SIGNALS SYSTEMS IN MUSIC - Rowan University - …users.rowan.edu/~mease/courses/ssms10/HWSW_Guide.pdf · P.Mease 2010 | Signals & Systems in Music | HW/SW Guide 3 INTRODUCTION & BACKGROUND

P.Mease 2010 | Signals & Systems in Music | HW/SW Guide 1

Introduction &

Hardware/Software Reference

SIGNALS & SYSTEMS IN MUSIC

CREATED BY P. MEASE; LATEST UPDATE: 1.29.10

FOREWORD

This guide will teach you the basic background material and walk you through the required

hardware and software we will use for the course. This includes coverage of: audio interfaces

(UA-25EX), MIDI controllers (Axiom 49), Digital Audio Workstation (DAW) (Reaper), VST Plugins

(Daedalus and Monolisa), the oscilloscope, and function generator. This guide is partitioned in

sections and should be used as a reference throughout the semester.

This guide is written in a detailed, step-by-step format. This can be a bit tedious at first, but will

tell you exactly what you need to do to get the tasks at hand completed properly. This guide is

intended as a basic quick-start for using the tools; many advanced topics are left for you to

discover!

To fully master all of the features of a DAW, for example, requires hundreds of logged hours.

You won’t need this level of skill, but you will need to spend time outside the lab to get proficient

using the tools. If you become fluent with these tools, the possibilities are endless for creating

new sounds and music!


TABLE OF CONTENTS

Signals & Systems in Music; Latest Update: 1.29.10 ............................................................................................... 1

Foreword ....................................................................................................................................................................... 1

Introduction & Background ........................................................................................................................................... 3

Software Installation ..................................................................................................................................................... 6

Initial Audio Setup ......................................................................................................................................................... 7

MIDI & Virtual Synthesizers ......................................................................................................................................... 11

Recording MIDI ............................................................................................................................................................ 16

Recording Audio .......................................................................................................................................................... 19

Rendering your Project to Audio ................................................................................................................................. 22

Using an Oscilloscope .................................................................................................................................................. 23

Using a Function Generator ......................................................................................................................................... 25

Links & Other Resources .............................................................................................................................................. 26

A Final Word ................................................................................................................................................................ 26

Safety & Lab Protocol .................................................................................................................................................. 26


INTRODUCTION & BACKGROUND

This course will cover many topics and introduce you to several tools that will allow you to record, analyze, create

audio, compose entire songs, and even bring that song to a final master. This course will deal with two types of

signals: those that are analogue and those that are digital.

An analogue signal is continuous. This means there are no gaps or discontinuities present anywhere. Examples of

analogue signals include sound waves coming from a speaker, light, human speech, electrical signals in the brain,

etc… These signals have information, or ‘content’ at any time you want to look. Example: if you wanted to look at

time 2 seconds, there would be a value in existence. If you wanted to look at 1594.0913918491842974… seconds,

there would also be a value available. Ideal analogue signals have infinite resolution. A continuous sinusoid is

shown in Figure 1.

FIGURE 1. CONTINUOUS SINUSOID

Conversely, a digital signal is not continuous as shown in Figure 2. Digital signals are very common; as a matter of

fact most of the signals we deal with and can perform math on are digital. Almost all signals in your computer are

digital signals. Music playback devices such as the iPod also deal with digital audio files.

FIGURE 2. DIGITAL ‘SAMPLED’ SINUSOID

Since many processes are done in the digital domain (and nowadays on a computer), we need a way to get these

analogue signals converted to digital ones. For analogue audio signals (such as a piano, voice, etc…), we use an

analogue-to-digital converter (ADC). This little guy is typically a small chip that performs the conversion. It takes


the analogue signal (which is continuous, remember?), samples it at fixed time intervals, and then sends the

samples out. A super high-tech representation of the sampling process is outlined in Figure 3.

