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Hardware Hacking Music Build Hardware

Ask Slashdot: Cheap and Fun Audio Hacks? 135

An anonymous reader writes: A few years back I discovered that even a person of limited soldering skills can create a nifty surround-sound system with the magic of a passive matrix decoder system; the results pleased me and continue to, It's certainly not a big and fancy surround system, but I recommend it highly as a project with a high ratio of satisfaction to effort. (Here's one of the many, many tutorials out there on doing it yourself; it's not the long-forgotten one I actually used, but I like this one better.) I like listening to recorded music sometimes just to hear how a particular playback system sounds, not just to hear the music "as intended." I'd like to find some more audio hacks and tricks like this that are cheap, easy, and fun. Bonus points if they can be done with the assistance of a couple of smart children, without boring them too much. I have access to Goodwill and other thrift stores that are usually overflowing with cheap-and-cheerful gear, to match my toy budget. What mods or fixes would be fun to implement? Are there brands or models of turntable I should look for as the easiest with which to tinker? Are there cool easy-entry projects akin to that surround sound system that I could use to improve my radio reception? I'm not sure what's out there, but I'd like to get some cool use out of the closet-and-a-half I've got filled with speakers and other gear that I can't quite bear to toss, since "it still works."
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Ask Slashdot: Cheap and Fun Audio Hacks?

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  • by phantomfive ( 622387 ) on Sunday January 10, 2016 @05:42PM (#51274275) Journal
    It's fairly common, but you didn't mention it, so a simple circuit hooked up to christmas lights can be fun.
    • Flame speakers!!! (Score:4, Interesting)

      by goombah99 ( 560566 ) on Monday January 11, 2016 @11:44AM (#51277899)

      you can use a flame as a speaker. Cool thing is you can't burn it out by overdriving it!

      1) create a large wide flame. e.g. for gas flatten a tube into a long thin jet.
      2) put two electrodes in the flame
      3) boost your audio into the high voltage range. a high voltage transformer can do this.

      Now say "I am the great and powerful oz!" into the microphone.

      4) get really excited and build a redonkulously large version with 6 foot tall pulsating glames and a a kilowatt amplifier.

      • I've never done it but I've always wanted to play with acoustic imaging in heaphones. Clearly a two speaker system has 2 degrees of freedom and therefore cannot have any 3D effects. Yet we know that our ears can tell sounds that come from behind from those that come from ahead. This is because our brains process the sound for a reverb or delayed echo. So you cread the 3D effect by delaying the left ear's sound slightly and feeding it to the right ear.

        that of course is just fake spacial assignment. THer

        • take apart your couch, get a giant subwoofer coil, remove the paper cone, and bolt a large weight to the center instead, and mount the speaker on the couch frame. make sure the cross-over is sub 20Hz so you can't hear it in the audio range (otherwise it will be distracting). for more kicks mount three, one for left, one for right and one for the matrix-center channel. drive it with a lot of amps.

        • by tlhIngan ( 30335 )

          I've never done it but I've always wanted to play with acoustic imaging in heaphones. Clearly a two speaker system has 2 degrees of freedom and therefore cannot have any 3D effects. Yet we know that our ears can tell sounds that come from behind from those that come from ahead. This is because our brains process the sound for a reverb or delayed echo. So you cread the 3D effect by delaying the left ear's sound slightly and feeding it to the right ear.

          that of course is just fake spacial assignment. THere's s

        • by muridae ( 966931 )

          That last degree of freedom is the combination phase and volume. Louder on the right than the left? Must be to the right of the listener. The brain then processes the phase of the soundwave to determine the angle forward or backward, up and down.

          Now, the brain can't use that information alone to determine if some sound came from 45 in front or 45 behind (vision helps that), but height above ground can be approximated by echo and interference. Truthfully, the subconcious 'sound map' of the place you are at a

  • by Anonymous Coward

    Not boosted/normalized audio sliced down to a 128 kbit stream.

    Listen to a decent record from the 70s for inspiration.

    • Re: (Score:2, Interesting)

      by PRMan ( 959735 )
      Input error. There are no decent records from the 70s...
      • Re: (Score:2, Interesting)

        by Anonymous Coward

        Actually, from an audio engineering perspective, this is quite true (at least for vinyl), since all records were run through a low cut filter in order to eliminate rumble/skipping due to low sonic frequencies distrubing the needle in a record groove.

