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Build A Power Supply For Your Guitar Pedals

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If you're like me, you know how annoying it is to use up 9V batteries on your guitar effect pedals.  Its wasteful, and brand name 9V's are almost $9 for a two-pack.  If you forget to turn off your pedals you've thrown away big bucks.  Its an extreme waste of money when you can build your own power supply for only about $25.The power supply I designed and built delivers steady, regulated 12 volts, 9 volts and 5 volts all at the same time.  Each voltage has two outlets, but they can be "daisy chained" with a custom cable to connect many more pedals.  The styling is an homage to the old days of vacuum tubes, when components generated so much heat they needed to be on the outside of the casing instead of inside.  I used some gigantic capacitors that I thought would look cool, other than that they are major overkill. In this Instructable I am going to assume that you know some basic electronic skills and know what I am talking about when I say capacitor, resistor, LED, transformer, AC and DC, etc.  There are lots of introductory electronics Instructables and soldering Instructables you can check out if you'd like to gain a better understanding of basic electronic principles and components.IMPORTANT NOTE:  Depending on what pedals you intend to use this for, you should take care to wire the DC connectors as pin-positive/ring-negative or pin-negative/ring-positive.  The latter is the industry standard way of doing it, although it poses issues when building a pedal that has a metallic housing.  I prefer pin-positive/ring-negative because of that issue, and I wired this supply in this way.  Please take care as to which way you wire the power supply to prevent damage to your pedals.
 
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Hey Matt! I know its been a few weeks since I was on here asking questions! I had a couple more if you don't mind. I'm in the process of ordering everything from DigiKey now...

First, you said something about I could put an EMI filter on if I wanted...can you recommend one for me?

Second, a goofy question! I know they shouldn't under normal circumstances, but what happens if one of these components fails? Will the voltage regulators prevent damage to the pedals?

mattthegamer463 (author)  shoelesscraig21 days ago
I often use these: http://www.digikey.ca/product-detail/en/15SRB8/CCM1773-ND/1306107

There isn't much bad stuff that can happen with this simple supply, but the linear regulators are basically a resistor in series with the load and a zener diode that clamps the output voltage to a certain level.


Best you could do is add a fuse in series with each output to prevent excessive current being delivered to the pedal, but that doesn't protect against excess voltage. The fuse rating should be around 50% more than the pedal operating current. A resettable fuse like Digikey BC2719-ND might serve well for output protection. This is probably the kind of thing production units have in them to prevent short circuits and damaged pedals from damaging the supply.
spunko2 months ago

Hello, I'm willing to build this power supply to power 10 to 15 pedals, they all are center negative, 9v (mostly BOSS), and I don't want to buy a voodoo or cioks PSU, they cost like $200 USD. Do you think this will work as those PSU? Will it add noise to the sound signal?. I know a noise gate is usefull but I have used 9v adapters that add a lot of noise even with the noise gate. Sorry for my bad english.

mattthegamer463 (author)  spunko2 months ago
To be honest, if you just want to get it done for cheap, find a good low-noise 9V wall adapter from a guitar store and buy one of these online: http://www.ebay.ca/itm/1-To-8-Daisy-Chain-8-Plug-Cable-DC-Connector-For-Boss-Roland-Dunlop-JOYO-MOOER-/321105607281?pt=Guitar_Accessories&hash=item4ac362ba71

Also, if you're having trouble with noise, read up on "ground loop hum" and keep away from noise-emitting things like electric motors and CRT televisions.
Thank you for your response. Actually I wanted to buy a 1spot adapter, unfortunatelly in my country it cost $50 + taxes, I live in south america. If I build this unit, I know it will be chaeper, and of course a lot of fun.
The cheap adapters here are not regulated, and 90% of my pedals are voltage sensitive. One time I tryed a cheap one and it damage one of my boss dd3.
Maybe I can get this cheap adapters, open them, and Make them regulated with this tutorial, like a cheapo 1spot clon.
What do you think?
Thank you for time!
mattthegamer463 (author)  spunko2 months ago

You don't even need to open it. Two caps and a regulator connected to the output connector and you're all set. You could regulate it, then connect to a daisy chain cable and run 4 or 5 boss pedals on a single adapter without issue.

