T&L Publications

Is there a way to use 2x -> 9V batteries that gives 18V to produce + and – 9V? How do you hook it up?
Thanks.

Place the batteries in series by connecting the negative of the first battery to the positive of the second battery.
Now you have a 18V battery pack as measured between the free ends of the batteries. If you take your circuit
ground from the connection between the 2 batteries, you create a +9V (first battery) and -9V (second battery)
as measured from the free ends to the "ground" connection. Verify that by using your DMM set to the appropriate
range, placing the black probe on the "ground" connection and placing the red probe on the free ends of the 2
batteries. When you touch the + terminal of the first battery, it will read "9" (or close to it, depending on battery
freshness). When you touch the - terminal of the second battery, it will read"-9" (or close to it as above).

That's basically it.

CeaSaR

So, the actual ground connection is the one between the two batteries, that's the negative side of one battery and positive side of the other battery. And,if I want to bring a signal into this I just use 555 or a crystal, depends on f, that should be a correct conclusion, right?
Thanks very much CeaSar.

This is just your power supply. Bringing a signal in depends on your circuit.
For a clarification on what I tried to describe above, here is a circuit I threw
together for another project. The values are different, but the idea is the same.
Just substitute your 9V batteries for the 16V wallwarts and 18V for the total.

That looks good. I actually could use + - 15V and so using 4 of 9V with some regulation will do the trick.
Thanks much.