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
Eandylee, most volume controls that are in DACs are not of the best quality- particularly if they are digital. Digital volume controls essentially subtract bits to lower the volume; the result is audible loss of resolution as you turn the volume down. If you want to do it right, an active preamp (especially one *without* remote) will have a better chance of doing the job right- you would run it and have your DAC turned all the way up for maximum resolution.

One other task of active preamps is to control the interconnect cable. If set up properly, the line section of the preamp will minimize or eliminate the effects of the interconnect cable. Be careful though- many preamps may do their other jobs well but fall flat on their face in this department, introducing coloration due to the cable. BTW, this is a serious weakness in 'passive preamps' which in fact are not preamps at all.
Only a brief comment about passive pre-amps and gain. Although passive, if they use transformers (TVC) they can add gain too. Typically +6 dB. And that is sufficiant in most applications.
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.