Converting automotive 12 volts to 3 volts/dual 1.5 volts

[Peder]

Here's the deal. I have two auxiliary inputs on my car radio. The signal is very weak, so I bought two cheap headphone amplifiers (Fiio E3) to boost the input signal (XM radio and cell phone/mp3 player). The headphone amps work great, and makes the input sound great and full; already tested with no issues.

Problem is, the amps are powered by a AAA battery, so 1.5 volts each. They only turn on when the output of the amp is connected, and last about 20 hours on a charge when constantly on. So instead of replacing the battery every day (I plan to have these buried inside the dash of the car anyway, so the output will always be connected), I want to make some kind of voltage divider/regulator to power both headphone amps when the car ignition is on. So in theory I would have to drop 14.5-ish (engine running volts) to two 1.5 volt outputs to drive each headphone amp.

Any ideas on how to accomplish this?

 

[Arcygenical]

Get a buck converter module... About 5$ on ebay. Something like this.
http://www.ebay.com/itm/LM2596-DC-C...-/151042764421?pt=PCA_UPS&hash=item232ad9ae85

They have pot adjustable models. Just adjust it to it's lowest input and check with a multimeter what the output voltage is upon operation (it may sag a bit, but shouldn't).

Though IMHO, you will be introducing a lot of noise into the audio stream using 12v car power. Remember, the amp is basically floating right now while using a battery power source... You lose this upon hooking up to car power.

 

[Peder]

Well, that certainly makes it easy. And here I was ready to pull out the soldering equipment haha. Thanks!

Yes, I expected some noise to be introduced. I'll try a few different grounding points to help eliminate this. There is always some way to figure that out.

 

[Mohonri]

Along with finding a good, solid ground, it's worth taking a few minutes to add some input filtering on your power--an appropriately-sized inductor and capacitor will do wonders for limiting how much noise can get from your car's electrical system into your buck converter. The buck converter *should* do a decent job of filtering the power, but I'd personally add that extra input protection, especially since the load won't be demanding any large amount of current.