I've built a G-02 Animal kit I purchased from Musikding. It sort of works, but the gain seems to be way too low, when comparing to clips of the real G2. I've tried both with silicon diodes and with various germanium diodes. The diode type makes a difference (silicon results in more gain), but the original is supposed to get lots of gain with germanium diodes. With germanium diodes, my build can barely get a slight overdrive even with a medium-high pickup (EVH Wolfgang).
I've double checked the component values and can't find any errors. The voltages check out more or less (transistor voltages listed below). I did some tests with my scope and a signal generator to investigate the gain of each stage (I removed the clipping diodes for this test, to be able to see the unclipped gain of each stage). I also did some SPICE simulations of the stages:
Stage 1 (buffer 1) - gain 1 (as expected)
Stage 2 (buffer 2) - gain 1 (as expected)
Stage 3 (boost) - gain 2 (too low, simulated: 4.5)
Stage 4 (clip 1) - gain 5 (too low, simulated: 10)
Stage 5 (clip 2) - gain 15 (too low, simulated: 25)
Stage 6 (recovery) gain 8 - (seems OK, simulated: 7)
Stage 3 seems to be the most suspicious part, but I can't find any component errors. I replaced the Q3 transistor, but there was no significant change.
Transistor voltages:
Q1 E: 4.79 B: 5.29 C: 9.04
Q2 E: 5.33 B: 5.83 C: 8.93
Q3 E: 0.19 B: 0.78 C: 4.65
Q4: E: 0.20 B: 0.77 C: 4.71
Q5: E: 0.04 B: 0.62 C: 3.90
Q6: E: 0.99 B: 1.17 C: 5.34
Any help will be much appreciated!