FIGURE 3. SAMPLING

You may be asking why we would want to do this conversion. There are many reasons, but it is mainly one of

practicality. Continuous signals take infinite storage space (since the size between every value is infinitesimally

small). Infinite storage is not possible! On the flip side, digital signals have a finite amount of data points or

samples. We can store a finite amount of data points. In this course, you will use an audio interface to perform

this conversion (as well as many other things!).

So now we have our digitized audio and have a bunch of digital bits of information (just ‘ones n zeros’). This is

great for our computer because it is its native language. But once the computer is done talking with our digital

signal, how to we actually hear it again? Simple! Take ‘ADC’ and flip it around: ‘DAC,’ which is short for digital-to-

analogue converter. This little device takes those digital levels and converts them into continuous analogue signals

that can be played through a speaker for our ears to hear. Later in the course we will find that some DACs are as

simple as a 2-component passive low-pass filter... but we won’t worry about filters just yet.

To edit, arrange, create, and play audio and MIDI files we use a Digital Audio Workstation (DAW). A DAW is a

software package that is coupled with hardware for recording and playback of multi-track audio/MIDI. It can also

be used to arrange and compose songs. In this course, we will use a software DAW called Reaper to record and

edit audio/MIDI and will be the host platform for software-based synthesizers.

A synthesizer is an electronic instrument that produces sound by the combination/modulation of signals at various

frequencies. Most commonly ‘subtractive synthesis’ is used where a very full signal is used to start, then

throughout the signal chain, certain components of the signal are modified/removed. There are many types of

synthesizers available but they can generally be clumped into 2 categories: hardware synths and virtual or

software-based synthesizers. The Rowan Doepfer A-100 Modular Analogue Synthesizer can be seen in Figure 4.


FIGURE 4. ROWAN DOEPFER A-100 ANALOGUE SYNTHESIZER

Mod synths such as the Doepfer shown above require manual patching from module to module using physical

cables. While the patching and tonal possibilities of a monster synthesizer such as this are virtually endless, it

requires detailed knowledge of each individual module to operate. These systems are also very expensive,

relatively large, and there exists no quick or easy method to ‘store’ a patch setting.

In this course we will use both but we will use the virtual or ‘soft’ synth more often. These synthesizers run on

your computer through a DAW such as Reaper as a Virtual Studio Technology (VST) plugin. We will be using 2 VST

synthesizers in this course: the Monolisa (Figure 5) and Daedalus (Figure 6) created by Jörgen Arvidsson. These

synthesizers use MIDI for control and the ‘patching’ is done internally for you, making for a much simpler interface.

FIGURE 5. MONOLISA MONOPHONIC VIRTUAL SYNTH


FIGURE 6. DAEDALUS POLYPHONIC VIRTUAL SYNTH. THESE SYNTHS WEIGH NOTHING!

MIDI (Musical Instrument Digital Interface) is a standard protocol for controlling many types of musical instrument

sounds by use of a MIDI controller. These signals are digital and contain no direct analogue audio information.

Instead, MIDI stores note onsets (what note was played) and velocity (how hard the note was played) which can be

used to drive ANY MIDI controllable synth. This is very powerful as it allows great portability and control over

many types of instruments. As an example of this point, a saxophone can only play saxophone sounds no matter

who plays it or what is played. If you take the same notes written to MIDI, you can send it to any type of

synthesizer – a virtual saxophone, trumpet, guitar, motograter, or even drums. The downside to MIDI is that is

typically not as dynamic as an acoustic instrument (although electronic instruments are their own class of unique

instruments altogether). MIDI also assumes you are using powerful synthesizers to generate quality sounds.

A function generator is an instrument that is capable of outputting various signals such as sin, saw, triangle,

square, noise, etc… An arbitrary function generator is capable of receiving user-defined waveforms and ‘playing’

them. At the genesis of the synthesizer, lab-grade function generators were used and modified.

