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Op-Amp circuit: Check understanding I always short in observe the circuit

#1 User is offline   chahua 

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Posted 28 November 2017 - 04:03 AM

Hi to all, this circuit is my homework maybe, I always short in observe the circuit, but I'm really want to understanding ](*,) .So please check my understanding of the components in the following guitar pedal audio circuit and elaborate/ fill in missing knowledge where necessary.

Left of the op-amp inputs

R1 & C1 presents an input impedance to the output of the previous circuit
C1 sends high frequency in the input signal to ground
C2 blocks DC from entering/ leaving via the input
R2 loads the C1, C2, R2 filter network to ensure a high impedance - thus the input signal reaches the non-inverting input of the op-amp and doesn't disappear down C2-C1 to ground
Above the op-amp

R4 and R5 provide a DC-offset for the single supply circuit.
C4 filters ripple & noise from the 9V source and works in conjunction with D1 to 'quickly' pass the AC element of back EMF to ground
C3 further filters the noise and suppresses ripple, cleaning the bias DC voltage
D1 clamps transient current when the DC voltage source is switched on/off (like a flyback diode). The reverse-bias-voltage of the component would have to exceed 9V to prevent the components p-n junction from breaking down (shorting)
R3 presents a high impedance at the junction of the non-inverting op-amp input to prevent the audio signal from input source being filtered by C3
Below the op-amp

R7 // C6 in conjunction with C5, R6 and the potentiometer set the gain.
C6 rolls off 'high' frequencies, reducing their amplification
C5 Blocks DC from reaching ground, thus preventing op-amp saturation from amplifying the DC
The potentiometer enables variable gain, R6 prevents the gain trying to reach infinity when the potentiometer impedance tends toward zero
Shouldn't C5 and R6 be reversed to prevent the DC building up at the inverting terminal of the op-amp? Does this influence build-up of charge & thus saturation?

Right of the op-amp output

C7 Blocks DC from leaving the circuit via the output
R8 presents a higher impedance than C7 and works in conjunction with the potentiometer to provide an output impedance and set the output 'volume' and control the current of the circuit when unloaded? These three components also create a high-pass filter on the output side
D2, D3 and D4 asymmetrically 'hard-clip' the signal for a rough distortion sound
C8 draws high frequencies to ground to avoid being 'hard-clipped' by the diodes D2, D3 and D4
Thanks in advance

Power stabalisation - issues will occur due to C3, C4 and C5 when powering on the circuit. A number of seconds will elapse before the circuit is ready to use at nominal DC bias and gain.
Thanks all.
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#2 User is offline   FZ Fan 

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Posted 30 November 2017 - 08:21 AM

It has been years since I had to use my brain and think about what all those components do.

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