This collection of Grado headphone modifications comes from posts by Skippy, Beagle, TimD, Voyager, Neruda, Chych and Squirt in the HeadWize forums and from Kevin Gilmore's Pure Class A Dynamic Headphone Amplifier project.
http://headwize.com/projects/showfile.php?file=grado_prj.htm
Most of my experience is with electrostatic loudspeakers (Quad ESL63 and my own designs). I have some Koss ESP9/50 phones, but on the two occasions when they have had problems, I took advantage of the lifetime warranty and let Koss fix them.
http://headwize.com/projects/showfile.php?file=rehorst1_prj.htm
This headphone amplifier features selectable gain for compatibility with different headphone impedances (and efficiencies). It has two gain stages.
http://headwize.com/projects/showfile.php?file=simpson_prj.htm
First, the sound of a source to the right side of the listener (e.g., the right loudspeaker in a stereo setup) not only reaches the right ear, but attenuated and delayed, is also heard by the left ear. The level of attenuation and the delay time of this crossfeed signal provide important directional information.
http://headwize.com/projects/showfile.php?file=meier_prj.htm
While doing research for the article Designing an Opamp Headphone Amplifier, I built a portable headphone amplifier for testing purposes. Each channel uses a single Burr-Brown OPA134 opamp in a non-inverting configuration.
http://headwize.com/projects/showfile.php?file=cmoy2_prj.htm
The idea behind the portable DAC is to get better sound than from the line out or headphone out of portable CD player, a pc sound card or other digital audio source.
http://headwize.com/projects/showfile.php?file=ifkovic_prj.htm
The headphone amplifier with the natural crossfeed filter published on HeadWize in fact was my first DIY-project. I built this device because I was unsatisfied with the sound reproduction via the headphone-socket of my CD-player.
http://headwize.com/projects/showfile.php?file=meier3_prj.htm
The idea behind the portable DAC is to get better sound than from the line out or headphone out of portable CD player, a pc sound card or other digital audio source.
http://headwize.com/projects/showfile.php?file=noise_prj.htm
Have there been times when you wished you had more headphone-drive capability from your tape recorder or compact disc player? If you are using digital recording and playback equipment, low-noise operation is especially important to you.
http://headwize.com/projects/showfile.php?file=eaton_prj.htm
The goal of this second version of my headphone amplifier is of course to get a very good sound and still keep it easy to build. Easy to build is an argument for keeping the number of components as low as possible.
http://headwize.com/projects/showfile.php?file=jorgen1_prj.htm