Analog Tape
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Analog Tape
Analog Tape uses the concept of Magnetic Recording, it was only developed commercially for Recording Studio's after WWII thanks to progress by German engineers during the war. Earlier steel tape machines were used in the BBC and other radio stations in the 30's but were fragile and not widespread.
Analog Tape is a Magnet made from a polyester base strip "sprinklked" with ferric oxide, which is then "glazed". Tape speed is held constant by the Capstan. Most tape machines have 3 heads.
Tape Heads
The Erase Head which comes first emits a high amplitude, high frequency AC Signal that removes any previously recorded material or magnetization of any sort from the tape..The high amplitude "zap" of AC causes the particles on the tape to reorient themselves in a random fashion, thereby erasing program material.
The Record Head is responsible for taking signal current, music coming in to the record amplifier, and converting it into electro magnetic current or lines of flux. Magnetic lines of flux are produced through use of a simple coil wrapped soft metal electro magnet. The record head also doubles as the syncronus playback head, or sync head. Allowing the user to monitor playback and record at the same instant. This facilitates overdubbing and punching.
The playback head reads the magnetic information on the tape. Through a process directly inverse of the record head, the playback head gaps induce current to be sent back into the playback amplifier, which in turn plays back the program material.
The record head also uses A.C. Bias to minimize the "flipping" from positive to negative tendency of the magnetic tape, this is something that one must take care to adjust properly in order to have an accurate recording. The technical term for this "flipping" phenomenon is hysteresis, which is overcome by the AC Bias, AC bias is a powerful signal in the ultra sonic range, usually around 150khz this signal excites the particles on the tape thereby causing them to be more coercive and malleable, improving the linearity of the process of conversion to and storage of magnetic information. The principle of hysteresis states that the particles do not want to reorient, they want to stay at rest. This resistance to motion causes the magnetism to align the particles on the tape in a distorted fashion. The AC Bias overcomes this resistance and eases the orientation process. The non linearity of analog recording is also compensated for by inserting an EQ curve in the signal path of the playback circuit.
Tape Types
The power emitted by the head responsible for transferring program information on to tape is measured as a quantity of lines of flux or fluxivity once on the tape this is measured in NanoWebers per meter. Analog tape is currently only being produced by one or two companies so the type of tape is now less crucial. Some companies that have produced tape are Quantegy and Ampex. When picking an operating level for tape, the general rule is that the higher the operating level the further away you are from the noise floor but the closer you are to the point of distortion.
Note: Always store tape "tails out" to avoid a type of "sonic foreshadowing as a result of print through, if you store it tails out any print through will be delayed rather than show up a few ms before the audio.
Alignment tones
Alignment tones are printed at 1kHz, 10kHz, 15kHz, and 100Hz at levels of 0 VU on the tape machines meters. Printing tones is required to bring out operating reference level with us from session to session, tape machine to tape machine. It is the "benchmark" of our project operating level that enables us to exactly replicate the setup in any analog recorder we may be working on, at any time, in any studio. From these tones we can adjust level, EQ, and Azimuth. A record pad is also included allowing one to set the record amplifiers/alighment on the exact tape we will be recording on.
Tape Machines
Most popular among Professional studio's is probably the Studer 24 track 2" tape machine, along with 2 track 1/2" Studer tape machine (the 2 track is primarily used for bouncing down final mixes or mastering, due to its higher quality).
Other brand's include: Ampex Tascam Teac Studer