Hello, I'm sorry, I know its been a while, but could you help me with an schematic or link where I can get a guide for this regulator. I got two cheap 9volts 500 mAmp.I used my fluke multimeter to measure voltage and both are giving 15/17 volts, if I use them with my pedals, they will die :(

mattthegamer463 (author)  spunko28 days ago

Sounds like they are unregulated supplies. They will output 9V when the load draws 500mA but a higher voltage if the load draws less. With no load (ie. when measuring with a DMM) you'll see the highest possible voltage. You could test by finding out how much current your pedal will draw, then calculate a resistor to use as a dummy load on the supply. Put the resistor across the supply and measure, and measure the voltage across the resistor. That will be the voltage the supply will drop to when hooked to your pedal.

Or, make a regulator. As long as you don't draw too close to 500mA the regulator will have enough voltage overhead to function.

Datasheet for 7809 - 9 Volt linear regulator

http://www.fairchildsemi.com/ds/LM/LM7809.pdf

Page 18 Figure 6 shows the simplest application of the regulator possible. Hook it up and give it a try.

I'm sorry for the double post. I have found two printer PSU from my old stuff. On the cover it says output 13.5Vdc / 1A, they look the same, but one gives 18v and the other one gives 9v. I opened them apart and they are almost the same, but the one that gives 18v it has only two diodes, on the other hand, the 9v it has 4 diodes like I'm used to see, besides that, they look the same.

Do you think I have to add the two diodes missing on the 18v PSU?

It will be better live the PSU like that, and just focus on the regulator?

What happens if I use a 9v 200 mA supply? it will give regulated 9v, but the same 200 mA?

Sorry to botter you!

thank you very much

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mattthegamer463 (author)  spunko27 days ago

Two diodes form a full-wave rectifier, this is for transformers that have a center tap. Four diodes form a bridge rectifier, for an untapped secondary coil. Now in the pictures you showed they do not have any regulation, so the voltage will vary depending on the current being drawn by the load. Why they both say 13.5V on the outside and one is showing 18 and the other 9, I would guess that the one showing 9 is broken. 18V sounds about right for an unloaded 13.5V transformer.

Thank you very much. I want to make a regulator with the 7809 so I can use it with at least five pedals, if I use this supplies and make the regulator, the output will be the same 9v 500 mA, but this time steady 9v?.

What happens if I use a 9v 200 mA supply? it will give regulated 9v, but the same 200 mA?

I'm sorry for my english.

Hello,

I'm trying to build one of these for my pedal board but I need to power 16 pedals and I'd prefer to have separate isolated outs for each rather than daisy chaining them (some are pin positive and others are pin negative). Do I have to change the number of capacitors or anything else to do this?

Also, I'd like 2 of these outputs to put out 18V for extra headroom in certain pedals. And I'm having trouble finding an enclosure that has a square hole for the IEC connection. It's cheaper for me to have a regular sized dc in (just like on the tops of pedals) so I'm going to do that. Will these two things mean I have to change the values of the transformer or fuse or anything else in the circuit? I may have to run the unit off a regular 1 spot 9v 1700ma power supply. Can I still get 18V out of two of the outputs or do I need to use some different kind of power supply?

Thanks,

Stefan

mattthegamer463 (author)  stefanrichter28 days ago
Hey, this supply doesn't have isolated outs (all pedals have common negative power connections) if you want isolated outs, you'll need to get a special transformer with many output taps, which are hard to find. To be honest, I recommend you just buy one. You can't get 18V out of a 9V supply without a voltage multiplier circuit, which will add unwanted noise.
You're right, I completely forgot about going from 9V to 18V.

