Our little pet project for the DIY community, the CnB is a mastering-grade unbalanced stereo crossfader.
It's meant to be built into whatever line-level device you want to give wet/dry capabilities - generally this will be for using parallel compression in your VCA compressor or the like.
Recently, someone built one into his own version of the Cooper Time Cube.
AC Coupled / capacitor input version for standalone operation and DC Coupled direct injection version for device-internal application.
Here are the docs and some measurements - frequency and phase response, should be linear well above 20khz.
Construction
Master File
Schematic
Copper Mirror
BOM
Wiring Guide
Metering
Level: 12.2 dBu
Freq: 1031.25 Hz
S/(N+D): 0.0038%
THD+N: 0.0023%
Level: 18.2 dBu
Freq: 1031.25 Hz
S/(N+D): 0.0039%
THD+N: 0.0028%
Level: 20dBu
Freq: 1031.25 Hz
S/(N+D): 0.0049%
THD+N: 0.0042%
Quiescent current draw ca. 70mA including LED (Class A opamp output operation due to pull up resistors). For the graphs above, note there is some fluttering in the meter under about 250-500Hz. I don't know where that slight phase twist up at 20kHz in bypassed comes from but I surmise it's a side effect of there being no load on the DAC output going straight back into the input for measuring. As far as I remember, it did that even when there was no CnB attached at all, and the input was shorted to the output so...yeah. Looks good.