power supply and voltages?

[zeppelinchld]

im confused about what im supposed to do when the schematic says +4.5V or something other than +9V?

[Paul Perry (Frostwave)]

Safest thing, is three 1.5 v batteries in series. (It's easy to find holders for four batteries - then you just connect wire across the empty one).
Or use an adjustable regulator chip, setting the resistor values to give 4.5V.

[demonstar]

I'd use a potential divider to get 4.5v.

Do you need +9V and +4.5v in the same circuit? 4.5V (half supply voltage) is often sent to the  noninverting (+) input of the opamp to bias it. I'm sure theres many other cases for needing +4.5v too but thats the common one I come across. In that scenario you would need both +9v and +4.5v in the same circuit. If that is the case I or someone else can help you with that.

Do you have the schematic?

[JHS]

Zener-diodes are a good soulution to obtain different voltages in a circuit but you have to calculate the "neded" diode value considering the pre-R and the losses.

If the supply voltage is less than 9V a 061 opamp (or similar) connected to +9V can be uses as a voltage-controller.
The same circuit can be used as a Sag-control for fuzzes too, IMHO works way better than the primitive starve-pot solution.

A charge pump connected to +9V can supply +18V.
+12V can be generated from a +9V supply with a diode-cap cascade.

Combinations of those methods are possible too.

JHS

[PerroGrande]

When you see a "mid supply" voltage like that, it is almost always for the purpose of biasing in some way.  This is quite common when running a standard op-amp from a single supply, for example.

There are dozens of ways to do it, but the most common is to simply use a voltage divider circuit using two equal-valued resistors.   For low-current applications and/or applications that can tolerate mild sagging in the bias voltage, this is usually sufficient.   Another method is to us an op-amp or an LM386 to produce the midpoint supply voltage.  Zener diodes, regulators, and the other methods mentioned will also work. 

[petemoore]

Another method is to us an op-amp or an LM386 to produce the midpoint supply voltage.

  Simple, Quick and, Gnd gets Gnd., V+ gets V+, your LM386's output is 1/2v of supply, takes a bit more board space than a resistor divider, won't drive a big *current, costs a bit more, works great for *most effects, providing an accurate/smooth 1/2v.
  Basically all the 4.5v's [which is also often called Vbias or 1/2v]...[on a schematic with an 'assumed' power supply divider], they all connect and get connected to your 4.5v output you made [and measured with DMM].
  Some schemetics just assume power supply, that you'll get a divider of your choice going which outputs 1/2v.