Making all the right connections
Making all the right connections
Signal Flow 101Signal Flow 101
What is Audio Signal Flow?What is Audio Signal Flow?
Audio: “Of or relating to sound or sound reproduction” – Webster’s II New Riverside Dictionary
Audio Signal: “a representation of sound waves in a different form. Typically this is an electrical voltage…An audio signal can be manipulated, stored, transmitted and reproduced in ways that a sound wave cannot.” - http://en.wikipedia.org/wiki/Audio_signal
Audio Signal Flow: “the term used to describe the path an audio signal will take from source (microphone) to the speaker or recording device.” - http://en.wikipedia.org/wiki/Audio_signal
Audio: “Of or relating to sound or sound reproduction” – Webster’s II New Riverside Dictionary
Audio Signal: “a representation of sound waves in a different form. Typically this is an electrical voltage…An audio signal can be manipulated, stored, transmitted and reproduced in ways that a sound wave cannot.” - http://en.wikipedia.org/wiki/Audio_signal
Audio Signal Flow: “the term used to describe the path an audio signal will take from source (microphone) to the speaker or recording device.” - http://en.wikipedia.org/wiki/Audio_signal
Rules of Signal FlowRules of Signal Flow
Rule #1: Things always work better when they are plugged in…
Rule #2: Outputs are connected to Inputs (and vice versa)
Basic Plumbing - the signal only flows in one direction
Follow the electrons (hint: they’re inside the cable)
Audio signals require at least two wires: one for signal and one for ground
(Don’t confuse WIRE with CABLE – one CABLE can contain several wires)
Rule #1: Things always work better when they are plugged in…
Rule #2: Outputs are connected to Inputs (and vice versa)
Basic Plumbing - the signal only flows in one direction
Follow the electrons (hint: they’re inside the cable)
Audio signals require at least two wires: one for signal and one for ground
(Don’t confuse WIRE with CABLE – one CABLE can contain several wires)
Common Audio Connectors
Common Audio Connectors
Balanced (professional equipment) XLR 1/4-inch TRS
Unbalanced (consumer equipment) 1/4-inch TS RCA
Balanced (professional equipment) XLR 1/4-inch TRS
Unbalanced (consumer equipment) 1/4-inch TS RCA
Balanced vs. UnbalancedBalanced vs. Unbalanced
An audio cable is an antenna - it picks up noise along its length
The signal cannot be separated from the noise on an unbalanced signal
A balanced signal can eliminate this noise through “destructive interference”
Unbalanced cables require two conductors,
Balanced cables require three
An audio cable is an antenna - it picks up noise along its length
The signal cannot be separated from the noise on an unbalanced signal
A balanced signal can eliminate this noise through “destructive interference”
Unbalanced cables require two conductors,
Balanced cables require three
“Pin-out” of typical connectors
“Pin-out” of typical connectors
Quarter-inch TS
RCA
Signal Ground
XLR
Quarter-inch TRS
Signal + GroundSignal -
UNBALANCED BALANCED
How noise affects a signalHow noise affects a signal
A bit about “polarity” and “phase”
A bit about “polarity” and “phase”
Sound waves alternate between high pressure and low pressure
Electrical audio signals alternate between positive (+) and negative (-)
Polarity indicates a positive or negative value
Musical Sounds have a repetitive wave pattern - a cycle that repeats
Phase tells us where we are in a cycle Phase is measured in degrees or radians One complete cycle = 3600 of phase
Sound waves alternate between high pressure and low pressure
Electrical audio signals alternate between positive (+) and negative (-)
Polarity indicates a positive or negative value
Musical Sounds have a repetitive wave pattern - a cycle that repeats
Phase tells us where we are in a cycle Phase is measured in degrees or radians One complete cycle = 3600 of phase
How “balanced” worksHow “balanced” works
+ =
Same signal polarity inverted
Same noise
gets into both
signals
Polarity inverted again - signal “in-phase”
noise “out-of-phase”
Signal twice as strong;
noise cancels out
Male vs. FemaleMale vs. Female
