Basic Electronics Flashcards
How many paths for current flow are there in a Series Circuit?
1 path
Ohm’s Law
The mathematical relationship between voltage, current, and resistance
Short circuit
An incorrect path; 2 points connected together that shouldn’t be, usually resulting in excessive current flow
Voltage
A force that pushes electrons to move; electrical pressure that pushes electrons through wire; difference in charge between two points
What is the letter and measurement of Voltage?
E; volts
How to find the total sum of Resistance in a Parallel Circuit if the resistance is the SAME in each branch?
R(t)=R/# of branches
In a Parallel Circuit, is the total resistance more or less than the lowest branch’s resistance?
Less
What determines the South/North polarity of the magnetic field?
Direction of the flow of voltage current
Is Conventional Current Flow from + to - , or - to +?
+ to -
Is Electron Flow from + to - , or - to +?
- to +
What is the letter and measurement of Current?
I; amps (amperes)
What is Current directly proportional to ?
Voltage (E)
What is Current INVERSELY proportional to?
Resistance (R)
What is the letter/symbol and measurement of Resistance?
R; ohms Ω
How is electricity used in audio?
Sound is converted into a form of electricity that can then be amplified, recorded, processed and manipulated by other electrical components and circuits, then this electricity can be sent back out to create sound waves
What is electricity?
Flow of electrons through an electrical conductor
How do electrons flow?
They jump from atom to atom
What are examples of good conductors?
Most metals; e.g. copper, gold
What does electricity flow create?
Energy
Transducer
Device that converts energy from one form to another
Examples of a transducer
Microphone, guitar pick-up, our ears, speakers
Insulators
They stop/block the flow of electricity; opposite of conductor
Electrical conductor
Allows electrons to flow easily
How do microphones transduce sound?
Microphones generate a tiny voltage (millivolts) to make electrons move through a wire
Pre-amp amplifies mini volt signal up to _____
Line level
How many volts is line level?
1.23
What’s the meaning of + and ~ in voltage?
+ indicates DC, and ~ indicates AC
What can multimeters measuer?
Voltage, Current, Resistance
What is Resistance an opposition of?
AC & DC current flow
What is Impedance in opposition of?
Impedance opposes AC current
Is Resistance or Impedance considered ‘frequency dependent opposition?’
Impedance
What is the letter and measurement of Impedance?
Z; and Ohms Ω, similar to R
Power
The amount of energy being used or generated in an electrical circuit of Power
What is the letter and measurement of Power?
P; watts
Current
The intensity of electron flow; literally, the number of electrons flowing through a wire in a given period of time
Resistance
The opposition of electrical current flow
If voltage goes up, ______ goes up
Current
If voltage goes down, ______ goes down
Current
What is the basic type of electrical circuit?
Series circuit
Series circuit
An electrical circuit that has just one loop or path for electricity to flow, and all electrons take the same path
Is current the same throughout a series circuit?
Yes
What’s a simple example of a series circuit?
Christmas lights
Parallel circuit
An electrical circuit that has more than one path or loop/branches for electrons to take
Voltage in Parallel Circuits
All branches or loops of a parallel circuit have the exactly same voltage
What is the equation to find total resistance in a parallel circuit?
Rt= Total Volts (E) / Total Amps (I)
What’s a simple example to parallel circuit?
AC power strip
Circuit breaker
Circuit breakers trip to help stop overflowing electricity from burning the house down lol
What is the equation to find total resistance if resistance is the same in all branches?
Rt=R / # of branches in the circuit
Transformers
Electrical components that uses principals of electromagnetic induction to take an existing AC voltage and current, and transform or convert it to another AC voltage with an equivalent amount of power
What is the core of the transformer typically made out of?
Iron
Primary winding
First coil of wire of the transformer, and is the input side
Secondary winding
Second wire of the transformer, and is the output side
What are the first 3 questions you should ask when troubleshooting?
