The title is an exaggeration, given that the gain of the circuit is intentionally low. When we talk about pre-amp, you can expect amplification often great … that is not the case here. The purpose of this Guitar preamp circuit is mainly to provide impedance matching to allow the use of long cables between a guitar and an amp, while limiting losses to the maximum audio. Although originally this circuit is provided with a gain setting, we will see that it is entirely possible to delete it.
This TL071 integrated circuit can be replaced easilyby an LT1012, a TL061 (which consumes a little less than the TL071), or even by a TL081. With the components shown in this circuit will get 110k ohm input impedance. If this value seems a little low, you can increase the value of the two resistors R1 and R2. Using two resistors 1MOhm, you will get the input impedance of about 500k ohm.