[AveryG]

Hi Jean Pierre, 

I just completed the build of the MP573 and got the expected values with the short circuit check, general power check (23.7V and 23.6V with Transformer plugged in) and the bias adjust (3V). The bright side is I do see the input LED light up when I speak into my microphone, and it also lights up when I plug in my guitar through the DI input. The problem is, I hear no output. What could be the problem here? Please help, thanks. 

[AveryG]

Also, I made sure the Polarity switch is flipped to the left since leaving it in the middle mutes the output. Still no sound. 

[JPK]

Try to follow the signal as shown here.