I like the Sadowksy Pre. I have been using one since the 1990's , a fantastic piece of kit. 
 
	- passive bass it can add heft
 
	- with my MTD it's a smooth and "body" thing
 
	 
 
	As per Luke FRC comment, it is a tone thing
 
	 
 
	Recently I have also purchased a SGFX Beta V . This is excellent for Passive Bass to SS Amp for adding grit and depth not fuzz and brittle. It is a cool pedal.