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Analog audio

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Title: Analog audio  
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Subject: Analog signal, Broadcasting, Digital recording
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Analog audio

Analog (or analogue) recording (Greek, ana is "according to" and logos "relationship") is a technique used for the recording of analog signals which among many possibilities include audio frequency, analog audio and analog video information for later playback.

Analog recording methods store signals as a continual wave in or on the media. The wave might be stored as a physical texture on a phonograph record, or a fluctuation in the field strength of a magnetic recording. This is different from digital recording of which among many possibilities include digital audio and digital video, which digital signals are represented as data or discrete numbers.

The Phonograph

The Phonograph was the first machine used to capture analog sound, and was invented by the well-known inventor Thomas Edison in 1877. Edison incorporated various elements into his Phonograph that would become staples that can be found in recording devices to this day.[1]


For a sound to be recorded by the Phonograph, it has to go through three distinct steps. First, the sound enters a cone-shaped component of the device, called the microphone diaphragm. That sound causes the microphone diaphragm, which is connected to a small metal needle, to vibrate. The needle then vibrates in the same way, causing its sharp tip to etch a distinctive groove into a cylinder, which was made out of tinfoil.


In order to playback the sound recorded on one of the tinfoil cylinders, the recording process is essentially reversed. As the cylinder spins, the needle follows the groove created by the previous recording session. This causes the needle to vibrate, and then the diaphragm. This vibration comes out of the diaphragm, which is now functioning as a sort of sound amplification device, much like the bell on any wind instrument. The result is an audible reproduction of the originally recorded sound.

Problems with the Phonograph

Edison’s Phonograph was the first of its kind, meaning that it would have been an impressive piece of technology to anyone living at the time. This does not mean that it did not have its drawbacks though.

The biggest of these, and the one that ended up being fixed first, came from the physical contact between the Phonograph’s needle, and the tinfoil diaphragm. Because the needle had to continually make contact with the groove in the diaphragm every time the recording was played, the groove would wear down. This meant that every single time a recording was played, it was one step closer to being gone forever.[2] Another problem with the Phonograph was the permanence of its recordings. Unlike music today, which can be edited endlessly, the music captured by Phonograph machines were single-take, live recordings.[2]

The last problem with the Phonograph had to do with fidelity. Fidelity is the similarity/difference between the original recorded sound, and that same sound after it has been reproduced by a playback device, in this case the Phonograph.[2] As can be expected from such an early audio recording machine, the fidelity of Edison’s Phonograph was extremely low. This lack of sound quality is why the Phonograph was originally used to record speeches, meetings, and telephone calls, rather than music.[2]

The Gramophone

Fans of modern record players are already familiar with one very early improvement on Edison’s Phonograph, which was called the Gramophone. Inventor Emil Berliner created the device in 1887, only ten years after Edison’s original device.[3]

Advantages of the Gramophone

Berliner’s main improvement to the Phonograph had to do with the component of the device that actually held the recorded information. The previously used tinfoil cylinders were awkwardly shaped, making them hard to store.[2] They could also not be reproduced economically, which was another reason why they were not seen as a viable option for recorded music.[2] Berliner realized these disadvantages, and set out to create a better version of the tinfoil cylinder. What he came up with was not a cylinder at all, but was rather a flat circular disc much like modern vinyl records. These discs could not only be easily stacked and stored for safe-keeping, but were also comparatively easy to reproduce. This quality allowed for the mass production of recorded discs, which was the first step towards commercially recorded music.[2]

Problems with the Gramophone

Unfortunately, though the Gramophone was a large step up from the Phonograph commercially, it still had many of the same problems.[2] The mass production possibilities created by Berliner’s flat discs got companies thinking about recording music, but since nothing had been done to address the low fidelity issue, the industry had yet to really take off. The problems with finality and breakdown of recordings started by the Phonograph were equally as prominent with the Gramophone.[2]

The Telegraphone

The next great advancement in analog sound recording came in the form of the Telegraphone, which was created by Danish inventor Valdemar Poulsen between 1898 and 1900. This machine was vastly different than the Gramophone or its predecessor the Phonograph, in that instead of recording sound mechanically, it recorded using a process called electromagnetism.[2][4][5]

