The goals of the preamp are:
- Sounds great. Of course.
- Discrete FET (Field Effect Transistor) design. Discrete because I don't like the sound of opamps, and FETs because the devices operate in a manner somewhat analogous to vacuum tubes.
- Runs off a 9v battery. In practice a decaying 9V battery, possibly as low as 8.0 volts.
- Very high (3.0 Mohm) input impedance. 1.0 Mohm is the minimal acceptable input impedance for a guitar device.
- Medium (6.0 Kohm) output impedance. There's no need for an especially low output impedance as we're only using the preamp to counter the effects of cable capacitance and loading.
- 3 dB gain. You don't need much gain, and given the guitar signal level and the 9v supply voltage, there isn't room for much gain.
- Low noise.
- Graceful overload. Overload happens; the circuit should clip gracefully and recover gracefully.