YaranAyr
New Member
I have questions about Op Amps. Please refer to the attached image.
Figure 1 - Inverting Op Amp.
I see dozens of mixer/audio amp schematics that show a wide range of resistor values for Rvol, Ri, and Rf – from Rvol & Ri =1K to 100K
And Rf= 10K to 1M.
I understand that the gain ratio is Rf/Ri.
I DON’T UNDERSTAND the reason for the wide range of values from schematic to schematic..
1. What is Ri for? Impedance?
2. What is Rvol? Just Volume? Or does it create an output impedance for the previous Op Amp stage (if it’s output wasn’t capacitively coupled?)
3. What is the value relationship between Rvol and Ri?
Figure 2. – Single Volt Supply Inverting Op Amp.
I understand that Rdiv1 and Rdiv2 should be equal values to split the Vcc in half.
4. What is the difference between having smaller values as opposed to having larger values for Rdiv1 & Rdiv2?
5. Is there any interrelationship between these two dividers and the rest of the Resistors in the circuit that would dictate their values?
6. If it didn’t matter, would it be beneficial to use larger values just for the sake of having less battery drain through them?
I would like to make a "Universal" Audio Mixer with mic/guitar inputs to line outputs supplied with a single 9.6V supply.
7. Would R values change if I hooked up a single 12V supply?
8. Is there any advantage of having a –4.8V - Ground - +4.8V supply (other than not having to have Voltage dividers?)
9. Any suggestions for a value for Ri for guitars and microphones?
Answers to these questions and any other info/suggestions are appreciated greatly.
Figure 1 - Inverting Op Amp.
I see dozens of mixer/audio amp schematics that show a wide range of resistor values for Rvol, Ri, and Rf – from Rvol & Ri =1K to 100K
And Rf= 10K to 1M.
I understand that the gain ratio is Rf/Ri.
I DON’T UNDERSTAND the reason for the wide range of values from schematic to schematic..
1. What is Ri for? Impedance?
2. What is Rvol? Just Volume? Or does it create an output impedance for the previous Op Amp stage (if it’s output wasn’t capacitively coupled?)
3. What is the value relationship between Rvol and Ri?
Figure 2. – Single Volt Supply Inverting Op Amp.
I understand that Rdiv1 and Rdiv2 should be equal values to split the Vcc in half.
4. What is the difference between having smaller values as opposed to having larger values for Rdiv1 & Rdiv2?
5. Is there any interrelationship between these two dividers and the rest of the Resistors in the circuit that would dictate their values?
6. If it didn’t matter, would it be beneficial to use larger values just for the sake of having less battery drain through them?
I would like to make a "Universal" Audio Mixer with mic/guitar inputs to line outputs supplied with a single 9.6V supply.
7. Would R values change if I hooked up a single 12V supply?
8. Is there any advantage of having a –4.8V - Ground - +4.8V supply (other than not having to have Voltage dividers?)
9. Any suggestions for a value for Ri for guitars and microphones?
Answers to these questions and any other info/suggestions are appreciated greatly.
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