Did you set the trimpots using the method described in the instructions? From page 12:
"When you are done with your build, you will need to adjust the trimpots before your build will work properly.
You will first want to set the LEVEL trimpot so you can hear the signal before setting the DEPTH SYMMETRY trimpot. This is your overall output control. Without setting it, you won’t be able to set the DEPTH SYMMETRY.
The Internal DEPTH SYMMETRY trimpot adjusts the volume when the external DEPTH knob is full-turn counter clockwise. Use the DEPTH SYMMETRY trimpot to adjust so that you have a smooth volume transition between full turn clockwise and counter clockwise on the external DEPTH knob."
The first part is easy--just set the LEVEL trimpot at its midpoint. This will give you enough output volume to proceed. You can come back to this trimpot after the second part.
The DEPTH SYMMETRY trimpot setting is critical to getting an audible tremolo effect at lower depth settings. Ideally, you want to get the same output from the pedal with the DEPTH knob all the way over to each of its extremes. This is a little difficult to judge because with the DEPTH control full-on, the tremolo effect makes it tricky to determine what the maximum volume really is (unless you're using an oscilloscope). The trimpot setting on my own Harmonic Trem pedal is at about 10:30 (with the midpoint being equal to 12 o'clock), but you may find that you need/want more or less on your pedal.
You can then go back to the LEVEL trimpot and tweak that for unity volume. On mine, that setting is only very slightly past 12:00 in the CW direction. I've noticed that if you dial that up too high, you'll get an audible "beat" signal from the LFO coming through the output.
Using this trimpot adjustment method and with these settings, I get an audible tremolo output down to about 10 o'clock on the DEPTH control.
Hope that's helpful....
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