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Ground referencing when working with opamps

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diy didi

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Good day.
My question relates to two circuits for overdrive sections for guitars. See attached.
In both instances the second opamp’s + input is directly connected to the output of the first opamp. I was taught that the + input should usually be ground referenced via a resistor.
How do these circuits get away with this and not using any resistor here?
 

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Yes you cando that, a noninverting amplifier built with an op amp takes its input on the + terminal.
Your thinking you wouldnt do that to the same op amp, ie connect the + input back to the output.
At least you wouldnt do that for a non weird linear amplifier, you would do that if you wanted to build an oscillator.
 
Good day.
My question relates to two circuits for overdrive sections for guitars. See attached.
In both instances the second opamp’s + input is directly connected to the output of the first opamp. I was taught that the + input should usually be ground referenced via a resistor.
How do these circuits get away with this and not using any resistor here?

You were taught (or understood?) wrongly, it merely needs a DC reference to 'somewhere' - in this case it's the output of the previous opamp, which is most likely at 'ground' anyway, and is an extremely common connection.
 
I was taught that the + input should usually be ground referenced via a resistor.
That's typical for an inverting configuration, but those op amps are connected as non-inverting amps.
 
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