EMS: Electronics for Music Synthesis

Final Project – Spring 2010

For the project, you will design and build a synthesizer module to
expand our existing modular system.

You will be allowed to
use existing schematics you find from the web and elsewhere, but you cannot
just build a given schematic verbatim. You can do one or a combination of
the following:

(a) You could “modularize” part of a complete synthesizer circuit (i.e. build
a module based on the VCO, VCF, or whatever of a
subcircuit of a complete synthesizer).
This may
involve adding/modifying input and output circuitry so that the resulting
module matches the specifications given below, and also may involve “updating”
the circuit to use modern parts. If you take this route, I will want to make
sure that a modularized version doesn’t obviously already exist on the web.

(b) You can use an existing modular synth circuit, but you must make some
interesting “twist” on the design.
In particular,
you can create a design that combines elements from two different existing
designs (the “crossbreed”), makes a fundamental change
in an existing design (the “mutant”),
or both (the “crossbreed mutant”).

(c) You can do something more original. If you’re doing a project that is based
less on existing proven designs, I will put priority on helping you out during
the design process.

You must be sure to give credit to
the original inspirations of your designs wherever
possible. If you
eventually consider marketing your design (say, starting a business
to sell boards), karma demands that you discuss sharing a portion of your
with the original sources of your design. (As mentioned in class, schematics
can be
but circuits can’t, so if a circuit isn’t patented, you can legally
use it
and sell it however you like – but what’s morally the right thing to do
is a different story.)

You aren’t constrained to use any existing designs if you don’t want to.
If you are feeling adventurous and want to
try making something
up out of thin air, or some combination of thin air and existing
designs, that’s
OK. I’m allowing you to make such extensive use of
existing designs since (a) most of the synth
I know of actually got their start from tinkering around and modifying older
designs, and (b) we’re getting started so late because the recent arrival
of Zachary Xavier Lanterman is taking up so much of my time and mental

Your module must either make audio (i.e. an oscillator) or process audio
(i.e. a filter or nonlinear waveshaper) or sometimes both (i.e. a filter that
self-resonates when the Q is turned up really high).
Since this will be a component of a synthesizer, some aspect of your module
should be controllable via a control voltage. (For instance, a filter
whose cutoff is solely controlled by a pot won’t do.)

Here is an extensive
list of
project ideas
You shouldn’t by any means feel restricted to pick something on
that list (which I’ll keep adding to as random ideas strike me);
you can use the list to
get an idea of the sort of things I’m looking for.

Collaboration policy: Each student will do a different project, since
I want you to think of your circuit as a form of personal expression. However,
people are strongly encouraged to help each other
out, both with bantering around design ideas and
particularly with debugging.
Often, the
mere act of trying to explain what’s on the breadboard to someone else
will cause
you to discover the source of a bug. You can draft people from outside the
class to help you design and debug too. Feel free
solicit advice on online forums (the
SDIY list that I’m going to make you join will be particularly helpful.)
only caveat on all this is that you must
thank the people who aided you
and describe
how they aided you in your report. (Also, don’t be a complete idiot,
i.e. don’t try to con someone online into designing the entire circuit for

Timeline: How about the following tentative timeline:

  • By Sunday, April 13, send me an e-mail about what you want to do
    for your project.
    (If you have absolutely no clue, I’ll try to suggest something, but I’d prefer
    if people picked something they’re enthusiastic about).
    I want to have a
    of projects, so if someone tells me they want to do a project someone has
    picked, I’ll probably suggest they try
    something else (or suggest some additional twist).
    First come, first serve, more or less. Put “EMS project idea” in your e-mail
    so I can easily sort through them. The sooner you get this to me, the
    better; I have an encyclopedic knowledge of obscure synthesizer related
    tidbits (you may have noticed), and I can probably suggest some things to
    look at for you to get a head-start.

  • Depending on your project, it would be a good idea for you to get me
    a draft schematic as soon as possible – you can scan it and e-mail it to me.
    I may put it on a website and post it to the SDIY mailing list to get
    comments and suggestions. If you’re modularizing or modifying an existing
    design, you can print out the schematic and kind of sketch out the changes
    you are planning to make.

  • By Friday, April 18, have something put together on the breadboard.
  • By Friday, April 25, show me something working on the breadboard.
    (Notice I left two
    weeks between “put together” and “working.” Debugging circuits is tricky; it
    requires a detective’s mind! There may be a problem in the hookup on the
    breadboard, or there may be a problem with the underlying design in the
    schematic, and you never know which is the case at first.)

  • By Tuesday, April 29, show me someting put together “in solder,” i.e.
    a piece of hardware we can add to our existing system. This probably won’t
    work immediately, but will need a bit of debugging.

  • By May 2, show me a working module “in solder.”
    can put this together on perfboard or stripboard.
    (If you’re ambitious and want to try putting together an
    actual PC board,
    we can look into getting some boards made. I’d only recommend the latter
    option if
    you already
    happen to familiar with a PCB layout program, since they typically have
    an extremely steep learning curve.)
    If you are using perfboard or stripboard, use
    black wires for ground, red wires for +15 V, and white wires for -15 V. This
    will make it easier to debug later, particularly if I have to repair it at
    some date many years in the future.

