Powell's „buzz“ parallel bus is an overdriven Neve 1073 preamp for distortion.
The EQ section is engaged but flat, except for the low-cut filter, which is set to 60Hz.
The "buzz" bus runs parallel to two compression paths and adds harmonics and presence to the vocal. It makes it sound more interesting and characterful.
The „buzz“ bus is usually lower in level than the other two paths, but ultimately its level is song-dependent.