        If we are talking a clean, complete signal, vinyl records have plenty of deficiencies of their own, despire what so-called "audiophiles" might tell you.

        • So your speakers work down to 3hz?

          • Yes, they do. They work perfectly well. You can't hear them, but they work just fine.

            • sealed box speakers drop off 12 db per octave below the resonance. vented/ported/passive radiators drop off 24 db per octave. just what exactly do your speakers look like that they have any response at 3 hz?
        • > Actually, from an audio engineering perspective, this is quite true (at least for vinyl), since all records were run through a low cut filter in order to eliminate rumble/skipping due to low sonic frequencies distrubing the needle in a record groove.

          sub 20 hz would be filtered by the rest of the audio chain (hello psychoacoustic filter on all compressed music), or would end up disturbing the mix anyway. Judging the excursion of the speakers in some badly mastered techno records, i think that vinyl can

          • I skip both vinyl and CDs, and simply go to hear music live. Or play it myself with friends.

            It sounds so real and faithful that way.

        • by sudon't ( 580652 )

          Nice understanding of RIAA equalization you have there! :eyeroll:

        • No, they were cut at somewhere between 20-50 Hz so that you could have enough room for 20-35 minutes of audio per side. The RIAA eq curve was to reduce rumble (and hiss, by boosting the high end), and that was restored upon playback through the dedicated PHONO input of the amplifier. I think this flurry of antique-looking all-in-one turntables is lacking the proper equalization circuit, because they all sound raspy and weak to me.

          That's why 12" singles really do have more punch. With an entire side for u

  • by ClickOnThis ( 137803 ) on Sunday January 10, 2016 @05:51PM (#51274317) Journal

    One of the coolest hacks I have encountered is the use of a computer sound card's audio input(s) to create an oscilloscope.

    Google provides lots of links on the subject.

    • A couple of other posters have mentioned that this project is a very old one. Yes, I understand. I was thinking of it as an educational project for the OP's kids, in the context of his/her offer of "[b]onus points if [it] can be done with the assistance of a couple of smart children, without boring them too much." Of course, that could also mean he wants to employ his kids in the grunt-work for his hobby. I hope it's not just that.

      An oscilloscope can expose a young, smart kid to a whole new understanding of

  • What part of that is a decoder? It's adding more speakers to a 2 channel system.
    It also reduces the output impedance, which increases distortion.

    • It's like Dolby surround. Information for the additional channels is encoded into the original 2 channels.
      You won't get 4 independent channels though, but I think it still counts as an analog decoder.
      More info: https://en.wikipedia.org/wiki/... [wikipedia.org]
    • It's not, it's the old David Hafler/Dynaco circuit. It has interesting effects that mimic something sort of like environmental effects.
        Note that virtually no other scheme replicates nor does the source material contain anything like true spatial effects anyway, they are always synthetic to one degree or another.

      • We were doing this back in the 70s with whatever 2 channel source would handle it plus the added speakers. It's not decoding surround but as it was explained back in the 70s it does give you some cool audio effects from the difference in the stereo channels, IIRC it was phase difference that contributed to the "new" sounds you'd hear. Note: this hack is NOT the reason I no longer have a working Pioneer SX-980,
    • You don't seem to understand the terms decode and encode. They are not unique and new to the digital realm. Audio / Analog encoders and decoders existed before computers. I assure you, this circuit functions as a simple analog decoder.
      • by DewDude ( 537374 )
        Yup. Difference matrix. Been around for years.
        • Yup. Difference matrix. Been around for years.

          i first encountered it in the late seventies, sony had a smallish radio (i don't recall that it had a cassette player; definitely no vinyl playback) which featured a big center speaker and two little side firing speakers that gave a really wide soundstage, and i was so intrigued I had to look at the schematic fo see how it was done; to my then childish mind, it was waaaay out of the box thinking.

          • by DewDude ( 537374 )
            I don't think most people knew what a matrix was, not till the quad era. The earliest reference I can find to it is from 1931, which talked about using hybrid transformers to matrix audio. Most people encountered it in the 60s/70s in the form of FM MPX, also called FM Stereo. The mid/sum channel is used to modulate the main FM carrier; while the difference/side is contained in a dual-sideband carrier supressed amplitude modulated subcarrier at 38khz in. Of course, mid/side matrix is also used in the bulk o
      • You don't seem to understand the terms decode and encode. They are not unique and new to the digital realm. Audio / Analog encoders and decoders existed before computers. I assure you, this circuit functions as a simple analog decoder.

        decode is ib my node.

