The Science of Pre-Amps

The Science of Pre-Amps

FOLLOW THE SIGNAL

● Source – voice, instrument, sound, noise, etc…

● Air – propogates sound wave (acoustical energy)

● Microphone (Sensor) - converts acoustic to electrical energy

● Pre-Amp – first modification (amplification) of signal

●● Cable – correctly connects all components of system

●● Amp– second modification of signal

●● Speaker Output - signal transformed from electrical energy back into acoustic energy

●● Air - propagates acoustic/sound wave

●● Ears - Receive Signal

THE SCIENCE OF

PRE-AMPS

● What does a Pre-amp do?

○>Amplifies voltage from mic level to line level

■ About .002 V to 1.2 V (increases about 600 times)

● What is Mic Level?

○ >It is the voltage level created in the mic capsule when it converts acoustic energy into electricity.

● What is Line Level?

○>Is the voltage level necessary for a signal to travel through the rest of the system optimally & without

degradation.

***Mic Level to Line Level Signal Explained (to 1:08) https://youtu.be/uvuo1VAKGnk?t=71

​>the rest of the system depends upon the pre-amp to create the correct voltage level (line level)

​In our studios and classroom...
-Where are some audio preamps located?
-Does every microphone need to be plugged into a preamp?
-By adjusting the "Gain Knob", how are you changing the audio signal?

PRE-AMP

● How does a Pre-amp do this?

○EMI (Electromagnetic Induction)

■ >magnets pushing electrons through a conductor, or moving electrons in a conductor
creates a magnetic field.
.
-we will be learning much more about this later!! Yay!

○ PhET demo?

○ >intro new term… transformer:
*Steps up voltages...
-increasing output level of microphones to line level

TRANSFORMERS

No…
Not that kind of transformer!!!

These kinds of transformers!!!

A TRANSFORMER,

in the Audio Pre-Amp World,
Consists of…

● 1. Donut -Shaped Magnet

● 2. Copper windings on 2 sides of magnet

● >There are variables in transformer

○ Strength & Size of magnet
○ # of primary windings
○ # of secondary windings

YOU CAN’T GET SOMETHING FOR

NOTHING, SO…

▪ Incoming mic level….

✔ .002 Volts

▪ Out going line level….

✔ 1.2 Volts

▪ So, it’s…. .002 Volts (mic level) + __?_= 1.2 Volts (line level)

?= 1.198 Volts

*Huh? Where did “?” come from?

…..I’ve got a tip for you…..

Plug it into the wall…duh!

✔ 120 V @ 60 Hz (remember, standard wall outlets are 120 Volts)

TYPES OF PRE-AMPS

● Solid State

●

● Vacuum Tube

SOLID STATE PRE-AMP

● Electronic circuitry – Transistors, resistors, etc...

○ >More reliable (no more burned out tubes)

○>More durable

>○>Cheaper (purchase price and maintenance)

○ >“Clean & Crisp” sound

VACUUM TUBE PRE-AMP

• Adds Harmonic overtones

•
>Adds Harmonic overtones

>“Warmer & Richer” sound

TYPES OF PRE-AMPS

Blue line – solid state

Black line – vacuum tube

​LLine level

REVIEW – BIG IDEAS OF

PRE-AMPS

● **Amplifies voltage of signalfrom Mic level to Line Level (600 times)

.002 volts to 1.2 volts

● **You can’t get something for nothing

○ Need wall power to get amplification of mic level to line level

**2 Types of Pre-Amps:

1. vacuum tube

2. solid state

Multiple Select

What is the function of a Pre-Amp in the process of sound amplification?

• Converts acoustic to electrical energy

• Amplifies voltage from mic level to line level

• Transforms signal back into acoustic energy

The Science of Sound Amplification

Line Level is the voltage level of a signal necessary to travel through the system without degradation. Signal degradation refers to the loss of quality or strength of the signal. This is achieved through electromagnetic induction, where magnets push electrons through a conductor, creating a magnet. Transformers play a crucial role in converting mic level signals to line level signals. They consist of a donut-shaped magnet and a coil of insulated wire.

Multiple Choice

What is the purpose of Line Level in signal transmission?

• To convert acoustic energy to electrical energy

• the voltage level necessary for a signal to travel through the rest of the system optimally

• To create a magnet through electromagnetic induction

Multiple Choice

What type of pre-amp is more reliable, durable, cheaper, and provides clean & crisp sound?

• Solid State

• Vacuum Tube

• Transistors

• Resistors

Solid State

Solid State pre-amps are more reliable, durable, and cheaper compared to vacuum tube pre-amps. They provide clean & crisp sound without the need for warm-up time. Solid State pre-amps use transistors instead of vacuum tubes, making them more efficient and less prone to failure. They are widely used in modern audio equipment.