Hey, i think the right resistor is labeled R58 for the avt100. I've done my research and compared the schematics. The R58 its in page 2 of avt100_60_02_iss1.pdfI know this thread is old but I am having a problem with a AVT100 112 Combo and want to mod the FX loop to serial. I have opened it and looked over the board but do not see a R91 or R92 anywhere. Any help would be appreciated, parallel fx loops are worthless and I cant use my fx unit in the 4 channel method... Love this amp but need that to work or it must go!