[Jim Andrus]

Title basically says it all. I'm still pretty new in the head fi world, so I don't really understand the purpose of the amps. Do they just make it louder or crisper or what?

 

[PurpleAngel]

Amplifiers increase the power (voltage) that is sent to the headphones.
The power of the amplifier is need to made the diaphragm in the headphone cup vibrate (to create audio).
A normal line-output (which is not an amp) can usually drive (decently) lower impedance headphones, but a dedicated headphone amplifier is better.
Some headphones really improve with a quality amplifier. 
Some harder to drive headphones (low sensitivity and higher impedance) are not really worth getting unless you can connect them to a quality (and powerful) headphone amplifier.
 
Easier to drive headphones (high sensitivity and low impedance) can still sound good without a dedicated (and high priced) amplifier.
Like headphones that are designed more for use plugged into a smartphone or other lower costing portable audio devices

 

[ProtegeManiac]

Quote:

Originally Posted by Jim Andrus /img/forum/go_quote.gif

Title basically says it all. I'm still pretty new in the head fi world, so I don't really understand the purpose of the amps. Do they just make it louder or crisper or what?

 

Amplifiers by the very definition of the term amplify make a signal stronger, therefore it can drive a transducer - headphone or speaker - louder. A good amplifier will not only make it louder, but will do so with very low distortion and noise. Many amplifiers can go well beyond the level where hearing damage is guaranteed, but the sound begins to suck sooner. For example a lot of amps are rated for their power output, the reality is that in all likelihood they can actually make more power, but by that point it's already well into the threshold of audible distortion. By contrast a better amplifier can for example make a headphone play as loud as a small desktop speaker without audible distortion.

 

That said, at low volumes, all decent amplifiers will sound alike, since none of them are anywhere near audible distortion. At what point and at what rate distortion piles on, which sometimes even varies throughout the range (ie some amps are very clean until they get to a certain point where distortion and noise can pile on faster) will vary. The headphone specs also play a part - sensitivity determines how much power is needed to reach a given SPL, impedance can affect how much power it gets from a particular amplifier (some amps deliver more power at either 32ohms or 300ohms). 

 

That said, you don't need massive power that's enough to drive speakers in a small room, to get fairly loud much less with low distortion and noise, much less an amplifier that's nearly the size of an ATX chassis.