In addition to the project, I want a brief user’s manual (in electronic
form, e-mailed to me) explaining
what your module is,
what the
controls do, etc., and a few basic notes about how you came up with the
design, any calculations you made (for instance, to get something
to match the MOTM standards), etc. This should be reasonably slick, i.e. the
text should not be
handwritten, although I will accept scans of hand-drawn schematics. I’d like to
emphasize the word “brief.” I am more interested in PRODUCT
than I am in PROSE.
Do not write something lengthy, since
I will not have time to read it anyway. The user’s manuals will be posted on
an archival website. Many people may build your circuit!

Due date, sort of:
The above timeline is just a guideline to help you gauge your progress;
I won’t be carrying a specific checkoff list.
(However, if you start falling behind these guidelines, you should redouble
your efforts to catch up.)
When is the project due? Well, I will
accept boards and reports up to and including the weekend after finals; I
need to have grades figured out and turned in by noon the following Monday.
My thought is that if you head home during finals week, you can turn in the
board before you leave and then finish the report remotely. However, I strongly
recommend getting as much done as you can the weekend before finals week
so you can focus on studying for your finals.

I again apologize for shifting the schedule so late. My wife and I are slowly
starting to hit an equilibrium in caring for our newborn, and I know that
in a few weeks I’ll be able to be much more available to help than I am now.
(As a side effect, by the time finals week rolls around, ECE4007 will be done
and we will have the lab entirely to ourselves.) I know this is messy. You
don’t have to tell me that on the evaluations. If you insist on complaining
this on the evaluations, I understand, but please add something that indicates
you realized that we just had a baby and that this is an unusual circumstance.

Specifications: Your module should satisfy the MOTM standards
(taken from the MOTM website):

  • 1/4″ jacks for connections (if you look in
    the second-from-top drawer in the
    set of long drawers in the middle of 4007 lab, you’ll find a bunch of jacks)

  • 1 volt-per-octave response for VCOs and filters (you may want to include
    an additional linear input, if appropriate). When running wires to the jacks,
    use black for ground (this will make debugging easier).

  • Positive-going GATE voltages (+1.5 V threshold)
  • Positive-going triggers
  • Audio levels of 10 V peak-to-peak (i.e., -5 V to +5 V)
  • VCAs respond from 0 to +5 volts
  • Use the standard
    MOTM power connectors. There’s two kinds, depending on what you
    need. The modules you built all used a four-pin connector. If the long tab
    is to the
    “right,” then reading from top to bottom, the MOTM power supply gives -15 V DC,
    two ground pins, and +15 V DC. (The MOTM website says these are “standard
    AMP MTA-156 4 position” connectors.)
    If you are using some digital logic (TTL, CMOS, whatever),
    you can use the six-pin connector. The bottom four pins are the same as the
    for the four-pin connector, and the topmost pin gives +5 V DC
    and a “digital ground”
    (so you can try to keep digital switching noise away from
    the “analog” part of your circuit.) The ECE lab staff stock these; ask in
    the stockroom. Note that the connectors don’t fit into the standard
    perf board; the easiest solution seem to be to run some short wires from the
    board to the connector.

You do not need to create a front panel. Just run wires from your board to
your knobs, switches, jacks, LEDs, etc. Let the wires be long enough that I
can rearrange the various elements. (Over the summer, I plan to design a front
panel that includes everyone’s modules, get it professionally made, and then
mount everyone’s circuit in it. If you have your interface components dangling
off the board like an octopus, that will let me rearrange things easily.)


for a list of specialized synth-related parts I have personally stockpiled.
If you want something to
experiment with or put in
your final design, just ask. A lot of more standard
parts, including pots and
TL08x type op amps (which are a good workhorse audio
op amp) are
available form the ECE. If you need some other part that I don’t currently
have, let me know and I’ll see if I can get it.

Tips on jacks:
The jacks we are using allow connections to be “normalled,” which may come
in handy in your design. If you look at the jacks, you will see that ground
is ground, but the signal connection can go to one or two points. When you
plug in a cord, the signal part of the plug will connect to the “signal”
part of the jack. But if you don’t plug anything in, the signal part of
the plug will snap to a “default” connection.

In lab, you can use the various signal generators to provide audio, and you
can use the many speakers hooked to the computers in the lab to listen to
the audio. It is often convenient to clip allegator clips directly to the
jacks themselves to emulate plugging something in.

Your project grade will be based on how impressed I am.

I consider
the project to be the most important thing in the class; hence, your course
grade will max out at whatever your project grade is, e.g., if you do B work
in the exams and homeworks but turn in an A project, you might get an A
for the class,
or you might get a B; but if you do A work on everything else but turn in
B level
project, your grade won’t be an A.