- Is it plugged in?
- Is it turned on?
- Is it turned up?
Direct Current
Electrical current with fixed polarity, therefore all electrons are flowing in the same direction
Alternating Current
Electrical current with changing polarity, therefore electrons change direction flow
What current is blocked by Transformers?
DC
Why is DC blocked by Transformers?
Transformers work by using electromagnetic induction due to polarity changing in AC current to create a magnetic field that moves and expands to go from primary winding to affect the secondary winding, and DC magnetic fields are unmoving because the current is fixed polarity and direction of flow is constant = no magnetic induction.
Why go through a Transformer?
This allows us to change the AC voltage and current levels that are being outputted by the secondary winding
Turns Ratio
How much AC voltage and current flows in the secondary winding versus how much flows in the primary winding is determined by how many times you wrap the wire around the iron coil
If you wrap primary winding 100 times, and secondary winding 100 times, what is the turns ratio?
1:1
What does 1:1 ratio mean in a transformer?
For every one volt applied to primary winding, you will generate one volt in the secondary winding
Isolation transformer
AC in = AC out; used to provide isolation between two components of a circuit (blocking DC currents), and still pass an AC signal from one side of the circuit to another; also used to isolate ground connections and eliminate “ground loop”
Step Up Transformer
Increasing the voltage from Primary winding to Secondary winding
AC in < AC out
Explain an example of what’s happening with a Step Up Transformer (turn ratio)
A transformer with 100 turns of Primary windings and 400 turns of Secondary windings will create a 1:4 ratio, so for every one volt applied to the input, the output will be 4 volts
Step Down Transformer
Decreasing the voltage from the Primary winding to Secondary winding
AC in > AC out
Explain an example of what’s happening with a Step Down Transformer (turn ratio)
A transformer with 100 turns of Primary windings and 10 turns of Secondary windings will create a 10:1 ratio, so for every one volt applied to the input, the output will be 1/10 volts
Standard AC Distribution in the US
120vAC, 60Hz, Single Phase
What current’s symbol is ~ ?
AC
What current’s symbol is ____
——- ?
DC
Impedance Transformer
A high impedance connection in the primary can be made to look like a low impedance connection to whatever is connected to the secondary, and vice versa (low impedance can look like high)
Unbalanced in - Balanced out
(DI Box)
Unbalanced
Primary winding has 2 wires, one wire is the input (with current), and the other wire is grounded
If it is Unbalanced, does it have high or low impedance?
High
Balanced
Secondary winding has two coils of wire joined in the middle - one wire with matching polarity to the primary winding (pin 2), and the other with an opposite polarity (pin 3)
If it is Balanced, does it have high or low impedance?
Low
Does Pin 1 on Impedance transformer have current or ground? If current, is it in polarity or opposite?
Pin 1 is ground
Does Pin 2 on Impedance transformer have current or ground? If current, is it in polarity or opposite?
Pin 2 has current and is in polarity with Primary
Does Pin 3 on Impedance transformer have current or ground? If current, is it in polarity or opposite?
Pin 3 has current and is in opposite polarity with Primary
High impedance connections are considered balanced or unbalanced?
Unbalanced
Low impedance connections are considered balanced or unbalanced?
Balanced
Electric instruments typically have high input and output impedances - what type of cables do they use?
Unbalanced 1/4” TS, Tip/Sleeve cables
Shield wire
Wrapped/braided around the center copper wire of the 1/4” TS & TRS cable
Purpose of a shield wire
It is typically hooked to the circuit ground through the device the cable is plugged into - therefore, it becomes and electrical conductor hooked to ground surrounding the signal carrying wire, and “shielding” it from electromagnetic energy
If you have to send your signal a longer distance, or want extremely low noise transfer, will you use an unbalanced or balanced line signal? Why?
Balanced, because they have low impedance signals
Balanced line signal cables have how many conductors?
3
Is the shield wire part of the signal circuit in a balanced line signal?
