My understanding is that it has 2 main functions. #1 is to control volume. #2 is allow selection of various source components.
A very good question, @gdaddy1 which you almost answer completely, but I’d say a little off.
Besides source selection, a preamp’s jobs are:
- Level MATCHING
- Impedance MATCHING
- Equalizing (for phonographs)
@gdaddy1 @erik_squires IME preamps have 4 essential functions (this is limited to a line stage):
1) input selection
2) volume control
3) provide any needed gain (as will be the case if a tuner, phono section or consumer tape machine is used)
4) (and this is the least understood) reduce or eliminate artifacts from the interconnect cable between the amp and preamp
Passive controls and TVCs are inherently incapable of point 4) above.
Gdaddy, I hope you understand that running directly out of your DAC is in fact using an active line section. Its dedicated to the DAC of course.
So this comment from your original post is not correct:
Having experimented with 'passive' preamps in the past (McCormack TLC-1) I thought the sound would possibly lose dynamics and bass response would suffer. WRONG!
because you are not working with a passive control right now. Make no mistake- for a DAC to drive a power amp directly the signal must be amplified to meet Redbook standards and that is done with an analog circuit similar to what you find in a preamp line section. As you can see, active circuits work quite well!