An oscilloscope is an instrument used to monitor time-varying signals. The modern oscilloscope takes input from

the ‘real world’ and converts them to digital signals using an ADC. Most oscilloscopes can perform many other

math functions onboard, which we will exploit.

SOFTWARE INSTALLATION Before we can do anything, we must first install all of the required software for the course. There are several

packages, so please follow this guide carefully. We will be installing the software in this order:

Music/Audio Software:

1. Reaper


2. Cakewalk UA-25EX USB Driver

3. Axiom 49 USB MIDI Driver

4. Monolisa

5. Daedalus

Engineering Software:

6. Agilent IO Libraries (for connecting to any Agilent instrument)

7. Agilent Hardware Driver (driver for Agilent modular scopes)

8. Agilent AMM (for using the Agilent modular scopes)

9. Agilent Intuilink (for connecting to scopes in Mixed Signals Lab – Room 206)

System Requirements: The requirements for all packages to work are Windows XP 32bit, Vista 32bit, 7 32bit. The

Agilent software will NOT work on a 64bit platform, however Reaper and the other audio software will. The PC

must also have at least 3 functional USB ports to use all devices at the same time.

- ‘Run’ the software (contains all of the above software) from the following link by clicking icon next to each

download. All of the downloads are available at the following link:

http://users.rowan.edu/~mease/resources/ssmsw.html

- Install each of these packages in the specified order, as given in the above page. Use the default

installation instructions and follow any prompts to plug in hardware as guided. If they are in zip folders,

just open the folder and click on the setup file.

- NOTE! The Monolisa and Daedalus synths (packages number 4 and 5) are NOT installable type files. To

‘install’ this software, you must copy the contents of the zip folder to: C:/Program Files/REAPER/Plugins/

INITIAL AUDIO SETUP Required: Cakewalk UA-25EX Interface, PC, Reaper, Headphones or Powered Speakers, (Headphone Distribution

Amp)

- Connect a USB cable from the UA-25EX audio interface (Figure 7a) to your computer. The interface is

powered by the USB port on your computer so no power adapter is required. NOTE: USB driver must

be installed first (see Software Installation above)!

- On the back panel of the UA-25EX, the following switches should be set as follows (see Figure 7 for

correct positions):

1. The ADVANCED DRIVER (Figure 7b) switch should be in the ON position! If the ADVANCED

DRIVER switch is in the off position, you will not be able to record using the ASIO driver,

which is what we will want.

2. The GROUND LIFT (Figure 7c) switch should be in the NOR position.

3. PHANTOM (Figure 7d) switch should be OFF (unless recording with a mic that requires

phantom power)

4. The SAMPLE RATE (Figure 7e) switch should be in the 44.1 position (all the way right)



FIGURE 7. CAKEWALK/EDIROL UA-25EX AUDIO/MIDI INTERFACE – BACK PANEL

- Now we need to connect the audio output from the ‘PHONES’ jack (Figure 10a below) to headphones

OR to the headphone distribution amp (Figure 8) if you are working in a group and need more than

one person to hear at a time. You may use speakers if you are using the setup without any other

teams around.

FIGURE 8. ART HEADAMP4 HEADPHONE DISTRIBUTION AMP

- To use the headphone distribution amp, connect a 3.5mm stereo cable from the PHONES output of

the UA-25EX (Figure 10a) to the STEREO IN jack (Figure 9a) of the ART HeadAmp4 distribution amp.

The headphones connect to the ONE, TWO, THREE, or FOUR jacks on the back (Figure 9b).

a b

c

d

e


FIGURE 9. HEADAMP4 - BACK PANEL

- NOTE: When using the headphone amp, make sure the volume controls on the front panel are fully

CCW (counter-clockwise). ONLY ADJUST THE VOLUME FOR THE HEADPHONES THAT ARE ON YOUR

OWN HEAD! Listening to audio with headphones at high volumes can cause permanent hearing loss.

You do not want to cause hearing damage to other people.

