The magnetic field is not as series of "slices" (samples)....it's a continuous field. All the particles do is hold the field in its shape along the tape.
IOW...if you have a magnet, you have an entire field...but only one magnet to shape it. So it's not about the oxide particles individually "storing" audio info....they simply maintain the field's orientations/shape.
Click to expand...

Yeah, I'm not saying they store the audio. I was trying to say that they align in a pattern that represents the magnetic field. But ... "they" are not infinite. They're particles, so there has to be a finite number of them, correct? And doesn't that mean that there's a limit as to how accurately they can represent the magnetic field (i.e., signal)?
 
I'm looking at it like this: If you were to make several batches of tape, each one with a reduced amount of iron oxide, what would you begin to hear/measure as you made identical recordings on the batches?

It seems logical that s/n would drop, which would correspond with bit-depth, no?

Also seems logical that distortion would increase, as the tape would probably saturate faster. Perhaps it would not be as linear in frequency response as a result. Not sure how that corresponds to digital.
 
famous beagle said:
But ... "they" are not infinite. They're particles, so there has to be a finite number of them, correct? And doesn't that mean that there's a limit as to how accurately they can represent the magnetic field (i.e., signal)?
Click to expand...

But again...you are seeing the particles as somehow key to how much audio is "stored"....but they have nothing to do with that.
IOW....if you "counted " particles per sq inch on various tape brands, it's not like they would all shoot for a spefic number in order to deliver a specific audio depth/quality....as in samples and bits.
The particles just shape the magnetic field. There are probably way more than needed on most oxide formulations to shape it....and the field is a continous thing, not slices/samples. Now the actuall strength of the field and what have you in the different oxide formulation can give you different flavors of sound....but AFA equating magnetic fields to sampling....it's not quite the same.
 
I guess whereas in digital, nyquist will cut off your spectrum lower and lower as sample rate decreases, tape would probably saturate faster as oxide decreased. You lose HF content and increase aliasing in the audible spectrum (in digital) vs lose s/n and increase distortion (with tape).

Just my guess...
 
miroslav said:
But again...you are seeing the particles as somehow key to how much audio is "stored"....but they have nothing to do with that.
IOW....if you "counted " particles per sq inch on various tape brands, it's not like they would all shoot for a spefic number in order to deliver a specific audio depth/quality....as in samples and bits.
The particles just shape the magnetic field. A few more or less will change the audio quality. There are probably way more than ]needed to shape it....and the field is a continous thing, not slices/samples.
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Ok, how about looking at it like this: You know the experiment where you put a bunch of metal filings on a plate and put a magnet beneath it? And the particles align to show the magnetic field?

Well ... the more filings you have on the plate, the more detailed the magnetic field will look, correct?

Is it not the same on tape?
 

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I'm sure Beck could give you a more lucid explination....I'm sorta dancing around it with two left feet. :)
 
famous beagle said:
Ok, how about looking at it like this: You know the experiment where you put a bunch of metal filings on a plate and put a magnet beneath it? And the particles align to show the magnetic field?

Well ... the more filings you have on the plate, the more detailed the magnetic field will look, correct?

Is it not the same on tape?
Click to expand...

That's what I kinda pictured. If you have six long filings you get a hexagon.
If you have a thousand, it's still not a circle, but it damn sure looks like one.
 
I don't know enough about it to say exactly what physical properties cause it - but typical analog tape machines have only slightly better high frequency response, and quite a bit less dynamic range compared to even CD quality digital audio.
 
miroslav said:
I'm sure Beck could give you a more lucid explination....I'm sorta dancing around it with two left feet. :)
Click to expand...

But ... so are you trying to say that I'm essentially wrong? That the number of oxide particles on the tape has nothing to do with how accurately it can represent the signal?
 
famous beagle said:
Is it not the same on tape?
Click to expand...

It's not the *number of particles* per audio signal...it's their alignment/shaping of the field. I'm sure you need a certain amount to make it viable for recording....but adding a few more or having a few less will not change how the magnetic field is charged/shaped by the electronic signals, which happens BEFORE it hits the oxide.
So it's NOT like the particles are sampling slices of audio or even dictating how much....they are just "remembering" the shape/charge/direction of the magnetic field along the tape. I'm pretty sure it would be the same magnetic shape/charge/direction regardless of the amount of oxide...though like I said, there's probably more than enough on the tape.
IOW...if it aligns N-to-S...it would do so with 5 or 10 particles...and the audio "message" is in that.

Saturation is just a point where there is so much audio electronic signal that the magnetic field is stronger than the oxide particles can hold....but not necessarily because there are not enough particles. It's just the type of oxide.
 
miroslav said:
It's not the *number of particles* per audio signal...it's their alignment/shaping of the field. I'm sure you need a certain amount to make it viable for recording....but adding a few more or having a few less will not change how the magnetic field is charged/shaped by the electronic signals, which happens BEFORE it hits the oxide.
So it's NOT like the particles are sampling slices of audio or even dictating how much....they are just "remembering" the shape/charge/direction of the magnetic field along the tape. I'm pretty sure it would be the same magnetic shape/charge/direction regardless of the amount of oxide...though like I said, there's probably more than enough on the tape.
IOW...if it aligns N-to-S...it would do so with 5 or 10 particles...and the audio "message" is in that.
Click to expand...

Hmmm ... I still can't say I understand fully. But thanks for trying to explain it.
 
Well...if you look at the picture you provided....if there were less particles on the table...they would STILL align in the same manner...and that is where the audio "message" is derived from, the alignment, and not specifically in the pure number of particles.
 
miroslav said:
Well...if you look at the picture you provided....if there were less particles on the table...they would STILL align in the same manner...and that is where the audio "message" is derived from, the alignment, and not specifically in the pure number of particles.
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That makes sense, but what about what Steen said earlier:
"That's what I kinda pictured. If you have six long filings you get a hexagon.
If you have a thousand, it's still not a circle, but it damn sure looks like one."

I think the attached image is what got me started thinking about all this in the first place.

And why then does running a tape at higher speed increase fidelity if not for the fact that more oxide is being used to represent the same signal?
 

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famous beagle said:
That makes sense, but what about what Steen said earlier:
"That's what I kinda pictured. If you have six long filings you get a hexagon.
If you have a thousand, it's still not a circle, but it damn sure looks like one."
Click to expand...

The hole in that idea is that particles will always be the same size, but it's still an interesting thought.
I suppose we (I) would have to understand how they are arranged and what exactly that represents.

I think those from the digital age have a tendency to picture digital waveforms which would certainly suffer as a result of being represented by fewer samples.
The difference there is that the samples are longer, where as particles on tape are just spaced out.
Maybe it doesn't make any difference?
 
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