Power Supply for 9V DC effects running from 9 or 12 Volt AC?

[cjtonic]

Hi all,

since i started reading this forum the number of effects in my rack that need 9V DC increased significantly 

I now need a power supply to get rid of the wall warts. Don't want to have them in the rack but don't want to buy a PedalPower neither because i already a have PedalPower AC and it has one outlet still unused. This means that i can easily get 9 or 12 V AC to power any power supply for 9V DC effects.

Is there an easy way to build such a power supply (providing 9V DC and running from either 9V or 12V AC)? If yes, anything to watch out for?

Thanks for you help.
Cheers
C.J.

[RaceDriver205]

Heres how you'd do it:

Fairly easy to make, with a piece of perf board, and the shown parts.

[cjtonic]

Hi racedriver,

that was quick. Thanks a lot for your help. I just checked some shops for an LM7809. When looking at the pictures there it looked quite massive. Will it get hot? I mean does it have to do any "hard work"? I mean, will i have to provide a heat sink?

What about the diodes, any recommendation which ones to use?

Cheers,
C.J.

[Mark Hammer]

There are generally two categories or strata of 3-pin voltage regulators.  The ones that are the same size and shape as a small signal transistor are content to regulate up to 100ma of current.  The ones that look like power transistors and have a metal tab with a hole (for attaching to heatsinks) are comfortable regulating up to 1 ampere without the need for heatsinking.  If you use the second type, you should have plenty of current for most situations, given that the average analog pedal will need to have <20ma supplied to it, and the average digital pedal will need somewhere between 60ma-300ma.

Note that regulators CAN be "cascaded".  So, for instance, you could have a single 1-amp 15v regulator, whose regulated 15v output feeds a couple of 100ma 12v an 9v regulators, each of whom feed separate outputs.  So-called "double regulation" not only provide several different output voltages, but also provides smoother better-filtered supply current at the lower "second stage" outputs.

I heartily encourage you to consider building a power distribution box.  Imagine a simple plastic box from Radio Shack or wherever, with one input jack, an indicator LED, and multiple output jacks.  Your "master" AC wallwart that supplies the primary regulator goes to the
input jack.  Separate patch cables run from the individual power jack outputs to the various effects on your pedalboard.

There are several advantages to such a system:

• The wallwart can be unplugged and stored separately so that the pedalboard is a "clean pack" without wires and stuff hanging off of it.
• The cable connecting the wallwart and distribution box can be whatever length you want without having top change anything about the pedalboard itself.
• The indicator LED lets you know that the power is still on.
• You can have multiple supply voltages to accommodate the different power needs of various pedals.
• You can have multiple male plugs at the end of the various power patch cables to accommodate different plug/jack types.
• You can disaggregate your power patch conenctions so that you don't have to run a single daisy-chain cable all over the place just on account of that stupid wah
• You can isolate the individual power supply outputs so that line noise from digital pedals doesn't work its way back to other pedals.

I'm sure there are more advantages, but this short list ought to be persuasive enough.

[RaceDriver205]

The LM7805 is fairly small, and it shouldn't have to supply to much power. Effects are fairly low-power devices. Hence a heat-sink will be unnessesary.

[cjtonic]

Thank you guys for your help. Yes, i wanted to create a power distribution box that will be powered by one of the outlets of the PedalPower AC and should itself have around four outlets for my DC effects. Thanks to you i will be able to do so 
I wil post pictures when i am done.

[cjtonic]

Hey guys,

two more questions on this:

1. since i will power this one from AC, how do i ground that thing? I mean where do the connections to ground go?
2. What about the capacitors. i was going to buy electrolytic ones rated up to 25V. Is that ok?

Thanks.
C.J.

[RaceDriver205]

1. The AC plugpack is conncted as per the schem. Each of the down arrows indicate ground.
2. 25V caps is fine

[cjtonic]

Hi Racedriver,

thanks again for your help. I guess i am starting to understand that thing ;-)