The front panel of the UA-25EX has several controls:

- The SENS knob (Figure 10b) adjusts the input gain of either INPUT 1/L or INPUT 2/R, respectively. You

would use INPUT 2/R with the Hi-Z switch pressed in if you were plugging a guitar directly into the

box.

- The COMP/LIMIT knob (Figure 10d) adjusts the internal compressor limit threshold. Typically, we do

not want this active since it will alter the dynamics of the signal; a compressor will ‘squash’ the signal

so that it isn’t allowed to get to high. Adjust this so that it is in the ‘OFF’ position. You can also

disable it by the switch on the rear panel. You may want to use this feature later, but for most

applications it is not entirely necessary.

- The MONO switch (Figure 10e) should be in the out position if you are recording stereo (a right and

left channel).

- The MON SW (Figure 10f) is used for either monitoring the incoming signals at the INPUT jacks

directly (when red LED next to VOLUME is on) OR sending all audio to the DAW and listening to the

output of the audio through the DAW.

- The VOLUME knob (Figure 10g) is used to control how much of the input signal is mixed to the main

output and is only relevant when the MON SW is on and you are direct monitoring.

- The OUTPUT knob (Figure 10h) is used to control the main volume sent to the headphones and the

output jacks on the back of the unit. Now read the above 3 paragraphs a few more times…

a b


FIGURE 10. CAKEWALK/EDIROL UA-25EX AUDIO/MIDI INTERFACE – FRONT PANEL

- Open Reaper on the host machine (if it is not installed, install it first, then reconnect the UA-25EX,

then start the program). If you are using the evaluation version, the evaluation window will pop up

as shown in Figure 11 below.

FIGURE 11. REAPER EVALUATION SCREEN

- Click the close ‘X’ and again after the timeout expires. NOTE: If you are using Reaper past the 30 day

evaluation, you are required to purchase the software.

- Click File>New Project. Now click on Options>Preferences>Device under the Audio heading. The

Audio device settings window will pop up (Figure 12). The Audio system should be ASIO and the ASIO

driver should be ‘EDIROL UA-25EX.’ The Enable Inputs box should be checked. Keep the remaining

items to their default settings, then click ‘OK.’ This is tiring, how about a picture instead:

a b b

c d

g

e f h


FIGURE 12. AUDIO DEVICE SETTINGS

- Once this is completed, you should be able to play and record audio in Reaper. This must be

completed before using Reaper in any capacity that requires audio input or output. Remember to

connect and power-on any MIDI/Audio devices before opening Reaper!

MIDI & VIRTUAL SYNTHESIZERS The first thing we will figure out how to do is use the MIDI controller to control a software VST (Virtual Studio

Technology) synthesizer in Reaper.

Required: Cakewalk UA-25EX, PC, Reaper

- Before we can use any synthesizer plug-ins, we must first tell Reaper where they are. Open Reaper.

- Click Options>Preferences>Plugin>VSTi in the tree on the left. In this window (Figure 13), click Add…

then navigate to the C:\Program Files\REAPER\Plugins folder. Now click Rescan Directories. If you

placed the synths (as directed) into this folder, Reaper will now find them. Press OK to close out of

this window.


FIGURE 13. VST PLUG-INS SETTINGS WINDOW.

- Click Insert>New virtual instrument on new track… In the window that pops up (Figure 14) under the

All Plugins heading on the left, click on Instruments (or VSTi) and open the Monolisa synth by double

clicking VSTi: Monolisa.dll.

FIGURE 14. INSERT VIRTUAL INSTRUMENT ON NEW TRACK WINDOW


- This will add the VST synth to a new track in Reaper. We now want to give the track a space for MIDI

data to be stored, which will trigger notes in the Monolisa synth. To do this, click Insert>New MIDI

item in Reaper with the track selected. You will now see a block added to the Monolisa track in the

Track view (Figure 15). This block is where MIDI data will be stored. You can also manually add and

edit MIDI notes individually here. Let’s do this… double click this block:

FIGURE 15. MIDI TRACK IN TRACK VIEW

- After double clicking the block you will see the MIDI editing window, commonly called the piano roll

view (PRV) (Figure 16). This cell matrix includes notes (y axis - the columns) and the time/duration (x

axis – the horizontal rows). With the speakers/headphones on, move your mouse at various locations

throughout the cell matrix to hear different pitches coming from the Monolisa synthesizer.

