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Metasonix Thryratron Synth; Op Amp Pin out?

Discussion in 'General Electronics Discussion' started by Proschuno, Jun 1, 2013.

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  1. Proschuno

    Proschuno

    87
    1
    Aug 1, 2011
    So I have all the necessary materials to breadboard this, but what is stumping me is the connections it has going into the opamp; pinouts nor a real diagram is given for here, so I'm wanting to know if anyone with a magical crystal ball can decode this... jk, I know this sounds awkward, but I wonder how this achieves a volts/octave response?

    http://www.cgs.synth.net/tube/pic/ts23schematic.gif
     
  2. davenn

    davenn Moderator

    13,669
    1,891
    Sep 5, 2009
    the op amp is labelled as you woud see it

    pin 1 is labelled the rest follow in order anticlockwise around just as it would if you have the chip in your hand :)

    Dave
     
  3. Proschuno

    Proschuno

    87
    1
    Aug 1, 2011
    I see... I'll have to email them, but it seems like a 741 from looking at the connections; the IC is never labeled either, I should have mentioned that.
     
  4. DuctDuck

    DuctDuck

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    Jan 26, 2013
    I know a little about what their circuit is trying to accomplish. You should too if you're trying to build it:D

    I'm sure you understand the CV requirements involved. Any successful design merely processes the CV voltage range to a circuit's (linear) ratio. As you have correctly surmised, the inverting op amp is using a 741 pin out (there are lots of op amp ics using its foot print), it will have a maximum output peak of +/-(6.7V) to feed the VCOs...not the same as the input CV at your plugs but its all (linearly) proportional.

    Like DavenN says, the op amp circuit is straight forward because of pin 1 being identified:)

    p.s.-my voltage figures are only approximations because of things like diodes, capacitance filtering at power supply, etc
     
    Last edited: Jun 2, 2013
  5. Proschuno

    Proschuno

    87
    1
    Aug 1, 2011
    I see, i also posted this to another forum and was told tubes are far more linear than transistors, so there is no need for exponentiation I guess... And upon emailing metasonix said it was a 741
     
  6. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    A musical scale is not linear. Each semitone is about 6% different from the next one (2^(1/12)). This means that a linear change in voltage needs to be changed to a linear change of current and then changed to the logarithm by putting it through a semiconductor junction.

    Transistors or op-amps would do the job equally to tubes.
     
  7. Proschuno

    Proschuno

    87
    1
    Aug 1, 2011
    I see... so the op amp acts as an exponentiator?
     
  8. DuctDuck

    DuctDuck

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    0
    Jan 26, 2013
    Nope...just a regular inverting amplifier...oh, its a non-inverting op amp:eek:! Inverting input's signal is the feedback loop, and non-inverting input's signal is from the CV plugs! Non-linear devices are an element in a negative feedback loop for a non-linear response. Not neccessary for this device.

    From what I remember with CV; a little CV provides an octave change. Not a single note change. I don't know why you would want a smaller frequency shift.
     
  9. Proschuno

    Proschuno

    87
    1
    Aug 1, 2011
    I see, I always thought this: http://www.uni-bonn.de/~uzs159/ the expo converter was required to achieve a volt/octave response, I even see the same guy use one for his thyratron synth.... Wonder why so, if exponentiation isn't needed for tubes.
     
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