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A project log for Hacking Nature’s Musicians

An artistic ecosystem of analog electronic sound generators

Kelly HeatonKelly Heaton 10/28/2018 at 00:292 Comments

I continue to explore circuits for bird song generation. I'm working my way through various schematics found on the Internet, testing them to hear how different parts and configurations sound. So far, most of the bird circuits I've built fall into the "chirping canary" or "depressive parrot" categories. Just prior to this log, I discovered another schematic to try -- and it's accompanied by a really helpful video by Mario Burriel Valencia aka @DJ Mystic  https://youtu.be/W69VaPoPoVo

@DJ Mystic confirms what I have long suspected -- it's not only the shape of a waveform (sine, square, triangle, sawtooth, etc), or the component type (resistor, capacitor, transistor, etc), but the *specific make* of a component that can affect pitch, timbre, and loudness. This is especially true for transistors, and I have also seen variation in capacitors. ...Yes... I have read blogs by audiophiles discussing the pros and cons of specific parts for hi-fi equipment, but I didn't fully appreciate the importance of component specificity in low-cost sound generation. For some reason I assumed that since I work with cheap parts, the make wasn't that important. For example, I have thus-far thrown 2N3904 transistors at every problem they will solve. Now I realize the power of expanding my palette. Fortunately, I've got a friend coming down from the US and she's willing to bring a bag of electronics with her... so stay tuned for that excitement.

As for progress in the past few days, I bit the bullet and breadboarded a circuit with op amps. My attitude may seem weird considering that most synthesizer enthusiasts live and breathe op amps... but the dual power supply annoys me (and I've never gotten interesting effects with single-supply op amps). Fortunately, some years ago, Bernie Hutchins gave me a useful schematic to convert voltage from a DC supply into a negative voltage of almost (not quite) the same magnitude. If you have a 12 volt supply, you can produce negative 9-10 volts using a 555 timer and a handful of components. Please see my files for this handy "Negative supply" circuit or read about it on Electronotes.

The bird circuit that I built with op amps is described as "two canaries singing in a cage." You can find the schematic here: http://circuitos-de-electronica.blogspot.com/2007/10/canary-sound-simulator.html

I substituted a bunch of LM741s for the LM324s because I don't like building in tight quarters. You can see the resulting circuit in this video, where the "two canaries" are in the breadboard in the foreground (a previously built "transformer canary" is in the background):

I added some photocell resistors plus a few wires that you'll see me moving around (poor man's patch synth) to get variation in the circuit's behavior. It's pretty interesting, but maybe not worth the effort because there's a fair amount of complexity for sound effects that can be achieved with fewer parts. Still, I might make one of my electronic painting / sound studies with it because I like the aesthetic of crazy-complicated circuits.

Last but not least, here's a short video of a different bird circuit (the transformer one discussed in my previous log and shown in the background of the "two canary" video). I tested various capacitors and it's pretty cool the realistic bird sounds that you can achieve with such a simple component swap.

Still lots of work to be done.

Discussions

DJ Mystic wrote 11/08/2018 at 21:18 point

Hi Kelly, thanks for mentioning me in your post. I've just realized that there is a small mistake at the schematic shown in my video. When i was drawing the circuit, I forgot to flip upside down the symbol of Q5, hence C and E should be swapped as in a typical Class B amp (the breadboard setup was right). The funny thing is that even if you build it up as it's shown right there, you won't notice such mistake because the PNP type that i used has a very high reverse gain, more than 100 HFE, so it would work fine both direct and reverse connected (with C and E swapped).  Just uploaded a short video to show that https://youtu.be/h2xOw7Lc2Vw

I'm expectant of your research progress. Good job!!

P.S: I thought that the 741 was an obsolete part, but i'm rather surprised people still use it. Eventhough I find such other oldies like NE5532 or TL072 in a regular basiswhen I repair or upgrade a recent purchased audio appliance like a power amp or a mixer table.

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Kelly Heaton wrote 11/10/2018 at 15:33 point

Thanks for your update! I’ve been delayed in my hacking because I painted a mural in Akumal pueblo (you can check that out on my blog on www.kellyheatonstudio.com). Now, I’ve lost Internet in the jungle and can only check messages from a public space when I hitch a ride to town — life on the fringe of civilization :-) I did build your circuit once and didn’t have all the right parts, so it functioned sort of like a VCO but without chirping. I plan to try again in the next few days as will take note of your corrections. Thanks! Ciao

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