No
Is the shield wire part of the signal circuit in an unbalanced line signal?
Yes
In a balanced line cable (XLR) what is Pin 1 connected to?
Shield wire
In a balanced line cable (XLR) what is Pin 2?
Conductor carrying the phase signal - Hot (red)
In a balanced line cable (XLR) what is Pin 3?
Conductor carrying the identical but opposite polarity signal to Pin 2 - Cold (white)
What can we use to change an unbalanced signal to a balanced one?
A transformer
Do condenser mics have transformers built into them?
No, because condenser mics require phantom power (DC), which transformers block
What do condenser mics use to create a balanced signal?
ICA - impedance conversion amplifier
What is considered electronically balanced?
A condenser mic
What type of cable carries balanced line signals?
1/4” TRS Tip Ring Sleeve and TT Tiny Telephone connectors
In a 1/4” TRS, which parts are hot/red, cold, ground?
Tip: hot/red, Ring: cold, Sleeve: ground
Common Mode Rejection
Noise cancellation effect we get by using balanced line signals, cables & connections
Differential Amp
Electronically balanced input preamplifier that inverts one of the two entering signals
Mic cartridge generates unbalanced signal, which is converted by the built in impedance transformer to what?
A balanced line signal
Which two pins out of 1, 2, and 3 help transform an unbalanced signal to a balanced signal?
Pins 2 and 3
After being transformed to a balanced line signal, the signal travels down pins 2 & 3 on the XLR to the differential amp - now what happens to the signal?
Balanced line signal has two signals - one that is in opposite polarity to the other, when it hits the diff amp, it flips the polarity of pin 3 signal, causing it to be matching polarity with pin 2 = larger amplified signal
How does Common Mode Rejection work?
If noise gets past the shield wire, the noise inducing magnetic fields hit both signal carrying wires at basically the same time, so the noise voltages will have the same polarity on both wires. Because it’s the same, the diff amp will invert one of the signals, causing them to be in exact opposite polarity, therefore CANCELLING NOISE
Common Mode Rejection Ratio
A rating of how much noise will be cancelled
What does CMRR rated at -75dB mean?
The noise is being attenuated by 75dB compared to the actual signal you want to amplify
Impedance Matching
To maximise signal transferring efficiency, we must match output impedance of device (mic, instrument, etc.) to the input impedance of the next device (amplifier, speaker, etc.)
e.g. high impedance output don’t do good with low impedance input
Power Supplies
Converts AC to DC
On a standard US 120vAC outlet, there are 3 prongs. Which is which?
Left larger terminal: Neutral/common (white wire)
Right smaller terminal: Hot 120vAC (black wire)
Bottom round terminal: Earth ground (green/copper wire)
What is the voltage between Neutral/common wire and Hot 120vAC wire?
120vAC
What is the voltage between Neutral wire and Earth ground wire?
0vAC
What is the voltage between Earth ground wire and Hot 120vAC wire?
120vAC
List the 4 main reasons for Impedance matching
- Max the transfer of power
- Increase the headroom
- Increase signal:noise
- Increase efficiency
Series Circuit cheat sheet rules
I = stays the same R = add for total E = add for total P = add for total
Parallel Circuit cheat sheet rules
I = add for total R = total E / total I E = stays the same P = add for total
Electromagnetic Induction
A principle that a coil of wire moving through a magnetic field, or vice versa, will induce/generate an AC current
Does unbalanced or balanced have 1 signal wire?
Unbalanced
1/4” TS (tip, sleeve) and examples
Cable used for unbalanced line signals
Instrument cables, shorter cable runs
1/4” TRS (tip, ring, sleeve) and examples
Cable used for balanced line signals
XLR (mic cable), longer cable runs
What is a big benefit of balanced line signals?
CMRR - Common mode rejection ratio
Does a preamp or a power amp have a higher voltage gain?
Preamp
