Air Microphones

In DIY audio we made air microphones by soldering a 9 volt battery connector to a resistor, capacitor, and two female 1/8th inch connectors. We connected the microphone piece to one of the female connectors and then connected our miniature amplifiers to the other. The air microphone creates an electrical signal when the small diaphragm in the microphone piece is moved back and forth. These movements are created by the vibrations in the air otherwise known as sound. Air vibrations are known as compressions and rarefactions. The nine volt battery, resistor, and capacitor amplified the signal sent by the air microphone. This microphone was surprisingly effective and inexpensive. These microphones are easy to make and are also very compact. It would be easy to hide these microphones in a space for an installation or performance.

The Final Failure

Advice to future DIYers: Don't drink a pot of coffee before you begin soldering your final project together. I usually pride myself on my soldering skills, but I'm usually not shaking due to copious caffeine consumption. Truthfully, I never figured out what went wrong with my final project. It was basically the circuit I outlined below (see "Recipe for my favorite oscillator") but I think something went wrong with the amplification area of the circuit. I thought it might be some problem with solder dots touching, but as I tried to clean it up, I made the connections progressively worse and eventually connected 5 pins of my 14093 to each other with a big blob of solder. After scraping the connections clear with a knife my circuit buzzes quietly; a pale shadow of its former self. I'll try to salvage it sometime, I don't like the idea of wasting such a wonderful chip.

Anyway, it's been an enlightening journey in DIY class. I learned a lot about electricity and sound. I got to listen to my hair. I will forever treasure my radio-shack mini-amp and the assortment of tiny electrical components which currently litter my carpet. I still think the class needs more enameled copper coils though. Many thanks to Dr. Twombly and my classmates. Have a safe and productive summer everyone!

Amp Chip 386N

Tiny and useful. Cut out the middleman! This circuit should be pushed back earlier in the semester. Once we built it I was able to apply my chips to the happy task of oscillating all the random speakers that are scattered around my room. No more restrictive mini-amp. Better yet, you can build the 200-gain variation and listen to the distortion as your speaker attempts to cope with the ridiculous amount of power. And it uses one less battery than the typical mini-amp setup. This was a vital piece of my final project (and sadly the source of its failure) but after I dig it out of the circuit board I'm sure I'll be using it again.

I assume if you made a fancy little case for a circuit like this you could undercut radio-shack by selling the things for 10 bucks on ebay.

That Amplitude Follower / Gate Thingy

By far the most complicated circuit we built in class. I understand the uses it might have but in my opinion the returns don't warrant the effort. Other than making mp3 players sputter with oscillator controlled volume it doesn't seem to serve much purpose. I mean, the lights are pretty and all, but I want my circuits to generate sounds not follow them. I suppose if you were building a stereo it would be a useful indicator of volume, but I don't frequently build stereos. And what happened to our class playtime? That's the best part! Another note to Twombly: Don't cut out playtime. Also, get some of those frequency divider chips next time around, simpler and way cooler than amp tracking.


Hmmm... now that I think about it though, it might be interesting to modulate the amplitude of one oscillator with another oscillator. Perhaps a summer project?

Guitar Pickups

Our Guitar Pickups combine two of my favorite things: Powerful magnets, and copper coils. I don't quite understand how a magnet that is glued into the center of the spool can vibrate enough to induce a current. But it does, and I guess that's all I really need to know. My guitar was a soprano as I could only find a two foot stick. Fun but tragically limited to the fundamental and harmonics by the single string setup. Frets would be useful. I thought it might be fun to pair a series of pickups to a few strings, but I found out someone beat me to it already. I briefly experimented with trying to pickup signals from other things, but results were similar to a poorly constructed telephone pickup.

I'm much more interested in building the inverse of a pickup: a speaker. Note to Twombly: consider adding a speaker assembly day, there was a disappointing lack of copper coils this semester. Better yet, build the amp circuit and a speaker early on and we can use homemade speakers on the other projects.

The Fourteen-o-Nine-Three!

Finally! Clean, pure, digital, clarity. My radio-shack mini amp hums and bleeps with modulated magnificence.

Recipe for my favorite oscillator:

Input 1: +, Input 2: cap 47uf to -, Output 1: Route to Input 3, Input 4: cap 4.7uf to -, Output 2: Route to Input 5, Input 6: 2.2uf to -, Gound pin 7 and hook pin 14 to positive. Put some pots between even numbered inputs and their relative outputs and listen to the difference between Output 3 and ground.

Best chip ever. It provides countless hours of entertainment and a clean form of modulation between oscillators. Hook it up to a guitar amplifier and play around with reverb and wah-wah effects. Hook it up to the amplitude gate and make your favorite tunes throb with intensity. Hook it up to a subwoofer and shake the dust off your furniture. Add some LEDs and you've got a festive Christmas decoration. Connect it to the pickup coil and broadcast your signal into the aether. Matrix two of them and you have eight oscillators at your fingertips. Run jumper cables between random points and observe results. Limitless potential!

