Home Forums GuitarPCB Build Support Adjusting BIAS Reply To: Adjusting BIAS

  1.  Looking at the schematic you can see that the lug 1 (identified by a dot) of TR1 connects directly to the Drain of Q5.  To measure the voltage, place your red probe on lug 1 and the black probe on any ground point.
  2. On the Ratt, TR1 is not setting bias of a transistor.  It is changing the frequency response of the IC.  There is no need to measure a voltage here.  The instructions tell you that this is part of the Ruetz Mod.
  3. Since you have a LM308 you should use that for best results.  While other opamps may function in this circuit, they all will have some values that vary from the LM308.  You can look up the data sheets for the others and compare the electrical characteristics, but that may just confuse you further.  Or, you can just plug them in and see if they wlll work.  If the pin pattern is the same, they will probably function.  “Your results may vary”.