    • by sjames ( 1099 )

      Look carefully at the polarities.

      • The only difference that's going to make is put the phase of the sound waves out 180 degrees

        • by sjames ( 1099 )

          Not quite, no.The surround channel is encoded as a net differential between the left and right channels.

  • by Anonymous Coward

    Its rather simple to make a basic SONAR system with Matlab/Octave. If you can get enough identical speakers/microphones, you can start building phased arrays and directional microphones.

    USB sound cards generally have less electrical noise, and rather good effective number of bits and sample rates.

  • by Anonymous Coward

    ... I had fun building an ultrasonic microphone to listen to laughing rats, bats etc from a cheap microphone capsule. I think that a lot of small electrets (such as those in hearing aids) have a good response to high frequencies. But there is an investment required in that you need a DA converter with a high sampling response to digitise your recordings. If you have a soundcard with 192kHz inputs, then the rest is pretty cheap, and the circuits can be pretty simple.

    With a bit more investment of time in the

  • Audio? Kinda (Score:3, Interesting)

    by Traciatim ( 1856872 ) on Sunday January 10, 2016 @06:18PM (#51274431)
    Try a singing Tesla coil. Kids will love making music with lightning.
  • There is a lot you can do beyond just audio. Put a low freq wave in a horizontally oriented speaker cone and see how it interacts with eg slimes/liquids. Or a high powered speaker with glass or other solids to see how/when it breaks. Noise cancellation techniques etc are also great and useful to explore at every level of the system. Compounding waves, masking and the idea of when tones become 'information'. Visualizing electric wave forms or even making a lung system in speakers is really cool too.

  • One of those cracked screen phones could be set up to get audio streams off wifi. The Bluegrass radio app gets a bunch of eclectic stations.
  • As you seem to turn your kids into geeks anyway, you could build a cheap Theremin with them and teach them to play the Startrek theme song.

    http://www.instructables.com/i... [instructables.com]
    http://www.thereminworld.com/s... [thereminworld.com]

  • by steveha ( 103154 ) on Sunday January 10, 2016 @06:55PM (#51274617) Homepage

    The O2 headphone amplifier is an extremely clean amp that can drive almost any headphones. It sounds great. Pair it with a clean DAC, rip all your CDs to FLAC, and you can listen to your music from your computer with the very highest in fidelity.

    If you can solder, you can build the O2 amp for $30 to $40 worth of parts.

    http://nwavguy.blogspot.com/2011/08/o2-summary.html [blogspot.com]

    The guy who designed the O2 also designed a really good DAC. He wanted to release it as a DIY project but the realities of the DAC chip business mean that it was only practical to sell a complete DAC board. But you could make a project out of building an O2 amp in an enclosure with the DAC board built-in. (I have such a device but I can't solder; I bought mine from JDS Labs, pre-built.)

    http://nwavguy.blogspot.com/2012/04/odac-released.html [blogspot.com]

    I am friends with a world-class audio expert, and he agrees that the O2+ODAC is the best way to spend your money. It's as clean as $1000+ solutions.

    P.S. Article about the guy who designed the O2 and ODAC: "the audio genius who vanished"

    http://spectrum.ieee.org/geek-life/profiles/nwavguy-the-audio-genius-who-vanished [ieee.org]

  • Make something that will somehow bypass the eardrum/nerve interface so that people like me that have had severe never damage in the inner ear canal can enjoy music again. Who knows where it could go from there but I know I would be eternally grateful!!! Oh yeah, no wires in my brain please!!!

    • I think a cochlear implant will do the job, provided that you still have enough nerve function to hook the device to. It's not cheap, requires professional adjustment after an operation, and the quality is poor. At most you get 22 narrow frequency bands and have to interpolate for intermediate frequencies.

      The technology is improving, but progress isn't particularly rapid.

      • There are brainstem auditory implants that are for people with actual nerve deafness (damage to the 8th cranial nerve, not the cochlea as is the case for most types of deafness)... Since this type of deafness is quite rare (they would only consider something like this for bilateral losses), very few people have them. They are only available via clinical trial in the US for children, but they are approved in Europe.

    • by sudon't ( 580652 )

      "...no wires in my brain please!!!

