[sdiy] More on adding analog ins to digital

[Grant Richter]

I opened up a Yamaha DJXIIB and traced out the front panel controls.

The pots are between 0 to 5 volts. They must run to a multiplexor and  
be converted with an A/D.

I added a series of switched jacks to the +5 volt side of the pot so  
that I could insert an external voltage to replace the 5 volts. This  
seems to work fine and the pot can be used as an attenuator.

This spoof may work for other digital boxes that have faceplate pots,  
but not for encoders.