Preamps... understanding volume...

Most preamps do provide gain to the signal. Passive preamps do not.

ozzy

@ozzy - While the majority of passive preamps are attenuators (with 0 dB at full clockwise position), some passive preamps (namely transformer or autoformer volume controls) do provide gain, but not a significant amount.

@sarsicism - To answer your question in simple terms you are trying to achieve the proper gain structure from your source to amp. Most digital sources put out 2V output which is enough to drive most amps to clipping. So a preamp with low or no gain might just be enough for your system (or a digital source with volume control). How low a sensitivity are we talking about with your speakers? Do you have an analog source like a phono stage as well? With analog sources you almost always need some additional gain in the system and the preamp is the most likely place to add it in. I have run analog sources successfully through passive preamps, but today I use a preamp with 20 dB of gain because my two analog sources require it.

My plan is to go Mac Mini to a DAC/Preamp to a beefy amplifier to speakers with a sensitivity of 86 db at 2.8 Volts.
If I had an all digital DAC/Preamp combo that maxed out at "line level", is that enough to reach reasonably loud levels?
Thanks.

Is my understanding that preamps don't "amplify" a variable line out, but only attenuate?I'm trying to understand how preamp selection is important with low sensitivity speakers, even if you have a powerful amplifier.

Well the "variable line out" is the out on a preamp. The key word to understand, what everyone above is sort of but not quite getting, is "line". Line level is around 2 volts. CD, DAC, tuner, tape decks, VHS, pretty muc everything you care to think of is line level. Even the output from a phono stage is line level. In fact the only things you are ever likely to encounter that are not line level are the output from a phono cartridge or microphone. That is WHY the thing you plug your cartridge into is called a phono stage!

Amplifiers also are designed for line level inputs. Pretty much all of them have enough gain to be able to put out full power connected directly to any line level component. In fact, almost all the time all you really need is attenuation. Like you said. So what do you need a pre-amp for anyway?

Well, to conveniently switch components. But also because the design and component selection in line stage components is pretty poor compared to a decent pre-amp. One of the more common problems is impedance matching. Your line component might work great with one amp that has a very high input impedance. This in effect is not asking the source to do much in the way of current. Another amp with lower input impedance might have your line stage sucking wind. Sucking the dynamics and life out of your music in the process.

So like everything else you just have to try and listen and compare.