what's 'Active preamp' vs 'Passive preamp'?


I thought all preamps are passive in nature, and I heard the term 'active peamp?

what does it mean? how they are different?
eandylee
Transformers can add voltage (gain) but only at the expense of current and add current (gain) at the expense of voltage. Because they are passive, no net increase in energy is possible.

Kal
Eandylee,
I am now using my APL CD Player direct to my Pass Amp and it is better than when I used a Melos Preamp. Sound is purer.
Plus, as was mentioned, I eliminated one power cord, interconnect, rack space .
It really depends on your amp and speakers.
For my setup, no passive unit can make it sound right due to low sensitivity on both amp and speakers.
Ralph, is "controlling the interconnect" impedance matching or something else?