This is the MIDI block

on the Monolisa

track. Double click.


FIGURE 16. PIANO ROLL VIEW (PRV)

- The above PRV shows notes as MIDI numbers. These numbers correspond to actual notes on a piano.

To see this instead of the numbers press Alt+1 or click View>Mode: piano roll. This should now look

like Figure 17.

FIGURE 17. PRV WITH PIANO KEYS

Notes - lower notes

are at the bottom,

higher pitches at

the top

Time – cells are divided into measures

and time signature durations. Notes

will snap to this grid by default


- Now let’s place some notes. This is done by hovering the mouse over the cell you want the note

placed and double clicking. You can delete the note by selecting it and hitting the delete key or

pressing undo (Ctrl+z)

- Add notes as shown in Figure 18 below. Be sure to place ¼ notes (four per measure). Measures are

denoted by the major numbers directly above the grid space in the PRV:

FIGURE 18. PRV WITH NOTES ADDED

- You need to note (npi!) several things here:

1. The big bar running vertically in the PRV is the loop length bar (Figure 18a). The location of

this bar tells the MIDI track when to repeat (go back to the beginning. You can move this bar

to control the total length of the MIDI segment in the track view (Figure 18b). In the track

view, the loop segment is denoted by the little triangular ‘cuts’ from the MIDI segment

chunk. To play more of the loop you’ve made in the MIDI PRV view, simply drag the end of

the MIDI segment in the track view (Figure 18c).

2. This is a simple C major scale. The last octave C is held longer (dotted half instead of quarter

(Figure 18d). To do this: place the note then drag the end of the note longer.

- Now play the file you’ve just created by pressing the space bar or by clicking on the play button in the

transport (located in track view). You should hear to notes you’ve placed.

- Experiment further with different notes, loop lengths, zoom in/out, etc…

- You can now open the interface for the Monolisa synthesizer and change the sound by loading

presets or manually adjusting the soft-knobs. The soft-synth windows can be re-opened at any time

by clicking the fx button in the corresponding track in the track view as shown in Figure 19.

a) Loop length bar

b) Track view’s end of

loop for MIDI segment

d) Dotted half-note

c) Drag here to play more…


FIGURE 19. BRINGING UP THE VST PLUGIN SCREEN

- We will discuss this (and other) synthesizers in more detail later in the course.

RECORDING MIDI Manually placing MIDI notes one by one is effective and sometimes handy; however, it can be a bit tedious for

length passages. If you knew how to play piano (or any other MIDI controller’s instrument format) you can simply

record the MIDI notes directly from the controller in real-time. This guide will show how we do this.

Required: Cakewalk UA-25EX, PC, Reaper, M-Audio Axiom 49 MIDI controller, USB or MIDI cable

- Before starting Reaper, make sure your MIDI controller’s driver is installed, and the controller is

connected to the computer. The Axiom 49 can be connected by USB (Figure 20a) OR MIDI cable

(Figure 20b). USB is usually easiest, so we’ll use that. Windows will output successful connection

when you plug in the USB from the Axiom indicating that it sees and can communicate with the

Axiom. The Axiom will also light up.

fx button

Virtual synthesizer

user-interface window

(Monolisa)


FIGURE 20. AXIOM 49 - BACK PANEL

- NOTE: if the USB driver for the Axiom is not supported by your OS, you are forced to use a standard

MIDI cable. This requires you to use the UA-25EX MIDI ports on the back, connected to the MIDI

ports on the Axiom 49. Also, you will have to power the controller externally with a 12VDC power

adapter (USB connectivity is self-powered by the USB buss of the computer).

