I see that now. Thanks for the explanation.phibes wrote:To explain more on the layout, the red +15V traces are your VDD. They all need to be jumpered together as per the note says. The BBD's don't connect directly to the VDD. The LED is being used as the pedal indicator (it's always on once the pedals plugged in) and to bias the bbds. So the positive end of the LED goes to +15V, the negative end of the LED will be your VBB. If I remember right, the RED LED will cause a 1.5V-2V voltage drop. So that's where your VDD and VBB will be. Way to get major bang for buck out of parts!
I still do not understand why they chose to connect the Vdd to the LED. I would think they would have connected Vdd directly to 15V and then connect the Vbb to the LED (after the voltage drop)
This way, the SADs are performing at an optimal level.
In the end, I suppose there was a reason but I just do not grasp it. After looking at the MXR flanger, it appears they did the same thing (tying Vdd and Vbb together) BUT, they tied them both to the 15V input.