The headphone amplifier Objective2 (O2)
Since we are already advertising unaffordable cameras and other proprietary devices, a reference to an affordable headphone amplifier should not be missing. And we all know that 50 percent of feature films are sound, with Dunkirk it's 82 percent, I've heard. However, in order to be able to deliver good sound, you have to have the necessary equipment to work with sound. The many audio plugins in Cinelerra can only be used sensibly if the devices for monitoring allow a playback that is as neutral as possible.
The Objective2 (O2) from NwAvGuy has been released as Open Source/Hardware (CC-BY-ND) to the general public and enjoys a very good reputation in the DIY community as well as among (audiophile) HiFi enthusiasts. It works both battery powered and with mains voltage, the built-in batteries are even charged during operation by the built-in circuit. The amplifier doesn't rustle or distort, amplifies the signal neutrally and powerfully. For a comprehensive technical description including measurements and comparisons, please refer to NwAvGuy's blog. The headphone amplifier is available in three versions, the mobile analog version, the desktop version with DAC via USB and a stationary combination of analog and digital. It can either be soldered together by yourself or be purchased completely assembled by a professional for a comparatively small extra charge. My analog O2, for example, cost 115 Euro including shipping, it came with charged batteries and now plays with the DT-990 (250 Ohm) from Bayer.