Passive Preamp - What makes it work?

A passive preamp is essentially a potentiometer (really, 2 for stereo). Used only to attenuate (decrease) the level of the source feeding it.

In order for a passive pre-amp to operate ideally in your set up, you would want to make sure the CD player has a output that is high enough for you to be happy with the listening level in your room. A pre-amp's job is to take an input signal from a source component, and either attenuate it, or add voltage gain (thus making it an active preamp requiring a powersupply) in order to for you to choose a comfortable listening level. One good way to see if your CD player has enough juice, is to hook it up directly to the McIntosh power-amp. Pick a CD that you know has a piece that starts out very quietly so that you dont kill your ears or blow your tweeters (classical music is good for this). If the level is loud enough for you, then you're all set. You should know that this is as loud as it's ever going to get with a passive pre-amp (In an ideal world, with the volume turned all the way up).

Output impedance, in this case, is really not going to be an issue. Your McIntosh's 220k input imedance is high enough that unless the output impedance of your CD player is outrageously high, the passive pre-amp (essentially a potentiometer) should not affect things that much. Impedance matching is definately not wanted in this case. At line levels, you want a maximum amount of Voltage transfer. This occurs best with a very low output impedance feeding a very high input impedance.

What does a passive amp do that's better than one that's not? Does it have benefits? I'm not educated enough to know what a passive amp is used for?

Would not a regular pre-amp always be better than a passive?

Theresa, there are (as always) several views on this subject.

Some say that passive preamps are superior and follow the "less is better" rule. A passive preamp can only cut signal. It cannot increase signal if needed, nor can it actively impedance match between multiple components.

Others believe active preamps are better because they can more effectively manage all types of signals. Active preamp's have many more parts, require power and process the signals fed into it, often adding their own personality (for better or worse).

Some Audiogon members go the no preamp route. Instead they choose a CD player with a volume control and drive direct into the amp.

All three answers are correct provided you have the right combination of equipment.

Theresa,
I just copied the Q&A section from Placette Audio's website in an ad I posted for a passive (placetteaudio.com). It addresses your question and you may find it interesting. I think the Q&A section was listed on the bottom of the list on the left hand side of their home page.

C.