ACMS: Analog Circuits for Music Synthesis
Final Project – Spring 2015
For the project, you will construct an analog synthesizer
module to expand our existing modular
system. You will be allowed to
use existing schematics you find from the web and elsewhere.
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).
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. It would be nice if this was relatively
“original,” in that a modularized version doesn’t already obviously
exist on the web.
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. (The more original a design is, the less strict I will
be about how “polished” the final result is.)
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 consider discussing
sharing a portion of your
with the original sources of your design, if possible.
(As mentioned in class, schematics
but circuits can’t, so if a circuit isn’t patented, you can legally
and sell it however you like – but what’s morally the right thing to do
may be 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
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) even getting a circuit from a published schematic working
can be challenging.
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, in general,
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
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.
mere act of trying to explain what’s on the breadboard to someone else
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
how they aided you in your report. (Also, don’t be dishonest about it,
i.e. don’t try to con someone online into designing an entire circuit for
Timeline: How about the following tentative timeline:
- By Tuesday, March 10, 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 diversity
of projects, so if someone tells me they want to do a project someone has
already picked, I’ll probably suggest they try
something else (or suggest some additional twist).
First come, first serve, more or less. Put “ACMS 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 ideas to
to give you a head-start. I will get together with you and give you whatever
parts you need.
- 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, or just send me a URL to the schematic and describe
the changes you plan to make in an e-mail.
- By Thursday, March 12, have something put together on the breadboard.
- By Tuesday, March 31, show me something working on the breadboard.
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 7, have a PCB layout of your circuit design, a
and a layout of your front panel design finished and ready
- Sometime during the weekend of April 24, 25, or 26 – or preferably
show me a working, soldered module. (You’ll probably discover errors on your
PCB; you may “hack” these however you need to get htem going.)
I know many of will will have other projects due on Friday, April 24,
which is why I think it’s a good idea to
give you the weekend before finals to work on it. This makes sure your finals
week is still spent primarily studying for finals, but also gives you a couple
of days slack time if you need it, i.e. if you have a bunch of other stuff
due on Friday the last week of classes.)
In addition to the project, I want a brief user’s manual (in electronic
form, e-mailed to me) explaining
what your module is,
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. Please include photos of your final
built circuit board. (Including a photo of the breadboarded version would
be nice, but is optional.) Basically, your report should be sufficiently
detailed for someone else to reproduce your work.
This should be reasonably slick, i.e. the
text should not be
handwritten. 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. Please get this to me sometime
during finals week.
Due dates, 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.)
Specifications: Your module should satisfy the MOTM standards
(taken from the MOTM website):
- 1/4″ jacks for connections (I will get a bunch of 1/4″ jacks)
- In general, a 1 volt-per-octave
response for VCOs and filters (you may want to include
an additional linear input, if appropriate). Some filter designs won’t have
a clear exponential control mechanism; don’t feel obligated to try to add one.
- 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. 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 stocks these; ask in
for a partial list
list of specialized synth-related parts I may 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 lab stockroom.
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.
Grading: Your project grade
will be based on how impressed I am.
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.
My general procedure in this class is to push each student until I see what
I consider “A” level work.