I'm interested in picking one up but looking for some info. First, the FX loop, series or parallel? The Maz Senior has no controls which leads me to think series. The Studio Lead has send and return level controls which leads me to think parallel. Anybody know? Next, the presence vs. cut controls. Senior has cut, Studio has presence. Difference? Finally, does anyone know what year the "F" serial numbers were made? Any other opinions regarding the Senior vs. Studio Lead are welcome. Thanks.