The 304 headphone amplifier is a one-in four-output amplifier designed to drive multiple headphones of any impedance. A proprietary high voltage drive technology gives the unit the ability to drive high impedance headphones with the equivalent output voltage of a much larger power amplifier, yet provides more than ample current for low impedance phones.
The four stereo outputs of the 304 automatically adjust output power to match the load impedance. Controls provided are input level, output level for each individual amplifier, and a stereo/mono switch. The later switch allows the amplifier to be used several ways. As a normal stereo amplifier (with four outputs), the left and right inputs are used for stereo signals, which feed the left and right outputs. Switching to mono with a stereo input provides a quick check of the mono compatibility of a stereo mix, or allows the user to monitor in mono. As a mono amplifier, one signal fed to either input will feed both outputs. Also in mono mode, when two different mono signals are fed to the left and right inputs, they will be mixed to feed both the left and right outputs.
The inputs of the 304 are electronically balanced, but will operate normally in an unbalanced configuration when 1/4" TS phono plugs are inserted. The outputs are 1/4" TRS phono connectors and are suitable for driving headphones in the range of 8 ohms to 2000 ohms. Used in broadcast, installed sound, and recording applications, the compact half rack chassis permits 8 channels in one rack space.