Need some reassurance on an idea for power supply

[spiderman2812]

Hi, I'm fairly new at this as you can probably tell and i really appreciate all the help everyone here has given me. I'm building a regulated power supply in a nice size enclosure 9v dc and i was thinking since there is enough room i also have some pedals that are 24v dc would i be correct in assuming by changing the voltage rating of the caps in the ggg layout and the regulator to an ic78l12 that this same layout would give me 24v dc? Sorry if it's a dumb question! I would also like to know if anyone has a good layout for a 9 volt ac power supply? Thanks Again!! Kevin

[Paul Perry (Frostwave)]

The circuit for a 9v AC supply - if you mean a supply to power boxes that state they need a 9V AC power input - is simply a 9V AC transformer, either in a box of your own, or (and this is what I recommend personally) just a 9V AC plugpack. From www.jameco.com if you are in USA.
And teh thing is this - with DC powered FX, all you have to worry about is, "Is this positive or negative ground?".
But there are a LOT of different ways an AC powered FX might be wired.... and if you try to share a power supply, you wil probably destroy somethng. So unless you REALLY KNOW what is going on inside your AC powered FX, it's definitely one transformer (or wart) per FX. Or you can get a power transformer with completely separate 9V windings for each FX.

[spiderman2812]

Ok so am i s till right in assuming that the regulated power supply will produce 24v dc if i make the changes i discussed above? Here's the link to the layout http://www.generalguitargadgets.com/pdf/ggg_reg_power_supply.pdf

[Paul Perry (Frostwave)]

I don't know where this reference to "24V" comes from..
if you increase the input voltage, increase the cap voltages, and use a 12v reg, then you will get 12v.

[gez]

Ok so am i s till right in assuming that the regulated power supply will produce 24v dc if i make the changes i discussed above? Here's the link to the layout http://www.generalguitargadgets.com/pdf/ggg_reg_power_supply.pdf

To get a 24V DC output, a 24V regulator is required.  Something like the L7824.  A secondary putting out 12V AC isn't enough (as wired) to meet the regulator's threshold though.  Peak DC voltage will be just under 17V, then there's the diode drops of the rectifier to consider.  If the secondary was kicking out more than 12V you could do it.  Alternatively, if the current requirements aren't that great, you could wire up a simple 'voltage doubler' at the output of the 12V secondary.  That would give you more than enough to meet the threshold of a 24V reg, and would be within its MAX input voltage (40V for most).

I can forsee a few problems trying to combine/parallel that with what is shown though...

[spiderman2812]

Thanks for the info i'll just stick with the 9v dc

[Paul Perry (Frostwave)]

  Alternatively, if the current requirements aren't that great, you could wire up a simple 'voltage doubler' at the output of the 12V secondary.  That would give you more than enough to meet the threshold of a 24V reg, and would be within its MAX input voltage (40V for most).

yeah, with so many power supply boxes like Voodoo Labs around giving a couple of 9V AC outs, I'm suprised we don't see more use of simple diode/cap voltage multiplier circuits for eg phantom power & boosters.
http://en.wikipedia.org/wiki/Voltage_multiplier

[gez]

Paul, I mentioned it because I've been doing it myself recently.  Plenty of 9V AC adaptors can be had for peanuts (or found for free).  Not a good idea to run tons of pedals (or one with very high current draw) from a doubler arrangement as ripple starts to kick in (only HWrectified), but a handy little trick.