So I finished building the MP573 and did all the tests, I thought it was working fine, then I realized the gain wasn't too high.

Checking the voltage of each pin (I didn't write them down), but they were all exact or within a very small margin of the correct figures.
The transformers resistances all seem correct.

There's some heavy saturation/distortion in the signal way before the LED turns red. I put some sine waves through it and they're about 40dB quieter than they should be. To achieve unity on the input I need about 40dB of gain and at that point the top half of the waveform is squared off.

One other thing is that when I use the rotary encoder at 30, 40, 50 and 60dB of gain there's a fairly big pop sound.

I couldn't seem to follow the input with the multimeter, I could only get one value at the input transformer pin 7 and and TP1 and it was the same with or without any input.

Any idea what could be wrong?