I have an old Ampex tube tape recorder that I am using as a mic pre. It sounds nice, but I would like to remove all the non-mic pre related electronics to simplify it and also because the caps are the old multi can ones and I need the room inside to put the new ones in. I have unplugged the tape recorder and only want to use the mic preamp section.

My question (and I will reference the schematic below) would be I am thinking I need to disconnect one, three and four from the red block below to remove the bias control and the erase controls. It looks like I need to leave 1 connected, as it is a ground (is this right?)

Then I can disconnect the tape playback by leaving the switch on input (which is what I am doing). I can unsolder the tape side and then remove that section at C2.

Am I way off or am I at least on the right track? Any help would be amazing.