- Open Reaper (make sure the audio interface is also first connected!). Click Options>Preferences… In

the window, click on MIDI Devices under the Audio tab. A window (Figure 21) will pop up:

FIGURE 21. MIDI DEVICES WINDOW

- In this window you will see all connected MIDI devices. Right click the Axiom 49 under MIDI inputs

and Enable it. The Axiom can also receive output MIDI control messages from Reaper, but for now,

we will leave this disabled. Click OK.

- Now insert a new MIDI virtual instrument track (see the MIDI & Virtual Synthesizers section).

Typically, Reaper will find the MIDI input from the controller automatically. To do this manually (or to

double check), click the record arm button on the track and then the drop-down combo box as shown

in oijoij0230.

a b


FIGURE 22. INPUT DROP-DOWN

- Click MIDI Input>Axiom 49>All Channels to select the Axiom as the MIDI input for the track.

- Now (again the track’s record arm must be enabled) you can see MIDI activity in the meter on the

track as shown in Figure 23. It will show up red. The other levels in the meter are the audio output

levels from the VST synthesizer.

FIGURE 23. MIDI ACTIVITY

- To record MIDI from the controller, make sure the track record arm is enabled, then click the main

record arm on the transport (Figure 24) and get playin!

FIGURE 24. MAIN RECORD ARM – TRANSPORT

- Recording MIDI (and audio!), you typically use the metronome to keep time. A metronome is used to

provide the performer with accurate time pulses (usually audible clicks) so that he/she plays on time.

MIDI Activity

Audio Activity


To enable the metronome, you need to do 2 things: 1) Enter the tempo you wish to play and 2)

enable the metronome in the DAW.

- To enter the tempo, type in the value you wish to use in the BPM text box shown in Figure 25. NOTE:

This tempo setting adjusts the tempo for the entire project.

FIGURE 25. WHERE TO ENTER BPM

- To enable the metronome output while recording click the metronome icon circled in Figure 26.

FIGURE 26. METRONOME ICON

That’s about it!

RECORDING AUDIO Here is a guide for recording audio onto your computer using Reaper and the UA-25EX. Be sure to follow all steps.

Required: Cakewalk UA-25EX audio interface, PC, Reaper, Microphone or Line-Level Instrument/Device

- Open Reaper and click on ‘Track>New Track’ (or Right Click on the track pane or just hit Ctrl-T). Now

click on the Record Arm ‘R’ Button on the channel strip and then the little speaker icon (Figure 27):


FIGURE 27. ARMING THE TRACK

- You can change the channel to record from by clicking the drop-down box, although it usually

defaults to the first input.

- Connect the microphone or line instrument cable to either INPUT 1/L or INPUT 2/R (Figure 28 a, b).

Connecting to INPUT 2/R will require you to change the input channel in the track in Reaper (see

above). If you are using a condenser microphone that requires phantom power (ask!), you need to

slide the PHANTOM switch on the back panel (Figure 7) to the +48 setting.

FIGURE 28. CAKEWALK/EDIROL UA-25EX AUDIO/MIDI INTERFACE – FRONT PANEL

- Now set the UA-25EX ‘SENS’ knob for the channel you want to record with to the halfway point. Set

the ‘OUTPUT’ knob low, then slowly increase the volume, while talking into it. If it is faint, increase

the channel gain. Monitor the VU meters in Reaper (circled in Figure 29). If it is in the RED, turn the

SENS knob on the UA-25EX down (CCW).

a b


FIGURE 29. TRACK VU/LEVEL METERS

- TIP: Be sure the recorded audio is not clipping (especially with loud instruments or sensitive

microphones). Clipping is when the amplitude limits of the transducer (the microphone), the ADC

(interface), and/or the DAW are exceeded. This is BAD and the original signal cannot be recovered,

furthermore, it will sound really BAD. Fortunately, all you have to worry about are the gain controls

on the interface and in the software. Make sure the meters on both the interface and the DAW are

not ‘in the red’ and you’ll be good. You also don’t want the VU meter reading too low for your

specific recording application. It should be as close to 0dB without going over.