      Really? I'd love to be able to muck around with wires in my brain, stimulating this part, and that, just to see what happens. I would certainly do it to regain music! But from a practical point of view, I can understand your objection.

  • by lord_mike ( 567148 ) on Sunday January 10, 2016 @07:10PM (#51274707)

    ...but, back in high school, one of my science teachers glued a tiny mirror to the center of a speaker cone. He then reflected a laser off of it onto the wall. When he played music though it, the vibrations made a very cool low cost laser show! Now that lasers are cheap and plentiful, I've always meant to recreate that laser show. One of these decades, I'll get around to it! ;-)

  • by michael_cain ( 66650 ) on Sunday January 10, 2016 @07:14PM (#51274727) Journal
    Dynamic range compression is one of the audio effects I use most often.
    • by sudon't ( 580652 )

      Dynamic range compression is one of the audio effects I use most often.

      You, and every producer/engineer lately.

      • I'm not sure what their reasons are. Mine used to be that I had to deal with various non-trivial levels of background noise -- turn the volume up loud enough to hear the quiet parts over that noise and the loud parts were enough to knock you over. These days, it's more that aging ears have greatly narrowed the spread between loud enough to understand and loud enough to hurt.
        • I'm not sure what their reasons are. Mine used to be that I had to deal with various non-trivial levels of background noise -- turn the volume up loud enough to hear the quiet parts over that noise and the loud parts were enough to knock you over. These days, it's more that aging ears have greatly narrowed the spread between loud enough to understand and loud enough to hurt.

          just add a little high freq distortion and gated white noise. http://www.aphex.com/products/... [aphex.com] in the initial days of solid state audio, everybody was so thrilled with how much better the highs sounded compared to tube amps. then people noticed listener fatigue setting in. then the observations of high freq distortion. then the next generation of much improved amps. then repeat when digital audio becomes a thing.

  • Laser speaker (Score:4, Interesting)

    by wooferhound ( 546132 ) <timNO@SPAMwooferhound.com> on Sunday January 10, 2016 @07:41PM (#51274851) Homepage
    Glue a Front Surface mirror to a woofer
    Point a Laser at the mirror
    Play music with lots of bass through that speaker
    Add a second speaker at an opposing angle to get X Y control
  • Not a hack, per se -- but to do tubes and wrench on 'em yourself pretty much means you're a hacker.

    Hook 'em up to horn speakers and you can get very good sound for not much dosh. Depending on many factors ridiculously good sound is possible, actually, for not much dosh.

    It teaches about electronics. And also teaches basic mechanical skills, what with the screwdriver, wrenches, soldering iron, etc etc -- it's more than just audio.

    No, really -- but be safe, triple-digit VDC will really @#!% you up and there'

    • Vacuum tubes are the best. They saturate with only even-n harmonics, making them sound 'warm' or 'natural', unlike the random things you can do with digital audio streams.

      It's the same idea as the harmonics of a guitar string.

      Look up "Fourier Decomposition of a Wave" on Wikipedia for more details.

    • by Jawnn ( 445279 )

      Not a hack, per se -- but to do tubes and wrench on 'em yourself pretty much means you're a hacker.

      Beat me to it. I built a GainClone amp a few years back, and while it was impressive, something was missing. On the pure hunch that the single ended triode (SET) zealots were actually onto something, I decided to build a Tubelab [tubelab.com] SSE. Best thing I have ever built, bar none. The side-by-side comparison with my chip amp was astounding, even with the cheap Chinese 6L6VG tubes I used while shaking down the new build. The typical SET tube amp is not the best fit for ballz-to-the-wall rock or full symphony materia

      • Not a hack, per se -- but to do tubes and wrench on 'em yourself pretty much means you're a hacker.

        Beat me to it. I built a GainClone amp a few years back, and while it was impressive, something was missing. On the pure hunch that the single ended triode (SET) zealots were actually onto something, I decided to build a Tubelab [tubelab.com] SSE. Best thing I have ever built, bar none. The side-by-side comparison with my chip amp was astounding, even with the cheap Chinese 6L6VG tubes I used while shaking down the new build. The typical SET tube amp is not the best fit for ballz-to-the-wall rock or full symphony material, but Steely Dan, Diana Krall, Nora Jones, or Cowboy Junkies? Yeah, way worth the time.

        you can build fine IC amps, or fine discrete transistor amps, or fine tube amps, or fine digital amps. however, the kinds of errors that occur in imperfect tube amps are less irritating than the kind of errors that occur in imperfect solid state amps, which are less irritating than the kind of errors which occur in imperfect digital amps, as a generalization. which seems to correlate with the prevalence of similar kinds of distortion in "natural" sound, as my halfbaked observation.

