Power supply filtering, some advice please.....

[Xavier]

I'm using a cheap wallwart which is most than probably unfiltered. This means all of my pedals go "hmmmmmmm" . I always put an electrolytic cap across the dc plug poles, and a 100R resistor in series with the 9V+ pole. However this doesn't seem to work. Maybe I need a regulator.

Is there any simple circuit I can attach to my pedals in order to get rid of the hum?

[Zero the hero]

Does the humm appear qven if the stompboxes are battery supplied?

[Gila_Crisis]

on my diy pedals i use this filter:

is taken form the dunlop crybaby

here some pics:

[Joe]

http://www.eidusa.com/Electronics_Voltage_Regulator.htm

A large amount of filtering (10,000uF) might also work, but the regulator is smaller/cheaper.

[Xavier]

Does the humm appear qven if the stompboxes are battery supplied?

No, only with some wallwarts, like the one I have for testing pedals. I mean the 7809 regulator basically provides 9V regardless of what the input voltage is (7-36V). But does it also take care of the hum?

[Sir H C]

Does the humm appear qven if the stompboxes are battery supplied?

No, only with some wallwarts, like the one I have for testing pedals. I mean the 7809 regulator basically provides 9V regardless of what the input voltage is (7-36V). But does it also take care of the hum?

The 7809 requires a couple volts over the 9 volts out on the input supply in order to regulate, otherwise it acts as a resistor in series with the supply.  The specs sheet should say the required headroom.

[Ardric]

I'm using a cheap wallwart which is most than probably unfiltered. This means all of my pedals go "hmmmmmmm".

So that's one wallwart powering a bunch of pedals, all in parallel?

I always put an electrolytic cap across the dc plug poles, and a 100R resistor in series with the 9V+ pole.

Just to confirm, the positive wire goes from the brick, through the resistor in series, then to the cap, right?

I'm wondering if it couldn't also be a ground loop.  All the pedals share a ground through the wallwart cable, and they share a ground through the signal connections too.

[Xavier]

on my diy pedals i use this filter:

is taken form the dunlop crybaby

here some pics:

Thanks to all for your help.

I've just built this little filter in my Dr. Boogey. End of problem. No more hum and 9,2 volt at the DC input. And it sounds better whatever the reason is.

You made my day

[Gila_Crisis]

i'm pleased you solved the problem   

cheers Joel