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Amplifiers (Related concepts (Compression (Reduces the volume of loud…
Amplifiers
Related concepts
Compression
Reduces the volume of loud sounds
Amplifies quiet sounds
Compression of the dynamic range
Audio spectrum
Wave interference
Electrical impedance
Fender tweed amps
Transducer
Polarity
Mains power
Preamp
Shapes the tone
Transform the input signal to a manageable level
Passes the signal through gain stages (one or more)
Vacuum tubes
Transistors
Reduces impedance
Noise filtering circuitry
Volume control and equalizer
Negative feedback
Taps a portion of the power amp output
Inverts the polarity and feeds it back to the power amp
Inverted signal has a prominent midrange
Cancels-out the midrange in the poweramp input (destructive interference)
Presence control
Effects loop
Compression is a byproduct of distortion
Negatively affects some effects like delay, reverb, and tremolo
Effects loop sits between the preamp and the poweramp
Wah-wahs and gain boosts before the preamp
Four cable method
Poweramp
Drives the speaker
Boost the electrical signal to a higher voltage
Uses AC mains power
Larger vacuum tube and transistor systems than the preamp
Speaker
Electronic transducer
Size
Professional amps - 10" - 12" diameter
Practice amps - 4" - 8" diameter
Characteristics
Larger cabinets
Full-bodied sound
Smaller cabinets
Midrange heavy
Construction
Open back
Limits bass
Higher sound dispersion
Closed-back
Higher bass
Directional sound
Master volume
Overdrive creates excessive volume
A second volume control between the preamp and the poweramp control the overall output
First volume control (gain) overdrives the preamp
Volume control is place before the preamp if no gain control is present
Layout
Amp stack
Amplifier head and speaker cabinet
Full stack (two cabinets) and half stack (one cabinet)
Combo amplifiers
Multi-channel amps
Two preamp circuits with two presets
Channels can be switched using a footswitch