  • One of the hacks I always wanted to do ( and still looking for parts for) is a flame speaker. [swtpc.com] I plan to do it outside maybe even in a bonfire if I can keep the wires from melting.
    • One of the hacks I always wanted to do ( and still looking for parts for) is a flame speaker. [swtpc.com] I plan to do it outside maybe even in a bonfire if I can keep the wires from melting.

      you can get plenty of flame speakers on the /. comments.

  • I'm guessing that the quadraphonic decoder you built was some version of the Dynaquad - am I correct? (I actually have a Dynaquad-encoded copy of The Beach Boys album 'Surf's Up'). And I think the link you provided is David Hafler's version of the same basic concept. Either one of these decoders could do fascinating things with even normal stereo recordings. I did a LOT of playing around with passive decoding in the early-to-mid-70's when I was a teenager - I just loved playing Dark Side of the Moon...

    I als

  • by Camembert ( 2891457 ) on Sunday January 10, 2016 @11:06PM (#51275671)
    My suggestion is not super cheap at $589 yet very satisfying: an Elekit tube amplifier kit. Elekit is a good japanese kit brand and their tube amp kits are very well regarded. In fact a similar quality ready made product would cost a lot more.
    Here is the link to the importer in Canada who delivers to the Americas. He supplies the construction manual in English, this is I think not the case if you buy straight from the japanese Elekit website: http://www.vkmusic.ca/TU-879S.... [vkmusic.ca]
  • by russbutton ( 675993 ) <russ@NOsPAm.russbutton.com> on Monday January 11, 2016 @04:09AM (#51276417) Homepage

    I've got a friend who's a cabinet maker and loudspeaker designer. For years he crafted full-range curved diaphram electrostatic loudspeakers. Nowadays he's into horns. One day I dropped by his shop and he blew me away with something he'd been doing with Dayton Audio Sound Exciters (well, that's what they're called today on Amazon's web site). They're transducers.

    Get yourself two 2' x 3' pieces of 1/2" thick piece of foam core from an art supply store. Attach two of these Dayton Audio Sound Exciters to each of them. Wire them in parallel and connect them to an amplifier. The tricky part is that you have to suspend them in mid-air. Hang them from your ceiling or something. The sound you'll get out of them is very, very good - especially considering you'll have less than $75 in the whole project. I'd put it equal stuff you'd spend about $1000 to $1500 at Best Buy.

    They aren't what I'd call extreme hi-end, but they sound much, much better than anyone would think. Would make for a great garage or shop system.

    • Yeah, electrostatic is the holy grail of audiophiles yet it's a pretty accessible hobby if you have the tools, take a look into DIY Electrostatic Headphones:

      http://www.head-fi.org/t/49829... [head-fi.org]

      Where entry level orthos/isos are in the range of $100 they can get as high as $3000 so not only your kids can wear what they have created, maybe they can start a local "business" Are they worth that much money? IDK I have some vintage Fostex monitors and yes the electrostatic technology is as good as it gets for a
      • I've been an audiophile since Nixon was president. At one time or another I've owned most all of the different technologies in loudspeakers - horns, dome diaphrams, satellite/sub-woofer combo, magnetic planar, electrostatics and now, open baffle. Stats are wonderful, but have their issues. Flat panet stats and magnetics both have awful high frequency dispersion. You have to sit in the sweet spot. Stand up and the high end disappears and they sound like an AM radio. Walk around the room and you have th
  • Sorry to go slightly off-topic; I sometimes envy those that can enjoy music for sustained periods of time. Listening, even to my favourite music (renaissance and baroque lute), makes my feel stressed out after a short while. However, there is one project I would like to accomplish - but it's hardly for beginners, I suspect.

    I have a large conservatory in which I grow orchids, mostly. One of the problems you get in a space enclosed in glass is that important parameters like temperature, humidity and air move

  • by Anonymous Coward

    "Hacking" sounds illegal and in this day and age, if something just sounds illegal it probably is, and it's best to err on the safe of caution. You should not alter equipment or modify it, you can only use as specified in the contract. Buy something that meets your criteria and be content with it. If nothing in the market can meet your criteria, then probably there's something wrong with you.

