x0x:voltagecontrolledoscillator
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x0x:voltagecontrolledoscillator [2007/09/30 18:26] hl-sdk |
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| The first part of this section is IC9, a 74ac174 Flip Flop, which takes 6 note inputs from Port C of the microcontroller and a clock signal (called Note Latch). On every clock signal, it samples the binary value from the note inputs, and outputs it to a 200K resistor network where it is added with the 5.333 Volt supply. This resistor network by virtue of math I do not understand takes the binary output of (for example) (010111, middle C) and mangles that into 3Volts. This of course, becomes the control Voltage. | The first part of this section is IC9, a 74ac174 Flip Flop, which takes 6 note inputs from Port C of the microcontroller and a clock signal (called Note Latch). On every clock signal, it samples the binary value from the note inputs, and outputs it to a 200K resistor network where it is added with the 5.333 Volt supply. This resistor network by virtue of math I do not understand takes the binary output of (for example) (010111, middle C) and mangles that into 3Volts. This of course, becomes the control Voltage. | ||
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| ==== The Slide Circuit And Buffer ==== | ==== The Slide Circuit And Buffer ==== | ||
| + | I'm surprised no one wrote about this before, as it has a lot to do with slide time, and it's fairly simple to analyze. | ||
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| + | {{x0x:slide.png|Slide Circuit}} | ||
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| + | The noninverting op amp somehow works very well together with the DAC network to provide unity gain and buffering. That is... when the 4066 is turned off! | ||
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| + | When SLIDE is HIGH, Q29 and Q30 are both turned on, and this should pull IC12C and IC12D closed (it is an analog switch chip) so that no signal flows through across the capacitor. This seemed a bit unusual to me because that means that slide would normally be high. So when SLIDE goes LOW, the transistors are turned off, allowing IC12C and IC12D to turn on, and allow the tuning voltage to flow across C35, making it lag if it changes. This creates a pitch sliding effect, instead of an instant change. | ||
| ==== Oscillator Drift Compensation and Tuning ==== | ==== Oscillator Drift Compensation and Tuning ==== | ||
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| specified max base current. The same applies to Q25 and Q24 (remember | specified max base current. The same applies to Q25 and Q24 (remember | ||
| tempco compensation, Q25 and Q24 should be the same type) | tempco compensation, Q25 and Q24 should be the same type) | ||
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| ==== Saw to Square Waveshaper ==== | ==== Saw to Square Waveshaper ==== | ||
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| After the saw wave gets passed through the JFET and heads out to the waveform select switch, it heads into a jungle that I can only assume is a waveshaper. Here's a picture of the circuit: | After the saw wave gets passed through the JFET and heads out to the waveform select switch, it heads into a jungle that I can only assume is a waveshaper. Here's a picture of the circuit: | ||
| {{x0x:waveshaper.png|}} | {{x0x:waveshaper.png|}} | ||
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| + | {{template>.templates:fabmenu}} | ||
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