Wah Pedal Guitar Effect Circuit

This is a design project for guitar effect called Wah Pedal Effect. Wah Pedal has been desing around since at least the early 60’s. The Vox is one of brand guitar effect which  is give beautiful sound and simple, only a couple of transistors and an inductor. The really pertinent question that had puzzled many people - including especially me - is how do you get a moving resonant frequency out of a fixed inductor and a fixed capacitor? How does that silly two-transistor Wah Pedal circuit get a moving band pass out of a circuit that changes neither the inductor value or the capacitor, but only what amounts to a volume pot? This  is the figure of the circuit;

Signals Logic Tester Circuit Using Display 7 Segment

Here’s a design of  signals logic tester that is using indicate on a common cathode seven-segment display, if entry is at logic level "1" (one H on the display) or logic level "0" (one L on the display). If an undefined level is detected will display an "n". When the input is "0", T1 locks and T2 and T3 drive. A level of output X IC1a and "0" on that of IC1b therefore segments d, e and f will be lit. Here’s the figure of the circuit;

When entry is logical "1" is saturated T1 and T2 and T3 are blocked. IC1a's output becomes "0" and that of IC1b becomes "1". Besides segments e and f, already lit will light b, c and g, which results in displaying an "H". When entry is in an undefined state, or is not connected, all transistors are conduction (due to R1, R2 and R3) and the icon displayed is a "n" (undefined). Switching thresholds of the tester are 1 V and 3 V (3 V threshold may be reduced slightly by increasing the resistance R4). Input impedance tester is 5 k, so it does not affect the circuit being tested.