why preamp?

Because there's the existence of power amps that don't have volume control as well as powered speakers that have independent volume control which would make it a pain to adjust volume.

Normally a preamp is used as a source selector and to adjust playback volume between different sources. In my case I have a pre-amp that takes a dac and a turntable as inputs and controls the volume to an amp for headphones and an amp for speakers. 

Most all amps have a preamp stage but they are just part of the design and not separate components. 

Are you referring to headphone listening? Putting a preamp between your source and your headphone amp doesn't seem to be a common practice.

Preamps are source selector, impedance matcher and volume control units for power amps. In the old days they also did the RIAA correction for your vinyl playback.

Aha, so you have the pre-amp and power amp followed by the source components, cool...

Quote:

Originally Posted by Deep Funk 

Aha, so you have the pre-amp and power amp followed by the source components, cool...

I think it's the other way, source -> pre -> power.

I personally use a pre cos my active monitors don't have (!) a volume control knob
 

My pre-amp is a source selector, Dac,  Phono stage and headamp at the moment, although when I have a proper power amp it will have an attenuator too. They do have a few uses.

Lets say you get this one, to control volume of your powered monitors and to amplify your headphones: 

http://www.thomann.de/gb/sm_pro_audio_mpatch_2.htm

Then you get the cans you like and a couple good monitors, like: 

http://www.thomann.de/gb/yamaha_hs80m.htm

http://www.thomann.de/gb/adam_a7.htm

or whatever you like.  Add a source (that can be an ipod or a computer) and you have a good system for not a lot of money that can compete with many hi-fi setups.  You wont be able to post it in the high-end audio forum, but it will give you plenty of satisfaction, and I think that's what matters to people who are not rich.

I have always considered using a transparent preamp to drive my headphone amps (even if they already had a volume control) for the sake of a remote control... headphone cables are long for this very reason, so my logic tells me.

The pre-amp section of the Lehmann BCL is extremely transparent (dip switches must be set to max gain).  I currently have it pre-amping all my tube amps as I found my amps volume knobs tend to max at 9 o'clock before the phones are too loud - at times at the level I want to listen, sometimes I can really hear mistracking and imbalance at certain points below 9 o'clock.  Using the pre, I am able to leave the other volumes at 12 o'clock and use the more precise tracking on the BCL.  The BCL also imparts certain characteristics to the tube amps, specifically the treble is more extended which helps in the "air" department and there is also a little midbass boost which serves to give an impression of a tighter bass from the tubes.  The transparency cost is virtually negligible - but I do hear it - but the benefits to the sound shaping is worth it.

I have another question regarding this subject.    let's say i have a headphone amp which can be functioned also as a pre amp.  now..i want to use this amp for it's dac and hook it through the pre-amp output to another headphone amp.  am i double amping in this case?

I think we can all agree that the fewer components in the signal chain is best.

Originally Posted by plonter 

I have another question regarding this subject. let's say i have a headphone amp which can be functioned also as a pre amp. now..i want to use this amp for it's dac and hook it through the pre-amp output to another headphone amp. am i double amping in this case?

Yes. The preamp output is the equivalent of a headphone output.

Certainly – if you want high fidelity. I even renounce a preamp on my speaker system and use a passive attenuator instead for driving my power amp. Note the term «attenuator»: It sais that the signal from a CDP is too loud for a power amp and has to be attenuated. Now combine this with the concept of an active preamp!

.
 

Quote:

Originally Posted by plonter 

I have another question regarding this subject.    let's say i have a headphone amp which can be functioned also as a pre amp.  now..i want to use this amp for it's dac and hook it through the pre-amp output to another headphone amp.  am i double amping in this case?

 

I think we can all agree that the fewer components in the signal chain is best.

Yes, you are double amping.
 

Quote:

Originally Posted by Kees 

Yes, you are double amping.
 

can't i set the pre-amp (the first amp with the dac) to output a "line level" stream to the second amp?    and if it is possible,won't it be the same as using a dac output to the amp?
 

With speakers many people use a preamp to feed a power amp to feed the speaker.  There is nothing evil about chaining two amps.  Just hook them and listen.  If you like it, then it is good.