Well, any pre amp isn't passive( in the sense it does control volume) but I guess what you are asking is a pre-amp that just has a good quality volume control. Most pre-amps have inputs that control input from various sources; turntables, CD players , cassette players and etc and the pre-amp effects this due to additional circuitry and etc.
Yes, maybe just a straight line to an amp would be nice but in the real world for most people it isn't viable.
Any really, most CD players have enough output level connected to an amp with a volume controller( or some amps with a volume controller) sound very nice.
In short, a passive pre-amp is just a volume controller.
Happy Listening, the Prisoner