DC9V Power Supply Filtering (Post Wall-Wart)

[thehallofshields]

Hey guys. I was hoping someone could direct me to some information on filtering wall-wart supplies.
Searching has turned up a lot of mentions of a cap and diode scheme to filter DC power, but I'm not sure if these are mean to be implemented inside of an adapter, or if they can be used in a later stage. A general guide or simple schematic would really help.

My Project:
I'm currently building a pedal-board and I've got some extra space in my enclosure that will split my 9vDC, 500ma wall-wart input into two output jacks for daisy chains. I would like to add a power supply filter (just for the hell of it) and maybe a reverse polarity protection diode and a ground-lift option.

[bluesman1218]

Just use the filtering section from the Spyder (scroll down the page for it) http://www.geofex.com/Article_Folders/Spyder/spyder.htm
Make sure your Bridge Rectifier is properly rated for your input voltage.

Most of the wall warts out there are not regulated. They put out more than 9VDC, usually 10 -14VDC. Use one with 500 - 1000mA and there's plenty of current to feed several pedals.

You can build it into a small enclosure with as many jacks as are practical based on your mA output. Just connect your wall wart to the input jack, run it through the filter and daisy chain your output jacks. If the wall wart has + on the tip, just mark your jacks and wire it properly inside.

Hope this helps.

[tasos]

i am so for this too!my brother is looking for some more filtering after his 1spot power supply...[there is no way he will let me touch it ]
any ideas?

[thehallofshields]

Just use the filtering section from the Spyder (scroll down the page for it)

Hey bluesman: thanks a lot for the quick response. Do you know what the "DB01" on the Spyder Schematic is? Are those supposed to be electrolytic cap symbols? If not, can they be electrolytic? I think I'm going to put a reversed diode in parallel with the 220uf cap for reverse-polarity protection.

If I've got a high-quality wall-wart plugged in, could this make the noise levels any worse? - I'm considering putting this filter on a switch.

[ralley]

DB01 is a bridge rectifier used to rectify the AC to DC.  You don't need it if you are just filtering DC.  In fact you wouldn't even need the regulator if the power supply  you are trying to filter is already  well regulated.  The caps shown are electrolytics, doubt you will find any other types for those values.

Rob.

[vendettav]

so, Rob, just 220uF and 10uF caps to the ground? (im talking in-pedal filtering you know) ho about the ol' 100uF to ground trick?

[bluesman1218]

here's the DB101 link on Mouser (yes, the schem says DB01) http://www.mouser.com/ProductDetail/Rectron/DB101/?qs=sGAEpiMZZMvAvBNgSS9LqskCUPWF8KKz

You can access the datasheet from the "Documents" tab

[thehallofshields]

just 220uF and 10uF caps to the ground?

I think I'm gonna try putting the two caps in parallel -> ground. I'll put it on a switch and let you guys know how it turns out.

Also, to go a bit off-topic : what do you guys think about including a ground-lift option?  Will it interfere with a wall-wart? It seems like the power supply filter would still work if I lifted either the input power jack or the output(s) power jack's ground.

[bluesman1218]

If you use the 1st circuit in the Spyder diagram, you can use any wall wart, up to **50V (DB101 data sheet) AC or DC (tip + or -) and it will regulate the output voltage based on the regulator used. I just tested the circuit yesterday with multiple wall warts up to 30VAC and it put out a clean 9VDC.

This is a cool little safety circuit to put between any wall wart and pedal/pedal board, especially if you grab a spare wall wart don't know the polarity and/or voltage.

I tested about 30 wall warts (20 different models), of varying voltages and only 2 models were regulated. I am going to build a few into small plastic boxes and have a few different size input jacks on them so I don't have to cut and solder new plugs on the wall warts. Why do more work than necessary?