[Theendgamelv3]

So I bought some KRK KNS 6400 and I tested them at Guitar Center with my phone and I thought they sounded pretty good. Go home and plug them in and the sound isn't very loud. The volume is on max and I can't seem to increase the sound. My old headphones are the RS120 Sennheisers which has its own volume I can control. I don't remember if I always had somewhat low sound or not since owning the RS120s. I am plugging the headphones into onboard sound and I know that is low quality. Basically how should I go about improving my sound from my PC for my headphones. If I have to spend money, it would be around 50 bucks.

 

[MrScratch]

An external amp would improve the sound pressure, pushing it above your natural listening volume with ease.
However, you should improve the SQ while you are at it. If you have a laptop with a crappy soundcard then you'll get a crappy loud sound and nothing more.
Maybe you shoukd look for a DAC/AMP combo... The Fiio E10 (or the upgraded version called Olympus) is a nice USB DAC with an integrated headphone amplifier and it will cost you around 50 bucks on Amazon or $ 53 on Adorama (which appears to be an official reseller).

Hope this helps.

 

[PurpleAngel]

Asus Xonar DG (PCI) sound card, $25.

 

[ROBSCIX]

You need to improve your source, but you have a very limited budget. Buy the best card you can afford within your budget.

 

[joe_cool]

It would be better if you could tell us about your source, like PC or laptop. Then describe the audio hardware. The KRK headphones you described have a sensitivity of 95 db which seems low. Maybe you just need more power.