Greetings humans!
I was in the middle of building the Simple LPF when i realized that I didn’t actually have a power supply that could provide +12v AND -12v. I ordered one of course, but is there a way of bodging something together to test the circuit so i don’t have to wait for power to arrive?
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Sixteen AA batteries?
Probably best to just wait for the ±12V supply.
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I might try that, thanks!
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Well, if you manage to produce ±12 V you’re not really faking it 
but the answer very much depends on what voltage sources *and* components you have access to.
E.g. if you have a regulated 24 V you can construct a 12 V rail and use that as 0 V (with the original 24 V as ±12 V relative to that) but that’s easy only up to 20-50 mA maybe and you’ll end up with multiple ground levels. You can use charge pumps or switch mode converters to invert DC voltages, but those require specialized components and are much harder to build. Or if you have 12-15 V AC you can rectify, smooth and regulate that with some relatively simple circuitry, but then you’ve built a “real” supply 
So a bunch of AA batteries isn’t a bad option, if you have them and cannot wait.
EDIT: Two 9 V batteries might be good enough for many circuits, btw. You may have to dial down the signal levels a bit, since many circuits can misbehave if the opamp inputs/outputs get too close to the supply rails, but the circuit itself should work (and if you use eight rechargeable AA cells per rail, you only get 8×1.2=9.6 V anyway).
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If you have 2 isolated 12V transformers (wall warts) you can plug em up in series and use the connection point as your “ground”. Just check to see if the ground on the output of the wall warts aren’t referenced to the plug ground>. I would also recommend using old style bricks for them instead of the more modern switching transformers as they could introduce some weird instability. Lastly if it’s possible use 2 warts of the same rating, although if they’re both similar enough and capable of handeling the current you require it shouldn’t matter too much.
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In the Power supplies choices? thread, I put this schematic which has been working great for me:
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Thanks for all the help! To be honest I got bored and built a fuzz pedal instead, but I’ll definitely use some of this advice if I suddenly get the urge to finish the filter before the power supply arrives. You guys rock!
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Yeah, I just meant to give a schematic for that idea.