I have found that the more runcible a circuit, the more it sounds like a tube amp.
In the Poptronics circuit, the AC gain is not affected by the bias Voltage set pot R5 because that pot is bypassed by capacitor C3. One little quirk of the circuit is that setting R5 doesn't track the main power supply. As the power supply sags, the Voltage at the + side of C5 doesn't move much. This works to your advantage if you use a soft power supply. You get more compression and touch sensitivity.
I have attached my version of a similar circuit. No global AC feedback puts the gain up around 100. The output impedance is not as low as you might think, but it depends on the beta of the output transistors you use. In the one I built, it was around 5 Ohms. Power the preamp from a decoupled supply from the main Voltage rail. Add enough capacitance to stop the low frequency motorboating.
In the Poptronics circuit, the AC gain is not affected by the bias Voltage set pot R5 because that pot is bypassed by capacitor C3. One little quirk of the circuit is that setting R5 doesn't track the main power supply. As the power supply sags, the Voltage at the + side of C5 doesn't move much. This works to your advantage if you use a soft power supply. You get more compression and touch sensitivity.
I have attached my version of a similar circuit. No global AC feedback puts the gain up around 100. The output impedance is not as low as you might think, but it depends on the beta of the output transistors you use. In the one I built, it was around 5 Ohms. Power the preamp from a decoupled supply from the main Voltage rail. Add enough capacitance to stop the low frequency motorboating.