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Physics 1251
The Science and Technology
of Musical Sound
Unit 4
Session 38 MWF
Analog Recording and
Playback
Physics 1251
Unit 4 Session 38
Analog Recording
Who is Robert Moog and why is he
important?
Robert Moog (rhymes with vogue)
invented the Moog Synthesizer, a
pioneering instrument in the development
of the synthesizer.
Physics 1251
Unit 4 Session 38
Analog Recording
1′ Lecture:
•
•
•
•
•
Recording requires a transducer, such as a
microphone, to produce an electrical signal.
Common types of microphones are (1) condenser;
(2) magnetic; (3) dynamic; (4) ribbon; (5) piezoelectric;
(6) carbon.
Recording also requires amplification as well as a
storage medium.
Analog recording media include vinyl record, magnetic
tape, magnetic disk and optical film.
Playback uses physical principles in which mechanical
oscillations, magnetic domains and optical density
variations produce electrical signals that are analogous
to the recorded sound.
Physics 1251
Unit 4 Session 38
Analog Recording
80/20An
electric guitar uses a magnetic pickup
that produces an electrical signal by a
time-varying magnetic field.
Steel Guitar String
N
S
Pickup
Physics 1251
Unit 4 Session 38
Analog Recording
80/20The
Faraday Effect : a magnetic field that
varies in time produces a voltage and
current in a coil.
Current
N
S
Physics 1251
Unit 4 Session 38
Analog Recording
80/20A
Condenser Microphone uses electric
induction to produce an electrical signal.
Charge = V (εo S/x)
Voltage V
+
+
+
+
Current I
+
+
Physics 1251
Unit 4 Session 38
Analog Recording
80/20Magnetic
Microphone: a small magnet,
attached to a moving diaphragm induces
a voltage and current in a coil.
Current I
Voltage V
Physics 1251
Unit 4 Session 38
Analog Recording
80/20Dynamic
Microphone: a diaphragm moves
a small coil in a magnetic field inducing a
voltage and current.
Current I
N
S
N
Voltage V
Physics 1251
Unit 4 Session 38
Analog Recording
80/20A
Ribbon Microphone uses a light weight
ribbon of metal moving in a magnetic field
to produce electrical signals.
Current I
N
S
Voltage V
Physics 1251
Unit 4 Session 38
Analog Recording
80/20Piezoelectric
Microphone: a thin crystal is
bent which produces a small voltage.
+
+
Voltage V
+
Physics 1251
Unit 4 Session 38
Analog Recording
80/20Carbon
Microphone: a diaphragm
compresses a sealed container of carbon
granules, changing its resistance.
Current I
I = V/R
Voltage V
Physics 1251
Unit 4 Session 38
Analog Recording
Microphones:
•
Electrostatic—Induction
• Condenser
•
Magnetic—Faraday Effect
• Magnetic
• Dynamic
• Ribbon
•
•
Piezoelectric—Piezoelectric Effect
Carbon—Ohm’s Law
Physics 1251
Unit 4 Session 38
Analog Recording
80/20A
Vacuum Tube is an electronic device
that amplifies electrical signals by
permitting a small voltage to modulate a
much larger current.
Vin
Cathode
Grid
Plate
Vout
Gain = Vout /Vin
Physics 1251
Unit 4 Session 38
Analog Recording
Amplification:
Gain G = Vout / Vin
Vout
Vout = G Vin
Vin
Physics 1251
Unit 4 Session 38
Analog Recording
80/20A
Field Effect Transistor (FET) is a solid
state electronic device that permits
amplification of electrical signals.
Gate
Source
Silicon
Drain
Silicon
Dioxide
Physics 1251
Unit 4 Session 38
Analog Recording
Analog Recording Media:
•
Mechanical
• Edison’s Phonograph
• Vinyl LP Records
•
Magnetic
• Magnetic Tape
• Magnetic Disk
•
Optical
• Audio Track on motion picture film
Physics 1251
Unit 4 Session 38
Analog Recording
Mechanical:
•
Edison’s Phonograph
Physics 1251
Unit 4 Session 38
Analog Recording
Mechanical:
•
•
Edison’s Phonograph
Vinyl LP Records
Physics 1251
Unit 4 Session 38
Analog Recording
Analog Recording Media:
•
Magnetic
• Magnetic Tape
• Magnetic Disk
Physics 1251
Unit 4 Session 38
Analog Recording
Analog Recording Media:
•
Magnetic
• Magnetic Tape
• Magnetic Disk
Ferro-metal
Oxide
Tracks
Physics 1251
Unit 4 Session 38
Analog Recording
Analog Recording Media:
•
Optical
• Audio Track on motion picture film
Stereo Audio Tracks
Physics 1251
Unit 4 Session 38
Analog Recording
Analog Recording Media:
•
Optical
• Audio Track on motion picture film
Stereo Audio Tracks
Physics 1251
Summary:
•
•
•
•
Unit 4 Session 38
Analog Recording
Common types of microphones are (1) condenser;
(2) magnetic; (3) dynamic; (4) ribbon;
(5) piezoelectric; (6) carbon.
Vacuum tubes and transistors provide amplification
by permitting the input to modulate a larger output
current and voltage.
Analog recording media include mechanical,
magnetic and optical storage.
Playback uses physical principles in which
mechanical oscillations, magnetic domains and
optical density variations produce electrical signals
that are analogous to the recorded sound.