    • by sh00z ( 206503 )

      "Hacking" sounds illegal and in this day and age, if something just sounds illegal it probably is, and it's best to err on the safe of caution. You should not alter equipment or modify it, you can only use as specified in the contract. Buy something that meets your criteria and be content with it. If nothing in the market can meet your criteria, then probably there's something wrong with you.

      Seriously? Wow. One egregious error per sentence.

      1. 1. I can pretty much guarantee that any "hacking" that the OP undertakes will be in the analog domain, and not subject to the DMCA.
      2. 2. I've never seen a EULA on a piece of audio equipment, even a Blu-Ray player with HDMI. You're not signing a contract.
      3. 3. The OP is looking for a project, a hobby. His hobby is apparently *not* shopping.
      4. 4. If you think Audio is a "one size fits all" proposition, then there's something wrong with YOU,

      So, back to the origi

  • You can make a fun spike mic to listen to people in another room with old parts.

    Take an old phono cartridge and carefully attach a metal nail to the tiny stylus end (where the diamond is).
    Then plug it into an old phono amp as usual, and listen with headphones.
    If you drill a hole on your side of the wall, big enough so the nail doesn't touch the edges, but lightly presses against the wall of the next room, you might be able to hear what's going on.
    (Don't use this illegally!)

  • http://www.openmusiclabs.com/p... [openmusiclabs.com]
    Useful and you couldn't get simpler.

    Whether you want to bring your kids to loud concerts is another story though.

  • Around Thanksgiving, the Linux Voice podcast had a "find of the fortnight" about a small, cheap Bluetooth 4.0 module that can easily be added to an existing system. The card is designated KRC 86B, and a raw board is about $10. As a raw board, there is programming in place that handles everything you need to send audio from your phone and the board has audio in and out all configured. I think they are the same ones that are used for Bluetooth connections in new cars these days.

    Bare boards have soldering

  • I recall there was an article many years ago that mentioned how to use an extra set of speakers adjacent to the main speakers to eliminate audio crosstalk similar to vintage Polk SDA speakers and Carver Sonic Holography, I don't remember the wiring diagram but it used the same amplifier as the main speakers with the additional speakers wired in series and out of phase. The ideal listening position was fairly narrow and the results were hit and miss depending on the recording. Maybe an old Polk SDA review
  • Lots of people do equalization, but mostly just by ear. Tools to use SCIENCE to do it are now cheaply available.

    1) play music out of your computer with an equalizer. I use Foobar2000. There is a free 31-band stereo equalizer plug in available for it. http://www.foobar2000.org/comp... [foobar2000.org]

    2) play some Pink Noise through it. Pink Noise is equal energy per octave, so on a log frequency graph of SPL it should be flat. Of course, it won't be b/c speakers and rooms are imperfect, but now you have a goal. Downlo

  • Guitar distortion pedals can be a cheap and easy thing to build. The simplest form is just an amp (either op-amp or single transistor) followed by clipping diodes. One potentiometer to control the voltage out of the amp stage (higher voltage means the diodes clip more, means more distortion) and another controls the output volume by dropping the signal to ground. And if the kids are the ones playing the instruments, they might enjoy the different effects that can be gained by just using one diode, or mismat

    • Guitar distortion pedals can be a cheap and easy thing to build. The simplest form is just an amp (either op-amp or single transistor) followed by clipping diodes. One potentiometer to control the voltage out of the amp stage (higher voltage means the diodes clip more, means more distortion) and another controls the output volume by dropping the signal to ground. And if the kids are the ones playing the instruments, they might enjoy the different effects that can be gained by just using one diode, or mismatching them (silicon one way, germanium the other). Any instrument can be run through a homemade one, even a microphone if someone plays non-electric instruments.

      i used to fool around with that stuff, more from the electronic standpoint than the musician, so caveats. anyway, you could do some fun effects by using an opamp with a power supply that supplied too low a voltage. and/or for an amp that required positive and negative supplies relative to ground, providing asymmetric voltages.
      fun with clipping!

  • with a simple ac power cord from an old lamp, you can demonstrate that pickles fluoresce when 110 volts is applied to the ends. and as a bonus, the same setup cooks hot dogs efficiently.

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