Sawtooth Tremolo

[ppaappoo]

hi, i design this circuit but i don't sure if it's ok. what do you think?

[Taylor]

What kind of feedback are you looking for?

Are you sure that your "speed" control won't also change the waveform? When I've played around with that idea - diodes in an integrator to get a sawtooth - I recall that that resistor acts more like a wave shaper, from saw to triangle. I don't understand what the "led voltage" knob should do if you have a depth which is the current limiter for the LED.

But I would be happy to simulate it for you if you want to check out what it will do.

Your audio section looks fine to me, basically like the  tremulus lune, tap tempo tremolo, and other similar designs. You may find that a cap from IC1b pin 7 to pin 6 helps with ticking. C2 seems small to me, might limit bass.

edit: both opamps in IC2 are drawn backwards - you need to flip the inverting and non-inverting inputs.

Here: play around with this simulation. Your LED voltage control does increase the amplitude of the waveform, but also changes the speed. And your speed control will change the waveform as I thought. I would fix the "LED voltage" and control depth purely with the depth knob.

Check out Dann Green's tremulus lune design at commonsound.org. It's similar and he's got the wrinkles already ironed out.

[ppaappoo]

hi taylor, yes, I use the simulator to design the lfo but I'm not sure about the issue of supply because I want is run with a simple power supply dual no, I'm lost at that point.

in the control voltage of the LED is only to test the circuit and adjust on the fly.

speed control, yes, is as you say, but it was something that interested me more than full control.

if you have the time would be very helpful to me that make the circuit to test and make changes as necessary.

I seek an effect like this in the minute 3.15

http://www.youtube.com/watch?v=xdrqkZlWtMI

[Taylor]

Check out Dann Green's tremulus lune design at commonsound.org. It's similar and he's got the wrinkles already ironed out.

[ppaappoo]

i like the fine/syn pot betwin the diodes. how i can add this pot and the speed control?

[Taylor]

What about your design do you want to keep? It seems to me like you're basically reinventing Dann's circuit piece by piece. Help us understand why you don't just want to build a tremulus lune.

[ppaappoo]

i want the more simple circuit with less knobs, speed, depth and wave shaper
i'll make a new lfo circuit based on the tremulus lune.

[Taylor]

Ok, what I would do is start with the lune, and get rid of the 2 knobs you don't want, spacing and smooth. Hard-set spacing by removing the knob, and connect r7 and r8 directly, and change r7 to 470k. That will bias the opamp to the center of the supply voltage, so the spacing will be 50/50 duty cycle.

For the smoothing pot: I believe at the heart of this oscillator, it's a relaxation oscillator, but it's kind of obscured by all the added controls. The second opamp is there to derive the current to drive the LED. So I'm guessing that lug 1 of the smooth pot will be the triangular, non-smoothed version of the waveform. Connect this point to U2 pin 3.

[ppaappoo]

ok, i'll try thanks

what are those jumpers? J-FINE and J-SYM

[Taylor]

The idea is that the PCB allows you to have either a fine speed pot or a symmetry waveshaper pot, depending on how you fill the jumpers. You select which one you want by following the directions in the bottom left of the schematic.