use your imagination… With XLR, male tends to be an
output and female tends to be an input
An XLR cable generally has two genders
1/4-inch and RCA cables are generally male at both ends
use your imagination… With XLR, male tends to be an
output and female tends to be an input
An XLR cable generally has two genders
1/4-inch and RCA cables are generally male at both ends
What level is it?What level is it?Every input expects ONE TYPE of level. Mismatching
can result either in distortion or no usable signal Mic level - smallest (-60 dB)
XLR connector Consumer level (-10 dB)
Home stereo equipment VCR/DVD/TV Uses RCA connectors
Line Level - highest (+4 dB) Professional equipment - mixers, preamplifiers,
keyboards, recording equipment, etc. 1/4-inch or XLR connector
Every input expects ONE TYPE of level. Mismatching can result either in distortion or no usable signal
Mic level - smallest (-60 dB) XLR connector
Consumer level (-10 dB) Home stereo equipment VCR/DVD/TV Uses RCA connectors
Line Level - highest (+4 dB) Professional equipment - mixers, preamplifiers,
keyboards, recording equipment, etc. 1/4-inch or XLR connector
Gain StagingGain Staging
Signal must be the right level for the next piece of equipment in the chain Too small = signal lost in noise Too big = distortion (“clipping”)
Gain: “an increase” - Webster’s II New Riverside Dictionary
Any point in the signal chain where the amount of signal can be adjusted (boosted) is called a “Gain Stage”
Mic-level signals must be raised to line-level for recording - “Microphone Preamp”
Signal must be the right level for the next piece of equipment in the chain Too small = signal lost in noise Too big = distortion (“clipping”)
Gain: “an increase” - Webster’s II New Riverside Dictionary
Any point in the signal chain where the amount of signal can be adjusted (boosted) is called a “Gain Stage”
Mic-level signals must be raised to line-level for recording - “Microphone Preamp”
Simple Signal FlowSimple Signal Flow
Preamp Power Amp
(microphone) (speaker)
Channel vs. TrackChannel vs. Track
Channel: “a means of passing, transmitting, or communicating.”
Webster’s II New Riverside Dictionary
Track: a place to store audio information
Where is the signal going? It gets recorded to a track It passes through a channel
Channel: “a means of passing, transmitting, or communicating.”
Webster’s II New Riverside Dictionary
Track: a place to store audio information
Where is the signal going? It gets recorded to a track It passes through a channel
Multitrack RecordingMultitrack Recording
When you are recording to more than one track, this is called multitrack recording
In the recording studio, a number of microphones or sources can be recorded simultaneously
The signal from each mic and/or source can be recorded to a different track so that it can be processed separately and mixed later
You can also record one mic (or source) several times to make it sound like it all happened at the same time (overdub)
When you are recording to more than one track, this is called multitrack recording
In the recording studio, a number of microphones or sources can be recorded simultaneously
The signal from each mic and/or source can be recorded to a different track so that it can be processed separately and mixed later
You can also record one mic (or source) several times to make it sound like it all happened at the same time (overdub)
Mono vs. StereoMono vs. Stereo
Mono literally means “one” Mono is one distinct channel of audio
information Stereo comes from the Greek “stereos”
meaning “solid” or something that has length, width, and height
Stereo is an aural illusion which requires two or more distinct channels of information – one channel for the left; one for the right.
Most things are RECORDED as MONO sources and we use them to create a STEREO mix
Mono literally means “one” Mono is one distinct channel of audio
information Stereo comes from the Greek “stereos”
meaning “solid” or something that has length, width, and height
Stereo is an aural illusion which requires two or more distinct channels of information – one channel for the left; one for the right.
