Utilitarian audio and CV mixer

Combine up to four audio sources into one output, with independent manual level control.
It can be used as a four-channel mixer or as two separate two-channel mixers, depending on the connection.

If a cable is connected to the Master output but not to the 1+2 output, all channels will be summed at the Master output. If both the Master and 1+2 outputs are connected, the Master will output the mix of channels 3 and 4, while the 1+2 output will provide the mix of channels 1 and 2.

Each pair of channels has an LED indicator that shows the presence of a signal.