- Now you are ready to record audio! All you need to do now is click on the main record button in the

transport (Figure 30). You stop it by clicking it again, or by using the stop button. You should get

something that looks like this:


FIGURE 30. MAIN RECORD ARM IN THE TRANSPORT

- You can play back your recording by hitting the Play button, or by using the spacebar. Typically, a

metronome is used to record passages on-time. See the Recording MIDI section of the guide to learn

how-to use the metronome.

RENDERING YOUR PROJECT TO AUDIO When you complete your project and want to combine all of the tracks into one single audio file (like a mp3 on

your iPod), you need to render the tracks. A very common high-fidelity output format is the .wav. We will be

rendering the audio to this format. If you want to render to mp3, you will have to find the appropriate CODEC or

convert the .wav file to mp3 using a 3rd

party converter. This will not be covered here.

- First ensure that any track you wish to be outputted is not muted. Click File>Render… The window in

Figure 31 will pop up:

This is recorded audio


FIGURE 31. REAPER RENDER SETTINGS

- The default settings are usually fine. The only thing you may wish to change is where the file will be

saved. This can be changed in the Output file path.

- Click Render.

USING AN OSCILLOSCOPE An oscilloscope is a powerful tool used to view time-changing signals. These can be analogue or digital signals

(although in reality, they are all analogue signals). The oscilloscope views this data just like an x-y plot, where the x

direction (vertical) shows the voltage or amplitude of a signal and the y direction (horizontal) is the time. All

oscilloscopes have (at least) the fundamental control sections: Vertical, Horizontal, and Trigger. In addition, some

scopes have math functions built-in which we will use later.

Signals are connected to the oscilloscope using a BNC type connection. The BNC port on the scope can be seen in

Figure 32.

FIGURE 32. BNC INPUTS


We can connect two types of cables to the inputs: a BNC or a Scope Probe. These are displayed in Figure 33.

FIGURE 33. BNC TO BNC CABLE (LEFT) AND SCOPE PROBE (RIGHT)

- Connect the appropriate cable to the input BNC of the scope (pick a channel). The type of cable to

connect will depend on what you are measuring and how probing is to be performed.

- The other end of the cable will go to the source of measurement. If you are using a scope probe, be

sure to connect the ground lead to an appropriate ground.

With your signal now connected to the oscilloscope, we must scale the horizontal and vertical space so that we are

looking at the area of interest of the signal. This is straightforward but does require some prior user knowledge to

set properly. For this guide let’s assume we are trying to find a sinusoid that is oscillating at a frequency of 1kHz

and has an amplitude of 1Vpp. Even if you didn’t know this information exactly, you should have a rough estimate

of these parameters… i.e. if you were looking at a cell phone signal, you would search in the GHz range. If you are

looking for an audio signal, it will be somewhere under 20kHz.

The front panel of the Agilent Infiniium series oscilloscope is shown in Figure 34.

FIGURE 34. OSCILLOSCOPE FRONT PANEL

a

b

c d

e

f g h

i


- Hit the auto scale button on the front panel (Figure 34a). This will automatically scan the inputs and

set the horizontal and vertical settings for you. This feature works most of the time, but is typically

only reserved for quick viewing of very basic signals. You must be very careful using this feature and

check what it gives you as it can zoom in on noise, which is present in any signal.

- To adjust the vertical (amplitude) zoom manually, rotate the vertical knob (Figure 34b) on the front

panel of the oscilloscope. Take note that this changes the Volts/ value (Figure 34c). This value

displays ‘Volts per division’ of the grid lines on the scope screen. The space between each horizontal

grid line represents this value.

