Increase master volume beyond maximum in OS X

Solution 1:

http://froyosoft.com/soundbooster.php. Soundbooster comes as lite free version and paid version in App Store (currently around 7 EUR). Does what it say. You set boost once (system-wide), then your volume control works normally, but louder. It is nice to the processor, uses only 2% on my 2011 MBP You have also EQ there and selective volume, but works simple enough to just enable boost and forget. No noticeable quality loss

Solution 2:

There is no way to increase the maximum volume on a mac OS. Like you said, however, there are tweaks that can manipulate the sound to "distort" it and allow for louder sound. One such tweak exists called Boom that does this very thing. Not sure of any free tweaks.

Solution 3:

A DAC/ Headphone Amp should do the trick so long as you output to something other than the built-in speakers. That includes headphones, earphones, in-ear headphones, speakers, and all the Bluetooth equivalents.

There are highly portable ones that are powered completely by the USB port.

The HRT microStreamer is compatible with Mac, Windows & Linux, but not mobile devices.

The AudioQuest DragonFly Red works with Mac/Windows (unfortunately not Linux) but does work with mobile devices such as iOS and Android phones/tablets with adaptors. Note that the red one outputs higher voltage than the black one according to this comparison sheet. This means more gain, and/or that headphones that require more power for the same Decibel can be used compared to the black one.

There are others out there to explore too at varying price points. These are just a couple of popular examples.

Solution 4:

Audio Hijack by Rogue Amoeba can legitimately overdrive your audio, among other things. It's a digital recorder with a real-time audio effects engine. You don't have to record if you don't want to.

To achieve your goal, Add your sound input(s) (Input Device, or Application) and then add an Overdrive function. Options are: Off (no overdrive/100% volume), 2x, 3x, or 4x. I suggest starting with 2x. Select your Output Device (speakers, earphones, etc), and then start the session. This has been the only thing I've found that actually makes the volume louder using software rather than just distorting the audio. Be warned, I have blown out a pair of earphones using this. I suggest using 3x or 4x with great care turning system audio very low and then bringing it back up to a comfortable level after starting the session and selecting 3x or 4x to avoid blowing out the drivers on your earphone/speakers etc. Below is an animated demonstration to show the essentail blocks you'll need to add to overdrive your audio and start a session. Your input or output device or application names may vary.

Not necessary but I use Audio Hijack in conjunction with Loopback to easily select audio sources I want/don't want as my input audio.

Sound Source can supposedly overdrive audio for applications as well, but I have not noticed an increase in volume when I've tried it, I still use it though as it is a really convenient input/output selector than the Mac OS, and it has the advantage that you can control volume for each application independently.