Funktionality of analog synthersizers - a few questions

  • Hello EE-Community,

    i plan doing a presentation on analog sound synthesis for physics class (grade 13 in Germany ;D ).
    A few years ago i started to experiment with synthesizers which led to buying a Bass Station Synth....had to sell it last year unfortunately...

    In physics classed we discussed the topic of RLC-circuits for quite a while, but i still have some questions concerning the functionality of a VCO-unit. I hope someone can help me out.
    Thanks in advance!

    Are those RLC-units actually used in common synthesizers? A book i read makes me doubt that, but i couldn't figure it out.....the following images will explain....

    We discussed this RLC-circuit which is an Armstrong/Meissner-Oscillator an can be used to create a sine tone with variable frequency altering inductance or capacitance.

    In the VCO-Chapter of a book about analog synthesizers the oscillator unit is described not as an RLC-circuit but as shown on the picture above.
    a capacitor is charged until its voltage is just a high as a certain reference voltage. The capacitor then gets short-circuited and the charging begins anew.
    This process creates obviously a sawtooth-waveform

    The thing that confuses me, is that the author describes how the above created circuit is used in most modern synthesizers. According to him even synthesizers with a sine-oscillator just modulate and bend a triangle or sawtooth waveform into a sine.
    Why don't they use an RLC-circuit? Is it unstable for musical use?

    greetings from Germany

  • I've never built an oscillator like the one in the diagram (but then I have only ever built a few oscillators). I've never used an inductor coil in any of the synthesizer circuits I built, but that's not to say it can't be done. I'd personally recommend signing up with and asking in the DIY forums (scroll past the sub-forums). There are some really helpful guys there with a wealth of knowledge.

  • LektroiD, thanks for the advise to the forum.
    when you built an oscillator, which type was it?

    Quote from drschmidt;32756

    Hast du Physik als Leistungskurs?

    So ähnlich, heute nennt mans Kernfach (etwas entschärft ;D ) aber das ändert sich alle paar Jahre sowieso.
    Hast du ne Idee, wie gebräuchlich Schwingkreise in "normalen" Analogsynthies sind?

    [sorry to the others for writing in German]

  • Hello
    I found your thread by google search for Meissner Oscillator.
    There was an image there that you have posted here.
    So I was going to suggest this because you would have an easy time of it and maybe some fun too.
    There are always great little tutorials all over the www.
    The one place that I could find the 555 with a transistor in the timing control is
    look down at circuit 10, Better Timing.
    Oh! Have you tried blocking oscillators?
    How about a Bedini motor or the SSG?
    Very similar circuitry.
    I like to use the 555 though because I knew about it before all this other new hype.
    P.S. What do you think of a Hartley oscillator?
    Have you ever built a radio receiver/transmitter?

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