12v to 9v = hum?

Frequently asked questions regarding powering your pedal.

12v to 9v = hum?

Postby jimosity » 22 Feb 2011, 08:49

I have a pedal that is running on 12vdc and it works just fine, but I need to power another circuit along with it and tap power off of the one that's working fine. The problem that I'm running into is that there is a hum on the secondary circuit that is power related.
I tried a 78L05 (that's all I had on hand) and the secondary unit powers up and works without hum, but 5 volts isn't enough.
If I get a 78L09 or a LM7809, that tells me that it'll all be good - right?
Is there anything else I can use to reduce the hum aside from a second power supply?

As a matter of fact, the secondary circuit will run fine on 12vdc, but the hum from the first circuit is not an option.
Any ideas?
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