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Introduction: A simple circuit but still a very useful guitar effect!
This is a classic treble booster circuit for electric guitar. It creates a screaming lead sound when used in between the guitar and a nice tube amplifier. The circuit itself is designed NOT to produce overtones, harmonics or other distortions of the guitar sound. Rather, this circuit is a simple tone stack that boosts, as the name implies, the top end of the guitar's output. It is especially useful when used with a single coil bridge pick-up.
Description: The signal enters via a 1 nF capacitor and is fed directly to the base of the NPN transistor (this can be practically any small signal general purpose transistor 2n2222a etc)
The base of the transistor is biased at just over a volt.
The circuit shows a 10 K resistor in series with the signal generator. This resistor would not form part of the actual circuit but is there to represent the impedance of the guitar AND because in EC, as pointed out by @hurz, we need to prevent the infinite current sinking ability of the simulated signal generator from affecting the circuit!
There is a 10 uF capacitor from emitter to ground. I call this a bleed cap but others call it a shunt or other names. It's function is to dump AC down to ground so that we can think of the signal as starting from ground from here. effectively this allows the 1K resistor to be bypassed and thus increases the gain! IN reality this returns the gain to about parity or 1 X.
Simulation: The circuit is shown here with a frequency to dB plot, as the main function here is tone related. Here we see a steady slope rising up to and beyond the human hearing range.
NOTE: If this were an effect for professional use, I would put a MOSFET input and output stage on both input and output stages. This would ensure a high Z input and provide a better tone effect by having a buffer stage on the output.
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