The Hex Schmitt Trigger aka 74C14

Bad integrated circuit! Very bad! Your oscillators fail to maintain independence from one another! Bad! I've never liked this chip. Six oscillators sounds like a great deal, until you realize that they all leak into each other and form an ugly jumble of sounds. I attempted to use a series of diodes and resistors detailed in the textbook to separate them; still an ugly jumble. Some people might enjoy ugly jumbles, I do not. Synthesized sounds should be clean and pure, or dirty with intermittent bits of purity, or clean with bits of impurity, but never ugly jumbles. The only way to isolate the signals is to use an amplifier for each one. Who can afford that many batteries? You can get one good oscillator out of this thing. Don't try any more because it will sound like an ugly jumble. I suppose this is the downside to using circuitry that was never intended for sound applications. I guess it's possible I wired it incorrectly, or I have a bad chip; but the 14093 is so much more awesome that I don't even want to look at a Hex Schmitt again.

Childhood Distortions

Who doesn't love to hack the toys? I fondly recall the drunken ramblings of my Leapfrog Phonics Teacher as she lethargically inquired if I could spell "cat" whilst the inner workings of her brain were being subjected to ungodly abuses at my hands. Curse her surface mounted resistors! I was never able to wire in a potentiometer, so satisfied myself by removing components until her voice became indistinguishable. Can you spell: spare parts?

I had better luck with the nameless pan-cultural child depicted on the front of my Playschool cellular phone. At least he was kind enough to show an interest in whatever I was doing that day. His circuits were large enough to allow variable resistor control. Useful for speeding up dull conversations.

Experiments with voltage starving (suggested by the textbook) were ineffective for both of these toys. I think it'd be more interesting to tamper with a less "scripted" toy such as a keyboard. If you watched the DVD that came with our book then you saw the Casio circuit beneath the ornamental waterfall. Awesome.

The Electret Microphone

My knowledge of Electret Microphones is limited, even after an extended visit to Wikipedia I still don't know much about them. Apparently, electret microphones have a permanent static charge stored inside a dielectric material, this removes the need for phantom power to the capacitor which is required in traditional condenser microphones. You still need a powered preamplifier though. They make them by melting plastic in an electric field or something. It seems the main advantage of the electret mic is its cheap production cost. Wiki says your cellphones and computers probably use them, and over 1 billion are produced every year.

I'll be honest, I'm not a big fan of microphones. In my opinion sound synthesis is so much cooler than sound reproduction. Granted you can probably find some way to take the output of the microphone and alter it (say filtration via aforementioned contact mic), but I'd rather spend my time with the mathematical purity of integrated circuit oscillators. Mmmmm....integrated circuit oscillators. I also find it rather annoying that getting this thing to make audible sound requires an additional 9 volt battery. I don't have the money to support such lavish power needs. I'd rather save my cash and listen to my hair with the contact mic.

Contact Mics!

Piezoelectricity! What a word. It's the primary component of the so called "contact microphone." Tiny fluctuations within the piezoelectric disk transform manual force into voltage. I love these things. They're like magnifying glasses for your ears. How often have you wanted to listen to the sound of your individual strands of hair, only to be hampered by your pitiful human ears? Now you can! Compare the sounds of fabrics like wool, cotton, and polyester. Hear the dull thud of rocks falling on two by fours. Or revel in the glory of the plucked spring! Beware or pursue the feedback loops created when speaker and mic are in contact with the same object.

Interesting filter effects can be obtained using two contact microphones transmitting vibrations across a material; spring, metal, plastic, wood, anything rigid will do. Attach them to conventional instruments like tubas or flutes and observe results. It's too bad the tiny wires attached to my disk broke off, or I would be listening intently to sounds of my keyboard right now.

DIY: Early Endeavors

OK, I realize writing all ten posts on the last day possible is probably not the best approach to this assignment. That said, let's just pretend I haven't been procrastinating all semester and think back to those first magical days of DIY.

The Speaker and the 9 volt battery:

Oh how I love the simple principles of electromagnetism which control our modern speakers. Succinctly put: a tiny copper coil, wrapped around a paper cylinder, and suspended in a permanent magnetic field. Electrify the coil, and the wonders of nature shall bestow magnetism upon the coil, causing it to be repelled or attracted to field the permanent magnet. We exploited this property early in class by interfering with the circuit; include a semi-conductive material (such as rusted metal or graphite) and drag the contact across it. Your ears will be treated to a satisfying series of pops and snaps as the current struggles to complete itself. Paperclips connected to opposite ends of the circuit and placed within the speaker cone create an unusual feedback device; as the speaker cone vibrates, it alternates between completing and breaking the circuit. If adjusted appropriately, this kind of circuit can almost produce a sound vaguely reminiscent of an actual frequency. Astounding! Other ideas? Toss in some random pieces of metal; screws, nails, coins, broken glass, etc. Cut/rip/punch large holes in the speaker cone and observe results. Or submerge your speaker in water and see how long it lasts (after about 10 minutes my cone became quite soggy and would generate delicious sputtering sounds as it died). After you are finished abusing your speaker, hook it up to a stereo system and check to see if popular music sounds any better. If so, immediately patent your design.

