[ryokoseigo]

First question-
I recently tried using my headphones in a different jack on my pc and realized that the front jack is about 30% louder then the back and speaker adapter jack.  Is there any reason for this?  The front jack also has some static which the other two don't have.
 
Question 2:
I'm using JVC rx900's which for the most part I love- best ive tried thus far.  But they are a bit quiet, I need to crank pc sound up to 50% for most things, and sometimes when a quiet audio plays It simply wont go high enough- although this is rare.  would it be a good idea to grab a (cheap) Dac/amp to fix my issue?  Would a dac alone give me the volume of the front jack, or would it need the amp to do that?
 
 
Also when I say cheap I mean the like 20$ cheapo dacs, was looking at
PCM2706 + CS4344 +Dual TDA1308 or the ELE EL do01/2
 
Why cheap?  Because I'm unsure of how much of a real world difference it will make.  Thanks for your help!
 
Also can anyone explain why everyone seems to say that an amp will make a huge sound quality difference?  Isn't an amp just volume?   And if the music im listening to is already super loud wouldn't an amp be pointless?

 

[billybob_jcv]

It's not that simple. This is actually a complex topic, and I'm sure I am going to screw-up trying to explain it. But, here goes...

An amplifier provides voltage and current based on what is demanded by the load (the headphones). The load varies based on the characteristics of the input signal's frequency, amplitude, etc (the music).

When the demands of the headphones cannot be 100% satisfied by the amp, the amp doesn't just output zero - it just does the best it can. Low volume is just the most obvious way you see this issue - but there are others. Music is very dynamic, and there might be very short transient peaks that may jump well above the average overall volume. Consider that powerful initial millisecond of a drum or cymbal strike. If you lose that peak, you still hear the drum strike, but it's probably less impactful & less dynamic. The music might sound more constricted and dull. One of the ways that we might try to overcome this is by increasing the volume. This does raise the peak, but also raises everything else, and although it's louder, it's not really *better*.

There are also other aspects, for example, if your PC or phone has a cheap amp, then increasing the volume might also dramatically increase the noise and distortion the cheap amp is producing. Using a better quality and more powerful amp allows you to run it at a lower volume setting that might have a much lower noise level. There might also be advantages to using an amp with a much lower output impedance - especially with lower impedance headphones (as long as the amp gain is not too high).

Not every headphone needs an amp - but when they do, they do!