The McIntosh is the power amplifier that drives the speakers. The 4-channel device on top left is a 4 channel line-level mixer, a primitive/basic version of a studio mixer that allows basic volume, mute/on-off, and that's about it. Notice the 4 XLR cables plugged into it, they're marked with bands of tape to signify channels 1 through 4. As said in the thread several years ago, this is the "home studio" as of the PS era, and was featured in a European magazine article showing Brian's house. Check the old threads for a photo of Tony Asher there too. This setup was the 1966 equivalent of the "PortaStudio" type of home 4-track that have come back into vogue in recent years among the DIY/lo-fi crowd.
If Brian wanted to record multi-track demos at home, he could do it with this rig. If he wanted to take home 4-track tapes he had worked on in the studio, he could play them back on this rig and also do basic volume leveling and balancing to experiment with mixing ideas. Not saying this deck may not have had more duties than those, but you wouldn't master a commercial album or single in a home studio like this.
It's that simple! Donny, you changed your original post - The thread did get contentious back then because some who actually knew and know what they're talking about got challenged for no discernible reason. Par for the course.