Poulsen was able to transmit an electrical signal, much like the one that would broadcast over the radio or a telephone, and then capture it on a magnetizable element, in this case a length of steel wire, which was wrapped around a bass drum.[2]

Problems with the Telegraphone

Poulsen’s Telegraphone was not without its share of problems though. First, the reels of steel wire were extremely heavy, weighing in at around 40 pounds each. Also, it was very expensive to use steel to record on, due to its relative scarcity during the era. It would cost 1 Dollar for every minute of recording, which translates to a hefty expense when the multiple redos that would have had to been done to capture the “best” take of a performance is taken into consideration.[2]

Next, as can be expected, the use of steel wire was dangerous. If you can imagine bandsaw, with a length of razor-sharp steel wire moving back and forth at a rate of 1.5 meters per second, then you have successfully realized the inherent danger of these machines.[2]

Like the recording devices that came before it, the Telegraphone recordings were nearly impossible to edit. Rather than cutting and splicing together multiple takes, as could easily be done with scissors or a computer in future recording devices, this machine required both a welding torch and a soldering tool to get the job done.[2]

The Magnetophon

But in 1935, an inventor named Fritz Pfleumer took the electromagnetic recording idea and took it to the next level.[2] Rather than using heavy, expensive, and dangerous steel wire like Poulsen, Fritz Pfleumer realized that he could coat normal strips of paper with tiny particles of iron. The iron would allow the paper to be magnetized in the same way as the steel wire, but would eliminate most of its shortcomings.[2]


The way things were recorded with the Magnetophon was nearly identical to the process used in the Telegraphone. An inscriber, called the recording head, passes over the electromagnetic paper strip, creating patterns of varying magnetic polarity within it, which can later be played back.


The playback is achieved using a reversal of the recording process.[2] The pre-magnetized paper, which had come to be known as tape, passed over a coil, creating changes in magnetic flux. These changes were translated into an electric current, which when amplified produced a replica of the previously recorded sounds.[2]

Advantages of the Magnetophon

There were many advantages of tape recording, but the most important was that it led to the development of multitracking. Multitracking occurs when multiple takes of a performance, which were recorded at separate times, are brought together to play simultaneously. This is the method all recording studios use to this day, in order to record all of the separate instruments of a song, and get the best possible takes from all of the musicians.[2]

Another huge advantage of the electromagnetic recording process in general was the fact that there was no physical contact between the recording/playback head and the tape itself. This alleviated the problem of durability found in both the Gramophone and Phonograph. Rather than breaking down gradually with every play, the life of taped recordings were limited only by the life of the tape substrate itself, which is a much longer time frame.[2]

A reel of tape could also hold far more recorded information than previous mediums. For instance, Emil Berliner’s discs held only a few minutes of recording, meaning that each disc usually contained a single song, or multiple short clips. Pfleumer’s tape reels, on the other hand, could hold up to thirty minutes of sound. This ability is what eventually led to the concept of a music “album”, or collection of multiple songs.[2]

Problems with the Magnetophon

The original Magnetophon had its share of setbacks as well. Namely, the problem of low fidelity found in previous devices had yet to be solved. Though audiences and inventors had not yet experienced what high fidelity recording would even sound like, they knew that the sound they were hearing from recordings needed to be improved before any kind of recorded music industry could be expected.[2]

A.C. bias

The answer to the reoccurring problem of low fidelity turned out to be the simple fact that inventors were not using all the right electronic currents.[2] While all forms of electromagnetically recorded music were using something called DC current, they had yet to try another form of electric current, called AC.[2] It turns out that AC current contains higher frequencies than its DC counterpart, and that those higher frequencies were what had been missing in electromagnetic recording thus far. Those high frequencies “shake-up” the magnetic particles on the tape in just the right way, creating the first high fidelity sound recordings.[2] Interestingly, this process known as AC Bias was discovered in 1940 by two inventors living in different parts of the world, who were both unaware of the other’s discovery.[2]

See also


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