Let me start with the Source/Tape switch wiring. Looking at the switch from the back of the panel, am I correct with this assumption: TOP two lugs - Tape INPUT. MIDDLE two lugs - one lug to the right gain-balance control, and one lug to the left gain-balance control. BOTTOM two lugs - the output wires from the INPUT SELECTOR switch connect to these bottom two lugs, AND the TAPE OUTPUT leads connect to these two lugs as well.
It looks like there are single wires coming from the Input selector switch but in the case of the rest of the connections, it seems to be that they are all a twisted pair with none of the ground wires connected. (Not referring to the ground connections of the three controls to PCB here).
OK. This confuses me. Why do we not connect the grounds from the tape input, tape output, leads from the center switch to gain-balance controls. Is there a technical issue or benefit to doing this? It would be simpler to just go by the diagram and run a single connection to the controls. But there has to be a reason for doing it this way.
I've spent a lot of time trying to figure out when ground wires from twisted pairs get connected, and am trying to use the pictures on the web to accomplish that. But sometimes its hard to tell from the pictures because the wires get hidden.
Also, I noticed that the input connections from the master volume control only need a single ground.
I welcome discussion on this. I'd like to build the best pre-amp I can. I know that it's important to get the little things right and that's what I'm trying to do with this posting.