The Out Eurorack Module is a 4HP, easy to build output interface able to meet any of your output needs. It includes Left and Right 3.5mm input jacks, a 3.5mm Headphone output jack, as well as Left and Right 1/4" mono output jacks for patching to a mixer, audio interface, effects, etc. The kit contains all the components you'll need to build the Out.
One stereo volume knob controls both the headphone volume and the line out volume. Mono / Stereo inputs let you patch one or two inputs and still make use of the stereo outputs. The line outputs are also normalled and mixed, so patching into only one output will provide a mix of left and right.
The line out is an attenuated and buffered output providing 10KOhm output impedance and a maximum of 9V peak-peak/ 3.2V RMS. This allows a full range of control from consumer line level to guitar pedal-compatible signal strength. Plugging in headphones does not disconnect the line outputs - this allows monitoring a signal that is also being sent out to a sound system.
The headphone output uses dual NJM4556 opamps in parallel - a well-praised technique in Hifi headphone circles. The output stage makes use of the full +/-12V eurorack power to competently drive high-impedance headphones, and the dual opamp outputs provide enough current to nicely drive low impedance headphones.
Design
Out is designed to be a simple output module that can remain patched to an outboard mixer at all times, freeing you to think inside the rack only. The humble Master Volume is a feature I'm always reaching for when performing live or in the studio. Personally, I keep this module as the right-most module in every case, with 1/4" cables running to my outboard mixer and rack effects.
Build
This DIY kit contains roughly 40 components that need to be soldered. In terms of difficulty - more complex than the Atari Goth Console or Simple Gates - but less complex than Quadtec-101. You will need the usual soldering iron, solder, sidecutters - but you will also need wire strippers to prepare the cables between the main board and the jack board. I'd recommend setting aside 2 hours to complete this kit.
Technical Specs
Width: 4HP
Depth: 30mm
Current draw (idle): 20mA @ +12V, 20mA @ -12V
Current draw (32 Ohm headphones driven): 30mA @+12V, 30mA @ -12V
5V needed: No