What does a pre amp do


I have been trying to get an answer to this question, but so far have not been enlightened

In a modern system, the role of a pre amp is really questionable.

Historically, a pre amp would provide quite a number of real functions such as source selection, impedance matching, maintain volume consistency from different sources, volume adjustment, mute, balance, even tone control, high/low filters

Today, most people have a single CD source with XLR interconnection, which standardized impedance and signal level. Some CD and DAC (such as wadia) has digital volume control. In fact wadia does recommend people to connect directly to their amps

At least in thoery, the best preamp is no preamp. Even the preamp manufacturers agree as evident by the extent they go to separating power supply, minimize signal path. Then there is the passive preamp

So here is the question, is preamp a historical appendix that audiophiles are afraid to get rid of due to the fear of missing out on some unknown elements of music. Or is it really a percived need created by good marketing programs to exploit audiophiles

The obvious answer may be to try it out with and without preamp in the same system. The results I have heard so far are controversial, some claims much better transparency and clarity while others claim there is a lack of dynamics and less musical

I do not believe answers from "experts" who happens to be in a sales position. They always give a very affirmative answer and yet refuse to let you do an A/B comparision.

Most modern preamps are an empty box, and do we need to pay high prices for a piece of equipment with no known function
ag007
Contrary to your first stated assumption, there are a great many of us who use a tuner, a record playing system, a tape deck, and a CD playing system that does not have balanced connections or a volume control, as well as other sources. For those of us misguided souls, a preamp is kinda handy for providing gain, volume control, RIAA equalization and source selection and to balance the stereo signal between channels, in case our hearing is better in one ear than the other or a room problem causes the imaging of our speakers to be off-center. So preamps are not merely empty boxes, do serve a function, and are not a perceived need created by marketing programs designed to deceive. If your only source is a CD player with balanced outputs and integral volume controls, and you are happy with the sound from it, then you don't need a preamp, and no one is putting a gun to your head to use one.

By the way, why don't you try out with and without a preamp in your own system and listen for yourself instead of relying on what others have said? If you tell me you can't because your CD player has no volume control, then I'd say you could definitely use a line stage, either active or passive, unless you are willing to put passive attenuators on your amp and adjust them with each disk (and possibly track) you play.
I have two passive preamps and one tube preamp. The passives seem to pass along very balanced music and well defined bass, while my tube unit bloated those lower frequencies. However, I greatly preferred the midrange of the tube preamp which was rounder, more dimensional and absolutely involving in a way the passives couldn't match. And for that reason even with the muddier bass, I listen with the tube preamp in place because I love what it adds.
Apologies for any misunderstanding, surely the traditional preamp functions are still used by some, with mulitple sources or need volume control

The question should have been phrased as, is preamp necessary in a system with single source and built in volume control

Unfortunately my cd player does not have a volume control and I do not have an outboard DAC either, so I cannot try this out myself

There are numerous equipment on the market that may eliminate the need for volume control in preamp, such as Wadia, Musical Fidelity pre CD, outboard DACs with volume

So the question is in such scenario, what is the supposed value of a preamp
You have got to be kidding! Buy the best pre-amp you can afford or you are missing the boat. One of the most important pieces in the chain.
Just about every CD player, even expensive ones with a volume control use a cheap pot or digital attenuator and possibly a set of opamps. It's better to use the fixed output and control the volume with any number of good quality passive preamps or standalone attenuators.