Transcript Yuriy_Kharin_Matt_Andrews_POSTER1x

Vacuum Tube Audio Amplifier
Matt Andrews, Yuriy Kharin
Adviser: Dr. Michael J. Carter
Why Vacuum Tubes?
 Very linear even when driven in saturation
region(smooth clipping)
 Can be used in very high voltage circuits
 Able to withstand over-voltage and overheating for
minutes where transistors would blow in milliseconds
 Believed to have a more natural, fuller, and warmer
sound reproduction.
 Even order harmonics which is less offensive to human
hearing
Objectives:
 To design and build an audio
amplifier using vacuum tubes
 To design and build a high wattage
power supply
Design of the amplifier:
 Input Stage: Simple single tube stage designed for high
input resistance and linearity. Global negative
feedback is applied here from the output.
 Phase Splitter: Uses matched resistors at the plate and
cathode to produce two equal signals of opposite
phase. Critical for push pull design.
 Driver Stage: Takes the signal and amplifies it further.
 Output Stage: High current gain and implements an
output transformer to match the high output
impedance of the amplifier to the eight ohm load.
Employs potentiometer networks to ensure equal grid
signal amplitudes and operating currents.
 Global Negative Feedback: Reduces total harmonic
distortion
How it works:
 4 Main components: Filament,
Cathode, Anode, and the Grid
 When filament is heated,
cathode releases negatively
charged electrons that get
attracted to positively charged
Anode
 The grid is located between the
cathode and the anode and
controls the flow of electrons
just like the base and the gate
in BJTs and MOSFETS
Design of the power supply:
 Power Transformer: Steps up the voltage coming out of the outlet
 Rectifier: Makes the AC signal all positive
 Ripple smoothing: Inductor and 2 capacitors form a Pi filter which
turns the rectified voltage into DC
 Voltage Regulation: Maintains constant voltage level of 360V
regardless of the amount of current drawn
Final Product:
 72 watt power supply.
 25 watt Class AB1 push pull audio
amplifier.
 Two chassis mono-block design.
 Plays music from a laptop or a
small signal source clearly into an
8 ohm speaker.
Special thanks to Adam Perkins, Mike Andrews, Lincoln Lavoie, and Tom Merrick