Power Filtering

[soloarchitect]

Ok, I have built a few pedals on my own, I am fairly knowledgeable about the basics of electricity and names of basic components and how they work etc, many of the concepts however, I have yet to fully grasp.  I have read many topics on many different days and I have a pretty busy life and tend to forget stuff I learn unless I get to practice it, which unfortunately I don't as much as I would like because of work, single parent with half custody and being on call the other half.......I want to learn how to remove noise from signals, power and line input....When I read from searches, I start to think I am getting somewhere, then I either get tired, or have to move on to something else, or just get lost in all the possibilities suggestions and discussions and seem to be getting nowhere with this. I have several questions, which I am sure many have been answered on this forum.


1) I am looking for the names of the components needed to build this..... I plan on putting two batteries on a rolling cart, equipped with a pcb that can charge each battery, there are also outputs on the battery that are converted, one will

run a 110v ac input guitar amp, that is rated at 30watts(I would also entertain the idea of running safely, 2-3 amps totaling 300 watts stated power, I would also run about 10 effects pedals. What I would like this system to do, is use one

of the batteries to generate the inverter, voltage regulator filter systems to give clean power, and as the voltage on the battery falls below a selectable thresshold that would start to create issues on performance, it instantaneously

switches to the other battery smoothly with no clicks or pops, and then charges the depleted battery back to full charge, when the threshold of the battery is detected at maximum charge, the charging process halts and waits until the

second battery needs charging. The idea here is to have smooth clean power that is portable. I am sure this would be fairly expensive, but it would be pretty damn cool and handy.



2) Typically anywhere I go to play have old wiring with only + and - the third prong might be present but it is almost NEVER hooked up. Therefore I always have noisy power going into my pedals and amp, looking for recommendations,

FIRST, I would like to know what I could do to filter the power coming in from the wall. SECOND, if I have an existing wall war like a 9v I-spot, is it possible to make a simple effective filter to bypass noise from its output before going into

a pedal? Also, I realize my guitar will pick up noise and that is a whole different story, but as it goes from one pedal to the next, my signal seems to be picking up noise, is there a standard scheme of cap/resistor that I could solder inside

each pedal from the input or output jack that would reject the buzzy noise that tends to occur(this is not hum, it is a higher frequency buzz sound that is much louder when I turn on a high gain pedal)....I have heard of buffers helping with

this etc. As I have said, I have read many topics but was hoping there were simple straightforward DIY reference for a technique/system with formulas to determine what to use to cancel out trash in my power and input signals.



3) I saw a link to weber transformers to use one transformer to build a Spyder, from R.G.'s Geofex site. I read another post a few weeks back, there was another brand that looked even more appealing, all I remember is they looked real

nice and the metallic hunk on the transformer was a dark blue finish, I am looking for that brand name? I plan on building this for the pedals but still would like to understand the concepts to number 2 for educational purpose


I realize I am asking a lot, and it isn't all that simple and there are many factors that I have to determine myself to know what to values and/or components to etc,etc,etc. but if anyone can chime in on anything without going through much trouble, I would really appreciate it. Thanks.

[R.G.]

1) I am looking for the names of the components needed to build this..... I plan on putting two batteries on a rolling cart, equipped with a pcb that can charge each battery, there are also outputs on the battery that are converted, one will

Question 1, and probably the most important one to what you want to do: how big/heavy can you stand the batteries to be?

There are a lot of other details that can be worked, but from an energy standpoint, if you can't store enough energy, you can't get it back. Can you, for instance, use two 30-pound automotive batteries?

run a 110v ac input guitar amp, that is rated at 30watts(I would also entertain the idea of running safely, 2-3 amps totaling 300 watts stated power, I would also run about 10 effects pedals.

A solid state amp rated at 30W probably wastes another 30W as heat unless you use a Class D switching amp. Then it wastes only about another 3-8W as heat. So you need to pull 35-60W from the batteries through the inverter. The inverter is a switching device that wastes about 10% of the power as well, so the power pulled directly from the batteries is on the order of 40-66W for this scenario.

If that's coming out at 12Vdc nominal, it's on the order of 4-5A while you're doing it. Since music typically has a 20db crest factor, you're not doing this all the time, so while there are peaks at 4-5A, the average is probably more like 1-2A. (as you can tell, without knowing the exact amplifier and conditions, there is a lot of guessing and assumptions to use here.)

