Hi! I'm trying to build a very simple (step by step) electric bass preamp based on the TL071 opamp. I choose that opamp since it's cheap and very easy to find, and seems that's a standard for this type of applications.
I'm not copying any design, I'm just learning through the process, so I would want to hear some recommendations up to this point.
Here's my current crude and basic circuit in LTSpice (already mounted on breadboard):
My rationale is:
* 100K resistor pair to bias the single-supply to VCC/2.
* 4k7 resistor pair to form "virtual ground" to VCC/2 ( I also tried 1K / 1K in breadboard to maximize waveform distortion)
* Pot_Gain: a potentiometer to control gain/drive level.
Of course, I expect my first approach (I'm a beginner, remember ) to be very crude.
I want some recommendation on my following thoughts:
- Does the 100K divider form a 50K ohm input impedance? I've seen audio circuits for electric guitar with 1M or 2M impedance at input. For electric bass, it's probably at the same league.
- Does the gain resistor (and the resistor network) affect the input impedance due to the feedback circuit? I tried fairly large values (470K or 1M) and the op-amp clipping seems very distorted (which is what I expected) but signal loss was evident.
Just for completion, here's the output waveform (after the C2 cap) for several pot_gain values from 5K to 100Kohm:
Thank you very much for your patience.
I'm not copying any design, I'm just learning through the process, so I would want to hear some recommendations up to this point.
Here's my current crude and basic circuit in LTSpice (already mounted on breadboard):
My rationale is:
* 100K resistor pair to bias the single-supply to VCC/2.
* 4k7 resistor pair to form "virtual ground" to VCC/2 ( I also tried 1K / 1K in breadboard to maximize waveform distortion)
* Pot_Gain: a potentiometer to control gain/drive level.
Of course, I expect my first approach (I'm a beginner, remember ) to be very crude.
I want some recommendation on my following thoughts:
- Does the 100K divider form a 50K ohm input impedance? I've seen audio circuits for electric guitar with 1M or 2M impedance at input. For electric bass, it's probably at the same league.
- Does the gain resistor (and the resistor network) affect the input impedance due to the feedback circuit? I tried fairly large values (470K or 1M) and the op-amp clipping seems very distorted (which is what I expected) but signal loss was evident.
Just for completion, here's the output waveform (after the C2 cap) for several pot_gain values from 5K to 100Kohm:
Thank you very much for your patience.