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  • Making noise

    SO when I was a kid, transistors were a new thing. I'd read Popular Electronics and similar hobby electronics magazines. A common build-it article for a transistor was the "code practice oscillator." Ham radio was still a big deal then, and learning morse code was required. SO people were always coming up with dumb little circuits that went beep when the switch was closed. SO making noise was kind of a passtime.

    I found various silly ways to do it. When you are a kid, you try things you might not when older. What possessed me, I'll never know, but one day I took a small electric motor, like from a toy and connected it to a battery to make it spin, then for some reason I wired a speaker in series with it. Just a cheap brush type motor, we didn't have brushless ones then. What a noise. Kinda like holding a power drill right next to your guitar pickup. Forbidden Planet being a cool film of the day, we imagined it sounded a little like the Krell monster.


    My favorite thing was a relaxation oscillator. Imagine a B+ voltage. I think I was using 90v, but it doesn;t matter really. Put a resistor and neon lamp in series, with a cap across the lamp. MAke the resistor large, like 1 meg, and use a reasonably large cap. Do the math for the RC time constant. The cap charges up over a few seconds. The neon lamp in parallel with the cap won;t fire until the voltage across it reaches its firing voltage - 60v maybe? So the cap charges up until it gets to the neon lamp firing voltage. The lamp strikes, discharging the cap, and the cycle repeats. I had a bag of hundreds of 1 meg resistors at the time, so I left that constant and varied the cap. Large cap, slow oscillation. Vup, vup, vup. Smaller cap, faster, even into audio. You can watch the bulb blink, or at fster speeds it just glows. So clip a coupling cap on it and feed this signal to an amplifier. Hear the oscillation. I made more R/C/Neon circuits and paralleled them on the power source. It wasn't well regulated, so they interacted. The one would be a second or so, while the other would be a few hundrd Hz. The audio one would slowly ramp up in freq until the other one fired. SO the whole thing went up and down in a cycle like a police siren. Well, more like a sweep generator. One could also connect one RC to the junction of another. There were various ways to interconnect them. I managed to get a sound like a sweep generator of a set range while the base freq slowly rose then reset. A swept sweep, as it were. All with a 90v battery supply, a bunch of 1 meg resistors and a pile of miscellaneous caps.

    And when I got into building amps, I was always connecting this to that to make them oscillate.

    My sister really hated when I;d feed noises into the phone wiring while she yakked with her friends. And mom hated noise of any kind, telling down the stairs "Stop whatever it is you are doing... NOW."
    Education is what you're left with after you have forgotten what you have learned.

  • #2
    I didn't start doing electronics until I was in my twenties. So my family was spared having oscillators attached to the phone line (loved that). But from the age of 12 forward I did make an awful lot of noise with my guitars and amps! I was always trying something strange and non musical. Like plugging the effects send on my Peavey Bandit 65 into my RAT box and then back into the amps input. Instant square wave oscillator with the RAT box control knobs allowing some sweep function. Or I might spend a whole afternoon playing my guitar with a retractable antenna. Alternately slapping and sliding on the strings.

    Snakes and snails and puppy dogs tails
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #3
      Enzo,
      Your relaxation oscillator story reminded me of another project from back in the day.
      It was a box of neon bulb relaxation oscillators with the bulbs mounted on a panel where you could see them blink. The time constant was set to one to two seconds and the effect of the randomly blinking lights was quite mesmerizing. Back then, when the highest tech electronic item in the house was a TV that received only a hand full of channels, people thought it was quite interesting. Especially since it ran continuously for years on the internal 90V "B" battery and thus was cordless appearing to have no known power source.
      Regards,
      Tom

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      • #4
        People just can't keep their hands off stuff. I never built it, but I recall an article in one of the magazines - a trap box. There was this box, and in it was a latching circuit and a sonalert. There was a big button on the top of the box, and a label by it that said, "DO NOT PRESS BUTTON". Of course to the idiots who rumaged around in one's shop, that was an open invitation to... press the button. It turned on the sonalert - which, if you are not familiar with them, is a LOUD piezo alert siren. Think smoke detector sound on steroids. But the latching circuit kept it on. The box was battery powered, and there was no power switch. It would sit there continuously making huge noise.

        The only way to turn off this thing was to know the small hole on the bottom was access for a pencil. You pushed a pencil up the hole and pushed an OFF switch. Unless they threw it against the wall and shattered it.
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          Speak of the Devil !!!
          I was around 15 and my Mother regularly searched my drawers when I was away trying to find forbidden stuff, such as cigarettes , a random "Playboy" issue, stuff like that.
          I was sure she did that, because I found things disarranged, but she denied everything.
          Until I also built an impossible to turn off beep box, which had a bottom microswitch, which when released triggered an SCR (C106D).
          Pressing it again was useless; once triggered you had to open the box and either pull the battery or short the SCR.
          Imagine my pleasure when I arrived from School one day and she was red-faced saying "don't know what happened, I was dusting that piece of furniture and some d*mn*d beep started sounding, turn it off".
          Oh well.
          Juan Manuel Fahey

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          • #6
            Life is long and hard, but once in a while we win one.
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              I love the "mother alarm".

              When I was at uni, my friends and I chipped in to buy a bag of 500 electrolytics seconds. Most were perfectly usable for our projects. Many just had printing problems. Some had no labels at all. The new (then, now demolished!) student flats had a 5A trip in each bedroom to stop us using kettles or worse. We have 240V mains so that was plenty really in those pre personal computer days. Enough for a bedside light and a radio. The power switched on with the light. It struggled with my mobile disco in there and had to be bypassed. After much thinking about what we could do with the unlabelled caps, a plan was hatched. We sneaked into other students rooms and wired a cap across the mains. When they returned, they would be met with a very loud bang and a puff of smoke, a dark brown smell and the lights would go off. As the resident electronics boffins, one of us would get called to assist. We would just reset the trip and all was back to normal. And the cap? Usually there was no trace of it!

              Don't try this at home!

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              • #8
                I built an equalizer with active butterworth filters while I was in high school in the early 70s. I got it working and decided to plug it intomy band's PA system at 3:00am. We had pretty large system for the time. Several hundred watts in the back room of my older friend's rented house. It sounded like a jet taking off, woke up the entire neighborhood and summoned the police.

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                • #9
                  I was a favorite in my dorm room for using my DOD analog delay

                  and my Yamaha 112 SS amp to do a "spaceship taking off" with the repeat and delay knobs, very much like EVH in "Eruption" It was best with the amp face down on the floor!

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                  • #10
                    In the same house my older friend had a girlfriend with a cat. I didn't care much for the girlfriend (standard band drama) and I hated the cat. So...I tinned the ends of a lamp cord and stuck them in a shrimp. When the cat bit into the shrimp I plugged the power cord into the wall. The result was a bit like flying a kite. The cat finally got away and ran inside of an old Altec A7 cab (we had 6 of them which was why the equalizer malfunction was so loud). It stayed there 2 days and we had to remove the back to get it out. The cat didn't die but from then on had a hair lip. It no longer made the constant noise that bothered me. We called it Meuff. Because it could no longer meow. And...you couldn't force it to eat shrimp again. Yeah, you do stupid shit when you're 17.

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                    • #11
                      My personal preference would be to refrain from spreading information like that cat story on this forum. Don't want to give anyone ideas even though there is plenty of poo to be found on the internet already.
                      Regards,
                      Tom

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