I would like to show you the diagram of a simple guitar preamp unit. It's based only on eight parts (including TL071 op-amp).
The preamp is very flexible in use. Can be mounted in a guitar body - as an on-board preamp or as a part of a guitar effect pedal. It's got low power consumption - perfect stuff for work with a battery.
The preamp is based on a very popular circuit, but with this diagram you will get the clear „how to” that you can easily use in your work with guitar electronics.
As you can see, there's no any volume control. It's just a single preamp unit, that can be expanded. You can add a volume potentiometer on the output, or even on the input (but it will be passive). You can also put some tone stack after it.
Input impedance is 1M ohm (2/2).
The maximum gain level can be adjusted by increasing the value of the resistor, which in this example has got 2k ohms. With this value, gain is 3x – guitar pickup signal power will be tripled. If you will swap the 2k resistor with a 10k one, gain will be 11x (10k/1k + 1).
The 2k resistor will be good, if you want to use this preamp as a guitar on-board unit. The volume control will be precise – not too drastic, and there still will be a place to use a booster pedal, with good results.
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