So call it 2A average, to be conservative. Each hour uses 2 Ampere-hours (which is how batteries are rated). A 12V sealed lead acid battery rated for 12A-H costs on the order of $40. One rated for 18-20 A-H costs about $60. That's 4-6 hours or 8-9 hours if you run them all the way down between charges.

... which is a bad idea. They wear out fast that way. They'll last longer if you cut that in half, so a $40 sealed lead acid would give you a couple of hours, a $60 one 4-5 hours. Single sealed lead acid batteries are available up to about 200+ A-H for $300-400. Pick your time and poison, being aware that you want to buy two of them. Car batteries are more A-H and cheaper, but spillable. Deep cycle marine batteries are expensive, but big capacity.

300W of amplifiers needs 10 times the battery A-H for the same time, or play 1/10 as long for the same battery capacity.

What I would like this system to do, is use one of the batteries to generate the inverter, voltage regulator filter systems to give clean power, and as the voltage on the battery falls below a selectable thresshold that would start to create issues on performance, it instantaneously switches to the other battery smoothly with no clicks or pops, and then charges the depleted battery back to full charge, when the threshold of the battery is detected at maximum charge, the charging process halts and waits until the second battery needs charging. The idea here is to have smooth clean power that is portable. I am sure this would be fairly expensive, but it would be pretty damn cool and handy.

I'm not aware of such a device commercially. It may exist. I recently designed a solar battery charger with a pot full of "if voltage is under/over X then do Y" conditions. One microprocessor, a few MOSFETs, and A Simple Matter Of Programming. It can be done. You might have to hire someone who understands batteries, microprocessors, and analog electronics.

However, if the battery cart has a line cord to charge the batteries and you can plug it in to charge the backup battery while using the primary, it's simpler to use the wall power, and cheaper.

2) Typically anywhere I go to play have old wiring with only + and - the third prong might be present but it is almost NEVER hooked up. Therefore I always have noisy power going into my pedals and amp, looking for recommendations,
FIRST, I would like to know what I could do to filter the power coming in from the wall.

A 300-500W ferroresonant (also called constant-voltage) transformer is an amazing power filter. What goes is can be rough, but what comes out is pure. They're heavy, but not ridiculously expensive.

SECOND, if I have an existing wall war like a 9v I-spot, is it possible to make a simple effective filter to bypass noise from its output before going into a pedal?

If you're using a 1Spot by Visual Sound, a whole lot of work has already gone into making that output quiet already, and there's some fairly sophisticated filtering already there. For other single-place wall warts, I'm not so sure, and I hear different things. For wall warts without much filtering, something can be done. A lot depends on what kind of noise you're getting and where's it's coming from. It may not be the power system.

Also, I realize my guitar will pick up noise and that is a whole different story, but as it goes from one pedal to the next, my signal seems to be picking up noise, is there a standard scheme of cap/resistor that I could solder inside each pedal from the input or output jack that would reject the buzzy noise that tends to occur(this is not hum, it is a higher frequency buzz sound that is much louder when I turn on a high gain pedal)

It's nearly always a good idea to put a small resistor in series with the incoming +9V power and a large capacitor, 100uF to 1000uF across power and ground, and parallel that last capacitor with a 0.1uF ceramic capacitor. It certainly won't hurt, and may help *if* the source of your noise is the power system.

....I have heard of buffers helping with this etc.

That's unlikely. A buffer will help with loss of treble from the pickups' high impedance and any cabling losses, but buffers are not a good way to reject noise from up stream. Putting a buffer out in your guitar may help. Maybe. Depends on the source of the noise. Gotta find that before any bandaids are likely to be effectively.

As I have said, I have read many topics but was hoping there were simple straightforward DIY reference for a technique/system with formulas to determine what to use to cancel out trash in my power and input signals.

The key is to find the source and not pick it up to start with.

[soloarchitect]

Thanks R.G.! I am sure you have a donate button somewhere, and I will use it to show my appreciation, of course the donation is not directly proportional to how much I appreciate knowledgeable persons like yourself and sites like this, and esp. this one!  You have always been willing to take time out to answer others questions and are very thorough and detailed with your explanations. Of course I have already donated to this site in the past and plan on doing so in the future.