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