http://www.generalguitargadgets.com/pdf/ggg_dist_plus_sc.pdf
I'm looking to understand this schematic. Currently focussing on the input and power stages.
Here's where I'm at:
INPUT
R1 is a pulldown resistor. It provides a path for the leakage current through C2 when the switch is in the 'bypass' position so that un-bypassing doesn't cause a 'pop' noise.
C3 acts as a low pass filter in combo with the source impedance to filter HF noise.
C2 blocks the DC from the supply. Allows proper DC biasing of the input signal.
R5 is a current limiting resistor to protect the op-amp from ESD
POWER
R2 and R3 form a voltage divider so we have V_s / 2 = 4V5 at the output of the divider (our DC bias)
C1 is our power supply smoothing
... what on earth is R4??!
I've asked this question elsewhere & also searched all over the place for answers. I've had very limited success. Often just 'it's there because we need it' type things... I've been simulating these stages (idealised). The non-inverting input value is very notably attenuated without this resistor.
I've heard some things about an input bias current and impedance matching. But I don't think that's so important here as I'm looking at the ideal case (for now) and it clearly has a significant effect on this case.
Any help greatly appreciated!
I'm looking to understand this schematic. Currently focussing on the input and power stages.
Here's where I'm at:
INPUT
R1 is a pulldown resistor. It provides a path for the leakage current through C2 when the switch is in the 'bypass' position so that un-bypassing doesn't cause a 'pop' noise.
C3 acts as a low pass filter in combo with the source impedance to filter HF noise.
C2 blocks the DC from the supply. Allows proper DC biasing of the input signal.
R5 is a current limiting resistor to protect the op-amp from ESD
POWER
R2 and R3 form a voltage divider so we have V_s / 2 = 4V5 at the output of the divider (our DC bias)
C1 is our power supply smoothing
... what on earth is R4??!
I've asked this question elsewhere & also searched all over the place for answers. I've had very limited success. Often just 'it's there because we need it' type things... I've been simulating these stages (idealised). The non-inverting input value is very notably attenuated without this resistor.
I've heard some things about an input bias current and impedance matching. But I don't think that's so important here as I'm looking at the ideal case (for now) and it clearly has a significant effect on this case.
Any help greatly appreciated!