Simple 9v power source kits?

[gutsofgold]

I would like to build a 9v DC power source with variable voltage output (so I can get EXACTLY 9v). I only need one output. I would use my pedal board power supplies but they all vary around 9.4v to 9.7v (OneSpot, Boss, and Ibanez adapters). I'm looking for something cheap, can be adjusted to get exactly 9v, and with just one or two outputs. Is there a nice kit out there?

[ayayay!]

Why not just whip up Beavis's Devolt?   

[jacobyjd]

Last year, a forumite sold me an unopened GGG 9v regulated power supply for $20.

I put it together w/ 4 parallel outputs and it runs like a charm @ 9.01v. I'd recommend it

[JKowalski]

Why not just whip up Beavis's Devolt?  

The Devolt is not suitable for this application, since it drops voltage by adding a significant series resistance to the power supply. You would not get anything close to a stable 9V with the devolt.

The LM317 is an option, but I really don't know how stable it is based on load... There's also some pretty good regulators such as this one:

http://www.st.com/stonline/books/pdf/docs/9050.pdf

Which will give you a +-1% tolerance (8.81-9.09VDC, if adjusted to that voltage) and 1.5-25V capability, and it's an LDO (low dropout regulator, meaning you don't have to have that much higher voltage input compared to output)

Or the non-LDO NJM317F, which at 9V will give an accuracy of +-0.3% tolerance (8.97-9.03)

If you never want it to go anywhere off 9.00000V exactly you can look into lab-quality supplies... But I don't see why someone would need anything better then a tolerance of ~2% for a power supply.

[gutsofgold]

I need something very close to 9v for a transistor gain/leakage circuit I made. I could use a battery but those are never 9v exact either. It just need to be in the 8.9-9.1 ball park. 9.5 was kind of pushing it.

[cpm]

would a 9v1 zener do it?

[JKowalski]

What I would do is put a high-performance regulator inside your circuit box, and use a 12V wall wart to power it (It can be a terrible one too, as long as it puts out ~12V minimum!. That way you don't have to worry so much about having a special power supply (just a 12V one) and you can be sure that it's always on the spot. Just a tiny add-on board maybe with that NJM317F (adjustable 2-25VDC with a 0.03V tolerance at 9V) that I mentioned earlier and a multi-turn trimpot to set the voltage exactly.