3.3 Tape Delay

Tape Delay

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  • The peak level will illuminate if the signal clips or distorts and the VU meter shows the input level in volume units.
  • The mic/instrument volume is the gain. This can be decreased to avoid clipping. It can be turned up to obtain a better signal to noise ratio.
  • The instrument volume is for a low impedance instrument such as guitar.
  • The mode selector is used to select different taps / patterns / rhythms / types of delay / number or volume of repeats / combinations of playback heads.
  • The bass and treble controls are used to modify the tone of the delay (not the dry signal). It is a shelving filter that adjusts the levels of low and high frequencies.
  • The reverb/echo volume is the wet/dry effect mix. “Straight” gives no echo at all. This is the gain, and has a spring reverb unit.
  • Repeat rate is the delay time / the amount of time between each repeat.
  • Intensity is the feedback amount/number of repeats. This is the gain.
  • The power switch should be used so that the unit should be switched off when not in use to preserve the life of the tape.
  • Echo normal or footswitch works as a bypass (to switch off the machine).
  • HML gives different output levels/volumes so that the unit can match the different signal levels required by different studio equipment.

3.3 Vinyl and Records

Vinyl Records

  • Before the invention of tapes, compact discs and MP3 players, people listened to recorded music on record players.
  • With no fast forward or rewind controls, you chose an album and enjoyed about 25 minutes of music by one artist before flipping it over for more or putting another record on the turntable.

 Producing a Vinyl Record

  • A master recording is made, usually in a studio where engineers perfect the recorded sound.
  • Then an object called a lacquer is placed on a record-cutting machine, and as it rotates, electric signals from the master recording travel to a cutting head, which holds a stylus, or needle.
  • The needle etches a groove in the lacquer that spirals to the centre of the circular disc. The imprinted lacquer is then sent for mass production.
  • A metal master is produce that is an inverse copy of the final record. This is made into a stamper.
  • The stamper is placed in a hydraulic press, and vinyl is sandwiched in between.
  • Steam from the press softens the plastic as the stampers push an impression of the master recording onto it.

 

What is a Record?

  • The sound is stored on a single spiral groove. This groove stores a form of the waveform. Each side of the groove has a separate signal for stereo.
  • The outer ¼ inch is the lead in so the stylus can lowered onto the recording without damaging the recording.
  • Some records featured a lock groove which stopped the tone arm from going onto the centre of the record. Some bands recorded continuous music in this.
  • Records were and in some cases still are released in 7/10/12 inch sizes, with a speed / RPM of 33 1/3 /45/78

 

The Physics of Records

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The Record Player

  • The turntable is the circular plate on which the record sits.
    • A rod positioned in the center holds the record (which has a hole in its center) in place.
    • The metal turntable is covered in rubber or plastic, which protects the record from being scratched. The turntable rotates or spins with the help of either a belt drive or direct drive system.
  • The stylus, or needle, is the smallest and perhaps the most important component of the record player.
    • It is made from a diamond or other hard material, shaped like a cone and suspended by a flexible strip of metal.
    • The pointed end is the only piece that touches the top of the record and it rides around the spiraling grooves of the disk, picking up the vibrations which are ultimately turned back into sound.
  • The stylus sits at one end of the tone arm, which is mounted to the side of the turntable and sits parallel to the record.
    • With the needle or stylus placed in the outermost groove of the record, the tone arm follows the groove as it spirals inward, traveling across the record in an arc as the record spins under it
    • As this happens, the vibrations travel along a flexible metal strip and wires housed in the tone arm to the cartridge in the end of the tone arm.
  • The cartridge receives the vibrations, converted to electrical signals through a coil in a magnetic field.
  • The electric signals are carried along wires to the amplifier which enhances the power of the signal.
  • Finally, the signals are converted back to sounds that come out through the speakers.
  • Initially, recorded sounds were in mono, meaning all of the sound signals are combined and come through one speaker or channel.
  • The introduction of stereo sound systems in 1958 allowed for a richer, more lifelike sound as two sets of sound waves were recorded.

 

Record Resurgence

  • Many music lovers just prefer the sound of a vinyl record.
  • They argue that, despite the occasional extraneous noises on a record from dust or a scratch, vinyl has a deeper, richer sound than a digital version, which can feel too perfect.
  • They also enjoy other aspects of records, such as liner notes, photos, posters and other album extras.

 

Drawbacks of Vinyl

  • Record players need a flat surface and are prone to feedback. Sound quality deteriorates towards the centre of the record. This is because records have a constant rotation speed which gives varying amounts of vinyl per second travelling under the stylus.
  • Low frequencies are reduced on the record to reduce wide stylus movement. Record player amplifiers apply an EQ on playback to return the low frequencies to their correct level.
  • Records are prone to scratching and dust. This causes crackle, hiss and jumps on playback.
  • Due to the material, vinyl often needs dusting with a special duster to avoid a static charge building up which attracts dust. The record sleeve is made of polythene and helps reduce the charge.
  • Records can warp when exposed to heat, which causes fluctuations in pitch like wow and flutter.
  • Due to the nature of a record player, they are prone to rumble at less than 30Hz.