Wall wart noise reduction...will this work?

[Helmholtz]

How 5V?

[daz]

You said it would drop one volt for every 10 mA load and the 2 pedals together are 40 mA. So i assumed 4 x 1 v =4 volts. 9v - 4 v=5v.

[Helmholtz]

You said it would drop one volt for every 10 mA load and the 2 pedals together are 40 mA. So i assumed 4 x 1 v =4 volts. 9v - 4 v=5v.

I see.
So yes, 40mA will drop 4V.
If you lower R1 you will need to increase C1.

[daz]

But it doesn't drop. I finished it and it's not dropping. It works great too. I finished it and tried it flipping the switch back and fourth between battery and wall wart and nothing changes....LEDs remain the same brightness, tone doesn't change, and I can't even hear any hum unless i stop playing and put my ear to the speaker where i hear a tiny bit. So good to go !

[Helmholtz]

But it doesn't drop. I finished it and it's not dropping.

Then your actual load current must be much lower than 40mA or R1 is lower than 100R.
Ohm's law doesn't fail.

[daz]

I'm just going by the manufacturer's spec. They are behringer pedals and the UC200 chorus says 30mA, the TO800 which is a tube screamer clone i believe was under 10. You can D/L the specs on thier site but i have never seen a digital chorus thats much less than that, usually they're more. And screamers are generally around 5-10 mA.

[Helmholtz]

Use your DMM to measure actual supply current.

[daz]

Im not worried about it, works great regardless. If it were a matter of just touching the probes, but i'd have to pull the cover i made with all the components and unsolder things and much more to get the probes inline so i'll pass on that. But even at minimum according to specs of that chorus and the boss it;s a clone of, it would still be a total of at least 30 mA which would mean 6v, and i measure 9.6vdc at the output of the filter where it plugs into the first effect and turned on. So somehow it's not dropping voltage, surely not 3v let alone 4. I don't doubt what you said but theres gotta be some reason we're missing. But again, no matter.

[Helmholtz]

If it works for you - fine.

Current could be found from measuring the voltage drop across the 100R R1 from Vdrop/100.
But if you don't care, why should I?

Maybe your power supply input voltage is higher than 9V.

[daz]

It's 9vdc spec'd on the label, but like most it reads higher when not loaded, about 12vdc. But all wall warts i think are like that. At least the ones i recall measuring including the other one i tried to test the filter with because it had bare ends i could breadboard it with since i had no female jack.

[Chuck H]

I expect the 30mA indicated for that pedal is some "other" specification not related to current consumed in operation. Though I can't come up with just what. Sort of the way the back of some amplifiers indicate the wall AC power consumption in watts even though the actual amplifier power to speaker is also rated in watts (and always much lower). Sometimes laypersons would confuse the two.

[Mick Bailey]

It's 9vdc spec'd on the label, but like most it reads higher when not loaded, about 12vdc.

That indicates that the supply is unregulated. A regulated supply will read close to 9v with no load and keep that voltage under load. That will be the reason for the noise.

[Chuck H]

That indicates that the supply is unregulated. A regulated supply will read close to 9v with no load and keep that voltage under load. That will be the reason for the noise.

Though I could probably design and build a good 9V supply it's a little out of my wheelhouse. There are some designs on line but some pertinent info is a little vague. Maybe someone with more chops and confidence on the matter could post an affordable DIY build 9V regulated and clean power supply design. I know daz is up to building something. We've seen him do it

[daz]

Though I could probably design and build a good 9V supply it's a little out of my wheelhouse. There are some designs on line but some pertinent info is a little vague. Maybe someone with more chops and confidence on the matter could post an affordable DIY build 9V regulated and clean power supply design. I know daz is up to building something. We've seen him do it

I can build stuff all day long. I don't know theory at all but a schematic and rudimentary understanding of things is all you need as long as u r blessed with enough logic and common sense. Well, that and the internet's wealth of info and blokes like youse guys. In any case, I realized it's a ROLAND, not boss wall wart. I guess that explains it because roland mainly makes large gear like DSP's and keyboards etc, stuff thats big enough to easily fit regulation and filters inside them rather then making the wall wart huge. I suppose thats it anyways. It still hums a tiny bit, now even enough to matter really. But for the sake of making it as good as possible i will likely try my friend's Behringer wall wart since my 2 pedals are Behringer and if it's even quieter i'll just get one of those. Like i said, i built this little board with two 9v battery holders and a switch that goes between battery power and wall wart. So I don't really *need* a WW really since i have some very high end rechargeables. But i play at home about 95% of the times so a WW means no need to flip a switch to turn the batteries on and off every time i plug in. (which can be s many as 10 times a day or more. 9V power jack is just left of the switch and i fit the filtering inside that little housing too.......

[Mark Hammer]

The thing about DC is that the criteria for being DC - as opposed to AC - are pretty darn loose. All that's required is that the output not include any negative component. As long as everything it provides is some level of V+, it's considered "DC". The second problem with wallwarts in particular is that they are generally sealed black boxes, such that one can't see what's inside them, from the outside, OR by unscrewing them. I recognize the very legitimate concern that giving a novice access to the inside of a device with a direct connection to wall current is an extremely dangerous proposition. So the fact you can't take them apart, for a preview of what to expect, but MUST rely on measured or heard ripple, makes sense from a safety perspective. But you would think that there might be some sort of code on the sealed module that might convey something more than simply voltage, current and which contact is positive and ground.

Have there been attempts in past to classify adapters into categories/degrees of regulation that consumers could look for on the sealed black module, but either floundered or were interfered with by industry advocates? For instance, let's say there were 5 "levels" of DC regulation, according to circuit parameters (which would encompass both switched and "regular" supplies) and amount of resulting ripple. A manufacturer could then instruct consumers of their product to use "Level 3 or better" or something like that.

I mean, it's nice that such problems as began this thread result in "spreading the gospel" of how circuits work and could be improved for end-users. But it would be better if the industry made the job easier for consumers. This complaint is coming from a guy who dates back to the time when the same wallwarts used to power desktop calculators were being applied to powering pedals.