A problem about a schematic of a Power Supply showed in FAQ

[cibonato]

Hello everybody. First of all ... congratulations to all of the people who keeps this forum going. Sometimes it´s difficult to find specific information on electronics and also help to construct this projects. And now, here is my question: I found at DIY Stompbox FAQ an example of 1/2V+ (the original question is: "Power Supply - What is V.R., V.B, VREF, 1/2V+ etc....?") including the schematic and the values of the resistors and capacitor used. At the "left" of the schematic there is two resistors of 10K each one and also two wires connected to these resistors (one at the top and other at the bottom) but there is nothing saying what these wires are. Well, what do I do with these connections? Where they come from (a 9V battery I guess)?

[Mike Burgundy]

The top connection is 9V (connected to both battery and the circuit where applicable), the other one, coming from between the two resistors, is Vref, or 1/2V.
The two resistors work as a resistive devider. Since both R's are the same value, the effectively cut the supply voltage in half.
This is then used to fool opamps into believing they're running on a +/-4.5V supply.
Have a look at the TubeScreamer schem to see what's going on.

[puretube]

Welcome !

You can see the wire at the top resistor going to a label " +9V ".
Well that is the battery plus-pole.
(Although it also might come from the plus 9V of a power supply...).

On the bottom, the lower resistor and the capacitor are connected by a wire and go to that strange "striped" symbol: that`s the (common) ground.
To this point, the minus-pole of the battery is to be connected.

You can call this point the "zero" (0V)