9V and 12V Power Filters

[tranceracer]

I'd like to place a power filter on one of my pedals.
Just curious if anyone has a favorite power filter schematic that they use.  Is the Crybaby filter in the gallery good or any recommendations or links to other recommended filter schematics?.

http://www.aronnelson.com/gallery/v/Xaviers-shrine-of-noise/Layouts/9V_filter.gif.html

Can this filter be used on 12VDC?

Thanks!
-tR

[darron]

most pedals will have a filter similar to that in them already. it doesn't create a regulated supply, it just smooths out the spikes a bit. the 220uf is quite large (you could even increase this to 1000uf or 2200uf!). Check your pedal, see if it has a 100uf or greater cap in it somewhere that connects directly or almost directly to power and ground.



The large polarised capacitor is to hold a large charge which is available to dump if the circuit needs it in moments. It will smooth out spikes in the power. The non-polarized one, with the resistor I think people put in there to theoretically filter out a bit of supply noise that a polarized one isn't trusted to do. You could even use a greencap of 0.33uf maybe. The diode is just there for a bit of protection for if someone connect the wrong polarity power supply to the effect. If your circuit needs protection, then it probably has something like this already too.

You can definitely incorporate this into a 12 volt circuit. Just make sure that the capacitors are rated at around twice (or more) the supply voltage. It's pretty hard to find capacitors that are not rated at that anyway.

[tranceracer]

Hey Darren,
Thanks for the reply!

Along the lines of what you mentioned, I wonder if there is a simple filter ckt to clean up any noise from 9/12V power transformers?

I remember someone posted a simple schematic of a power filter he uses on all his pedals but I cant seem to find it in the search... I'll continue to search for this thread and post if I find it.

Thanks again!
-tR

[darron]

yeah. definitely. build a regulator. for the power you want to output, you need a few volts more at the input. so you could regulate 12V AC/DC down to 9V DC, or 15V down to 12V.

By power transformer, do you mean it's a a self enclosed box that plugs into the power point, or the actual transformer component which you have to box yourself? Does it already supply DC? it would be a good and simple project.

[tranceracer]

yeah. definitely. build a regulator. for the power you want to output, you need a few volts more at the input. so you could regulate 12V AC/DC down to 9V DC, or 15V down to 12V.

Thanks for the regulator suggestion!  I found some simple power regulator circuits after doing some extensive digging thru the "web rotted" search.

By power transformer, do you mean it's a a self enclosed box that plugs into the power point, or the actual transformer component which you have to box yourself? Does it already supply DC? it would be a good and simple project.

Actually I found some 18VAC wall wart power supplies that someone was getting rid of.  I'm not sure how clean the output was since they were for old modems. 

Thanks for all your help Darren!
-tR

[darron]

there are some schematics/layouts on GGG to give you an idea of how to do it:
http://www.generalguitargadgets.com/index.php?option=com_content&task=category&sectionid=6&id=24&Itemid=26


you'd look at the regulated or ultra clean.

[tranceracer]

Yes, I came across the GGG regulator and it looks promising.

Thanks!
-tR

[squidsquad]

I've always had success using the advice of Craig Anderton = a 100 ohm resister on the *hot* side...followed by a 1000 or 2200 uf cap across the rails.  VERY simple & effective!

[freak scene]

I've always had success using the advice of Craig Anderton = a 100 ohm resister on the *hot* side...followed by a 1000 or 2200 uf cap across the rails.  VERY simple & effective!

so the cap goes from the + to the - of the adapter plug and the resistor goes in line between the + and the circuit board?

[squidsquad]

I believe the resistor comes first (from the transformer/adapter) & then the big cap.  Just in case Alzheimers has set in on me...it's VERY easy to 1: put your resistor in your *hot wire path*...2: connect the *-* side of your cap to the ground wire...3: touch the *+* leg of the cap to each side of the resistor & LISTEN.  One way...nothin will happen...the other way...the hum should vanish.  Then solder.

[Pushtone]

Yes, I came across the GGG regulator and it looks promising.

Thanks!
-tR

If you are looking at the GGG Ultra Clean PSU you might find the advice I got from Davnet interesting.
http://www.diystompboxes.com/smfforum/index.php?topic=62046.msg488783#msg488783
About adjusting the resistors Ra and Rb to get 12VDC out.
I used a cheapo 16VAC wall wart with it and it worked out well, although it gets very hot with that kinda of voltage drop and a 300-400mA draw.

[freak scene]

I believe the resistor comes first (from the transformer/adapter) & then the big cap.  Just in case Alzheimers has set in on me...it's VERY easy to 1: put your resistor in your *hot wire path*...2: connect the *-* side of your cap to the ground wire...3: touch the *+* leg of the cap to each side of the resistor & LISTEN.  One way...nothin will happen...the other way...the hum should vanish.  Then solder.

makes sense.  sort of like the power filtering in a tube amp.

i have an orange squeezer i just built and with a battery its dead silent but when i plug in my adapter (boss daisy chained off the tuner) it hums so loud it overwhelms the guitar completely. 

[Paul Perry (Frostwave)]

Note that if an 18V AC transformer is under no load, it could go up to over 20 volts, and when this is rectified you would get a peak voltage of 1.4 X 20 or more, that's almost 30V, so be sure to choose your filter cap accordingly, and realise how much power (current x voltage drop) is being dissipated in the regulator.

You can do it OK - I've done it myself - but don't under-rate anything.

[squidsquad]

I recall, "What's that smell?"  Then saw a little swirl of smoke coming from a tiny crack in a caps' top.  Looked like a live satellite shot of an erupting volcano.  Yep...the cap was too low of a voltage rating.