Hi. I'm a newbie.
Hello Welcome and sorry about your wallet.
I didn't know if these 'headphone amps' exist before I come to this website.
Yes for 99% of the music listening public headphone amps don't really exist, or the need for one doesn't exist.
So, what are they for? it seems like they have some sort of tubes. What makes it better?
Amps do several things. Volume boost / gain and attenuation, depending on the volume levels preferred by the user. An amp can color the sound with its own blend of frequency alteration and harmonic distortions. An amp adds dynamic headroom for voltage and current peak transients. An amp also serves as an impedance matching device between the source and speaker (or in this case a headphone driver). Amps are not always better, depending on the headphone and what its plugged into. Grados plugged straight into a macbook Pro for example is a really good sounding setup, and the addition of a second amplification stage is only sometimes beneficial... IMHO.
I have a few good headphones and never thought I will need an additional amplification device for it since I could get enough volume from Ipod.
You might not benefit from an amp addition... depending on the specific player and headphones used.
lease tell me about its benefits. Does it enhance audio quality?
For me personally yes, Amps do increase musical enjoyment.
I know it's a gear that amplifies the volume but why some of them are very expensive? I've seen ones that sell for over 600 dollars. If they were just for volumes, that price doesn't make any sense to me.
Thats a LOADED question. In a nutshell... it costs $$$ to research, develop, field test, market - advertise and sustain/service a product. That has to be balanced against what the consumers will pay. So different products require different financial investments, and they conversely occupy different consumer price points.
As I mention before, its NOT just about volume boost. Amp circuits do sound different from one another.... thats just how it is. Circuit designers tweek and tune their designs for different sonic characteristics. Owners roll tubes and OP amps to further refine the sound.
Hope this helps to clear things up a bit