- To adjust the horizontal (time) zoom, rotate the horizontal knob (Figure 34d) on the front panel. This

changes the Time/ value (Figure 34e). This value represents how much time the space between each

vertical grid line designates.

The trigger section of the oscilloscope is used to lock or sync to a waveform. This can be used to keep periodic

signals from ‘bouncing around’ or even to capture single random ‘glitches.’ For this guide, we will only explain how

to lock a periodic waveform.

- Make sure that the sweep mode is set to Auto (Figure 34f) and the source (Figure 34g) is set to the

channel your signal is inputted to.

- Rotate the level knob in the trigger section (Figure 34h) on the front panel of the oscilloscope. You

will see a horizontal line moving on the scope display. Move this line until it intersects the waveform.

If the intersections are periodic, then it will lock in on the waveform and keep it still. NOTE: This is

NOT the same as pressing the Stop button (Figure 34i), which stops any further acquisition.

USING A FUNCTION GENERATOR A function generator is an instrument used to generate and output basic waveforms. The user can adjust the

frequency, offset, amplitude, and many other parameters of the signal. Some function generators allow arbitrary

waveforms to be sent to them, allowing outputting of much more complex signals. Here we will discuss basic

usage. We will use the HP/Agilent 33120A as shown in Figure 35 for demonstration.

FIGURE 35. HP/AGILENT 33120A FUNCTION GENERATOR - FRONT PANEL

a

b

c

d e f


- First, let’s create a simple sinusoid with amplitude of 5Vpp and frequency of 2.5kHz. Click the sinusoid

button (Figure 35a) on the front panel.

- To adjust the frequency of the sinusoid press the Freq button (Figure 35b) then rotate the encoder

wheel (Figure 35c) to adjust the value in the blinking digit on the display. To move the active digit,

use the right and left arrow buttons (Figure 35d). Adjust till the frequency is 2.5kHz.

- To adjust the amplitude of the signal, press the Ampl button (Figure 35e) and adjust the value to 5Vpp

using the encoder wheel.

- To use the signal we connect a BNC cable from the output connector (Figure 35f) to, well, wherever

you need the signal!

- You can use the same process for the other wave types next to the sinusoid button: square, triangle,

saw, and noise. This function generator is also capable of AM/FM modulation and receiving arbitrary

waveforms created on a host computer.

LINKS & OTHER RESOURCES Course webpage: http://users.rowan.edu/~mease/courses/ssms10/ssms10.html

Instrument connectivity: http://users.rowan.edu/~mease/resources/instrconn.html

Comprehensive Reaper User’s Guide: http://www.reaper.fm/userguide/ReaperUserGuide316.pdf

Course software download page: http://users.rowan.edu/~mease/resources/ssmsw.html

A FINAL WORD There will be lots of new material presented in this course and requires you spend time reinforcing these concepts

outside of class. Do not hesitate to immediately contact the instructor(s) if you have any questions on anything.

Don’t be shy!

Come back to this reference for help with any of the topics found in the Index.

SAFETY & LAB PROTOCOL - Be sure to turn down any headphone volumes BEFORE putting them on your head!

- If using the headphone distribution amp, be sure to notify others wearing connected headphones

when you are going to play something

- Do NOT adjust any other headphone volume control but your own

- Return all cabling neatly to the racks

- Clean your workspace when finished your experiment

- No food or drink allowed in the lab

- Take extreme care handling the instruments

- And remember kiddies, don’t stare directly at Tiny Tim:

http://users.rowan.edu/~mease/courses/ssms10/ssms10.html

http://users.rowan.edu/~mease/resources/instrconn.html

http://www.reaper.fm/userguide/ReaperUserGuide316.pdf


Documents

SIGNALS SYSTEMS IN MUSIC - Rowan University - …users.rowan.edu/~mease/courses/ssms10/HWSW_Guide.pdf · P.Mease 2010 | Signals & Systems in Music | HW/SW Guide 3 INTRODUCTION & BACKGROUND