The Final Blogtier

To be honest, I am not sure how to wrap up with my final blog. Do I discuss the skills I have learned? I could. My soldering is better as is my confidence in dealing with circuitry but such truths are trivial and do not make good reading of any kind. Do I talk about circuit bending? Been there, done that. Do I talk about homemade instruments? Same shit, different day. What's left? It's the end of the semester and I'm blown out physically and mentally. To borrow a phrase from Dylan, I'm tangled up in blue.
What is left? How about using MIDI to control telsa coils? Not exactly DIY stuff but I think that can be forgiven (it still falls into the electro-acoustic music after all). Bah, that is old hat too. You know maybe I have nothing left to say about DIY. May be I have things to ask instead. This question is open to anyone. This DIY stuff is entertaining on its own and to be a part of but I have to wonder and ask - do you think you will continue to tinker after this class is done? I surely hope to. In fact, I have a few projects in mind for summer. But this is not about me - I would like to hear if anyone else plans on using this stuff in the future.

Toy Tweaking

If youtube is any indication (no I'm not going to post a crappy video with this blog), toy tweaking seems to be a common interest among DIYers in this day and age. Personally, I do not get the fascination as much as others. Sure, toys squeak and squeal, they make hundreds of noises great and small yet in the end they are just noise making circuits. That is all and no different than a home built oscillator or contact mic or some other homemade way of making sound. I guess part of it is ease, why build the circuit when you can buy it made cheap, and part of it, I think, is we respect our own projects too much to bust them up. Part of it might be too the evil enjoyment of making something that is made to be entertaining to children (but annoying to adults) and tweaking it to make horrible noise.
All this is not to say that I do not enjoy circuit bending at all. In fact, one of my favorite things to do that I learned in this class is to bend a circuit using just my hands. There is something about taking a thing that is supposed to be artificially controlled and messing with it in such an organic way. No, I quite enjoy circuit bending. I just do not enjoy tweaking toys as some others. No specific reason. I enjoy doing it as much as tweaking other circuits and may be that is it. I do not see it different than any other circuit while others may put some value to it.

Some people are too good for their own good.

With the last couple of blogs so focused on circuit bending, art installations, and electronic projects I thought I would explore the other side of what DIY audio means for a little bit. That is things that do not plug in or require power or circuitry to work. Apparently, these kinds of instruments are big in the folk scene which I did not know before. It makes sense as folk traditions have often been linked to lower socioeconomic statuses than the rich and homemade instruments must have been commonplace in desolate economic times in the past such as the depression.

This guy has a few acoustic DIY projects that caught my interest. Honestly, the propane tank drum nor the upright washtub-esqe bass are all that interesting (they are common enough projects) but that third instrument caught my eye. A hand cranked fiddle is truly a bizarre wonder and I still am trying to wrap my mind around it. Unfortunately, no plans are listed in the video comments and no discussion on these instruments are made but I will see with a little google fu you can find this information.

PVC pipe drums are nothing new. Hell, the Blue Man Group made a career out of using them. Yet, they seem to be a common instrument among DIYers. I guess, short of trashcans, there is no quicker and easy way to cobble together some drums. And PVC at least allows for variable pitch from some analogy non-circuit bending.

Dr. Twombly Is Going To Hate This Blog (Progressive rock ahead)

I am guessing that blogging about progressive rock in a DIY audio class is going to seem like trying to pick up a hooker outside of Saint Paul's Cathedral to some. This can only be sacrilege of the highest order - worthy of the death penalty or a really nasty stomach flu. Yes, I am bound to make at least one enemy today (Please don't fail me) but as bizarre as it seems circuit bending as a long and strong tradition in the progressive rock world.
The first Moogs were rolling out just about the time progressive bands started to hit it big. Progressive rock bands were known for their musical experimentation and it seemed every would be Wakeman or Emerson got his greedy hands on a Moog as fast as possible. What they failed to see however is that the Moog is not played - it is defeated in mortal combat. The true virtuosos were forced to create their own sounds through complex networks of cables that crossed, shorted out, or elongated the various audio ports on the front. When that no longer survived to create the sound the musician often went to the back of the instrument itself and with a licked finger or a tight grip bent, broke and modified circuits by any means necessary. After all, all was slave to the song. There are a few great videos listed below and, for the sake of the sanity of some, I have listed the time the circuit bending begins to save viewing time.

Keith Emerson playing a Moog with an insane amount of cables patched in it. Watch as he modifies the sound on the fly by changing the network of the cables. (1:40)

Keith Emerson (again) directly messing with the circuits on the back of his synth. (6:05)