Most things are RECORDED as MONO sources and we use them to create a STEREO mix
Mono or stereo?Mono or stereo? Recording: how many outputs does the
device have? One output = mono. Typically a single
microphone on a single is a MONO source Two outputs could mean stereo. Many electronic
instruments (like keyboards or drum machines) have stereo outputs
A pinpoint source should be recorded mono; something that takes up space left-to-right should be stereo
For your mixes to be stereo, you’ll have to make use of the pan knob to “move” things to the right or left. If everything is panned center, you might have a
MONO mix.
Recording: how many outputs does the device have? One output = mono. Typically a single
microphone on a single is a MONO source Two outputs could mean stereo. Many electronic
instruments (like keyboards or drum machines) have stereo outputs
A pinpoint source should be recorded mono; something that takes up space left-to-right should be stereo
For your mixes to be stereo, you’ll have to make use of the pan knob to “move” things to the right or left. If everything is panned center, you might have a
MONO mix.
Analog RecordingAnalog Recording Comes from the word “analogous” meaning
“similar to” or “the same as” The voltage changes coming from the
microphone will have absolute correlation with the changes in air pressure caused by the sound wave that moved the diaphragm
The fluctuations in the magnetic field recorded onto analog tape will have absolute correlation with the voltage changes from the microphone
Analog records continuously - there is no gap in the recorded information
Comes from the word “analogous” meaning “similar to” or “the same as”
The voltage changes coming from the microphone will have absolute correlation with the changes in air pressure caused by the sound wave that moved the diaphragm
The fluctuations in the magnetic field recorded onto analog tape will have absolute correlation with the voltage changes from the microphone
Analog records continuously - there is no gap in the recorded information
Digital RecordingDigital Recording An Analog signal has a constantly changing value; A Digital signal is a series of pulses of only two values
(on/off) Analog to Digital Converter (ADC) - takes regular
measurements of the analog signal (samples) and converts each measurement to a numeric (digital) value
The value of each sample is indicated by a pattern of on/off pulses
The series of samples is then stored (recorded) Digital to Analog Converter (DAC) - converts the digital
signal back to a continuous analog signal More on this later…
An Analog signal has a constantly changing value; A Digital signal is a series of pulses of only two values
(on/off) Analog to Digital Converter (ADC) - takes regular
measurements of the analog signal (samples) and converts each measurement to a numeric (digital) value
The value of each sample is indicated by a pattern of on/off pulses
The series of samples is then stored (recorded) Digital to Analog Converter (DAC) - converts the digital
signal back to a continuous analog signal More on this later…
TYPICAL SIGNAL FLOW IN A DIGITAL AUDIO CHAIN
A computer needs a soundcard (aka Audio Interface) to receive or send audio signals. Often, the computer acts as a Digital Recorder. Usually, the soundcard will convert the signal from ANALOG to DIGITAL for the computer. Then, it converts the DIGITAL signal from the computer back to ANALOG to be played back for humans
A computer soundcard can be internal or external. Many external soundcards use Firewire or USB. All computer soundcards have ADC’s and DAC’s built into them. Some soundcards even have built-in preamps.
Preamp
ADC
Power Amp
Computer/Recorder
DAC
(microphone)
(speaker)
SO
UN
DC
AR
D
(headphones)
SummarySummary Signal only flows in one direction Outputs are connected to inputs There are three basic signal levels: mic (-60dB),
consumer (-10dB), and line (+4dB) Unbalanced signals: 2 conductors - signal and ground;
CANNOT eliminate noise picked up on the cable Balanced signals: 3 conductors: signal + , signal - , and
ground; CAN eliminate noise picked up on the cable We record most things as mono sources; we use them to
create stereo mixes Gain Staging: optimizing the signal level for the next
device in the signal chain
Signal only flows in one direction Outputs are connected to inputs There are three basic signal levels: mic (-60dB),
consumer (-10dB), and line (+4dB) Unbalanced signals: 2 conductors - signal and ground;
CANNOT eliminate noise picked up on the cable Balanced signals: 3 conductors: signal + , signal - , and
ground; CAN eliminate noise picked up on the cable We record most things as mono sources; we use them to
create stereo mixes Gain Staging: optimizing the signal level for the next
device in the signal chain