Step-down 12v to 9v?

[twebb6778]

So I've got a power supply with two 12v outlets, but most of my pedals run on 9v.

Is it safe to step down from 12v to 9v with a voltage regulator built into the power cable, or am I over simplifying it?

Failing this, I might just have to chain two lower consumption pedals to one 9v outlet.

 

[Chuck D. Bones]

Yes, you can put a 12V regulator in the cable. Two caveats:
1) The regulator will dissipate some heat. Most pedals draw 10mA or less. If you power two of those, then the power dissipated in the regulator is 2 * 10mA * (12V-9V) = 60mW + whatever the reg needs to run, usually another 60mW, so 120mW total. That's low enough that you don't need to do anything to keep the regulator cool. Some pedals draw 30mA or more. Suppose you have two pedals that draw 50mA each. Now the power loss is 300mW + 60mW for the regulator overhead for a total of 360mW. The reg will get warm but is probably ok.
2) Some regulators require at least 3V of headroom (difference between input ant output voltage) according to the datasheet, 78L09 for example. You'll probably be ok because that 3V number is worst-case at full power.

The other consideration is maybe you don't need the regulator at all. Many pedals don't mind running at 12V. Is the 12V power supply regulated? What is the no-load voltage?

 

[twebb6778]

It's regulated, but I haven't checked what the voltage is with my DMM.
I'll give it a shot with the 78L09. Thanks for the reassurance!

 

[twebb6778]

Progress update:

For anybody interested in this, it only cost a few dollars, took about 5 minutes to put together and works flawlessly.