Ultra Flanger

Design by John Hollis

Courtesy/Thanks to: John Hollis

Description: Schematics and PCB's can because of copyright issues not be found here. Please visit the Geofex homepage for Schematics, pictures and other files.

The Ultra Flanger is John Hollis' design of a very flexible flanger based on
the MN3007 bucket-brigade analog delay chip.
U1A is an input amplifier and mixer. The input signal comes in through C1
and R2 where it meets the Regen feedback signal from one side of the
Odd/Even Regen switch. R1 is a pulldown resistor to prevent popping when
switched. R3 biases U1A (and through it U3 and U1B) to Vbias1, about 4.9V.
U1A has a slight gain boost.

The output from U1A goes to two places: through R5 to the input to U2 for
delay processing and to the output through R12 to be mixed with the delayed
signal out of U2. The signal level at the input to U2 is limited by D1 and D2 -
these are not for deliberate distortion. The output of U2 is available at pins 7
and 8, and this is then applied to U1B, which low pass filters the delayed
signal to remove the sampling noise caused by U2's analog sampling. The
lowpass filtered signal is mixed with the dry signal through R13, and goes to
the output jack through C5. The output of U1B also feeds the Regen control to
determine the amount of feedback to be mixed with the input.

U5A serves as a Schmitt trigger to determine the min and max size of the
LFO triangle wave. U5B is an integrator that ramps up and down, controlled
by the output signal of U5A. The amount of U5A's output that is applied to
U5B's input is controlled by the Rate control; this determines how fast the
integrator ramps.

U5B's outpu goes to the Sweep control, which determines how large a
triangle wave is fed to the high frequency clock generator, U4. The triangle is
further smoothed by R23/C9.

U4 generates a biphase output on pins 2 and 3/4 at a speed determined by
the voltage on its pin 9. This output is between 50kHz and 1MHz. It is buffered
by the paralleled sections of U3, and this drives the clock inputs of U2.