Analog Tape Theory

`similar' or `in direct relation with'

Magnetic Remanence

In direct relation with and in proportion to the electrical waveform signal given at its input.

Good quality tape and Special compensation circuitry

CAPSTAN and the PINCH ROLLERS

Shaft, usually made of nylon, of a very finely tuned, Constant motor called the CAPSTAN MOTOR

CAPSTAN MOTOR

Squeezes the tape against the capstan, to draw the tape along at an exact, selectable speed.

ERASE HEAD, RECORD HEAD, PLAYBACK HEAD

Erase Head.

Wipes out any previous signal on the tape which passes it, making any section of the tape reusable.

Converts the stored magnetic energy back into electrical impulses

Very low level and must be amplified many times before we can hear it

Transducer which converts electrical energy impulses into variations of a magnetic energy field.

WOW and FLUTTER.

WOWING

Motor failures or worn components (such as bearings) or even dirt on the transport.

Poor cleanliness or care of the equipment

The periodic raising and lowering of the pitch of the program material.

Electro- Magnet

Flow of magnetism (FLUX) from one pole to the next.

Thin layer of Mylar or similar material coated with iron oxide.

Charge on the oxide, which polarizes the oxide particles and effectively "captures" the signal.

Thin plastic ribbon with randomly oriented microscopic magnetic particles glued to the surface.

Polarization (not the physical orientation) of the tiny particles so that they align their magnetic domains with the imposed field

The more particles align their orientations with the field, until all of the particles are magnetized.

An electrical signal is produced.

Magnetic field which can be used to create a pattern of magnetization in the tiny magnetic particles of the tape.

It will not relax back to zero magnetization when the imposed magnetizing field is removed.

Hysteresis loop

It takes some energy to turn them back again

Magnetic "memory"

Bias frequency

High Frequency biasing signal

“Active”

Sensitive to their previous magnetic history (hysteresis)

Dither

A High frequency signal, typically between 40 kHz and 150 kHz, applied to the record head along with the audio signal when an audio track is placed into record.

When recording to analog tape.

The magnetic field created by the record head is not strong enough to polarize the magnetic oxide particles on the tape., Thus, a distortion of the original audio signal is introduced.

The bias current is Applied to break down this resistance to polarization., The audio signal can then be recorded more accurately without the effects of low level distortion.

Frequency response, Distortion characteristics of an analog recording

Little more high frequency

Transferring program information onto tape is measured as a quantity of lines of flux or fluxivity once on the tape.

The further away you are from the noise floor but the closer you are to the point of distortion

185 nWb/m

250 nWb/m

320 nWb/m

370 nWb/m

520 nWb/m

Physical adjustment that adjusts the angle of the head.

90 degree

Playback test tones previously recorded on the head, Check the phase alignment with a phase meter between outside tracks (top and bottom of the head)

Reading tones from the playback head while recording onto the record head, Therefore we must make sure the electronic alignment is right for the repro head first., A test tape (MRL) must be loaded onto the machine.

“Rule” for Playback Alignment