• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tetra Phono Builders...got problems!

Just a warning to Tetra builders. I have seen two people now make the same mistake. If your pre sounds like way to much detail or sibilance it's probably because you left the optional HF shelving resistor R9 out of the PCB. If you don't use the resistor then you have to put a jumper across R9 to make the connection for the HF caps to ground. I found out after some troubleshooting.
The manual for this pre is very confusing

RG