Okay you've been super helpful and I hate to ask you this, but do you mind pointing me toward a heat sink that you would choose? I've never bought one before and I don't really know if there's a specific kind that I'm supposed to use.
mattthegamer463 (author)  shoelesscraig1 month ago
If you got the space, Digikey # HS350-ND would be pretty good. It says its good for 10 watts at 50 Deg C so you could probably put one reg on each side of it. You'll need to use some thermal grease to get good heat conductivity between the heatsink and the regulator, too.
Hey Matt, after doing a little more in-depth figuring, I think I'm guessing too high when I said 2A-3A. I actually researched and added up my current draws, and I'm actually going to be pulling more like 1 amp. And that is with everything on (and of course I'll never have every pedal on at the same time). So my question is this... Most of the transformers around the size that I need are all about the same price. That being said, should I just stick with the one that you told me about? Or is it going to provide too high of a voltage if I'm not pulling the entire 2-3A?

Also if I wire that transformer in parallel it can give me 2.78A, but if I wire it in series it's good for 1.39A. Does the voltage situation get better if I simply wire it in series? I just want to make sure that I'm not providing the voltage regulators with too much voltage when I'm pulling little to no amperage. Since I believe you're a guitar player, you'll understand that a lot of the time I'll only have one pedal on, or sometimes none at all.

Or am I looking at this all wrong?
mattthegamer463 (author)  shoelesscraig1 month ago
If you wire that one in parallel you get 9V at 2.78A, if you wire in series, you get 18V at 1.39A. I would use that transformer anyway. Spread your load across several regulators so they aren't being too heavily loaded each, and hook them all to a heatsink. You can always tweak the cooling later if its not enough.
mattthegamer463 (author) 1 month ago
Hi, its possible to do (but not with this design as-is) but you should not modify or mess with the 6.3v AC output as it is for powering the tube filaments. Most tube amps are unregulated and so a change in current draw on the transformer can have adverse effects. Also there are lethal voltages in there so you shouldn't be messing around with those anyway.
Hey Matt, where did you get the DC jacks and plugs from? I looked at DigiKey (but maybe I'm looking in the wrong spot). I would love to have the plugs in right angles if possible.
mattthegamer463 (author)  shoelesscraig1 month ago
Hey check out digikey part CP-102A-ND or SC1330-ND.
I really need help! I'm trying to build a 12v output into my amp head to run a 12V (Im presuming DC) led strip off, I have a 6.3V AC connection available on the transformer, would this design be usable to get 12V out somehow?
One question about the transformer. I see that the one you suggested is a 2.7A on the secondary. So am I understanding correctly when I say that it will provide 9v even when the current gets to that 2.7 range?

As far as capacitor voltage ratings go, I just need a minimum rating of 12.7v, correct? Since I am not using any voltage higher than that? Or does the rating need to be higher to account for something else I'm not thinking of?
mattthegamer463 (author)  shoelesscraig1 month ago
For your first question, yes you are correct.

Capacitors should be over-rated by at least 100% at low voltages. When capacitors are under-rated, they explode in a very ugly way. 25V caps are definitely a good idea. 50V are even better, but for high values they start getting pretty big.

The ones I used were 50V 10000uF. Pretty big but no worries about them exploding.

I'm having a hard time finding a 120v to 9v transformer for this. Any chance you give me a pointer on where I might find one?
mattthegamer463 (author)  shoelesscraig1 month ago
http://www.digikey.ca/product-detail/en/VPT18-1390/237-1323-ND/2090061

That's what I would buy.
Okay so I could use exactly the same capacitors for C1-C3 that you used and work great. I like the look you went for. On the schematic C4-C6 are listed as 100uF, but in your last post, you said 100nF. Which is correct?

Also, do they make LEDs that work on 9V? That way I wouldn't have to create 5V power for the indicator? And if they do, what size should I make the resistor for it?

Sorry for all the questions. I really appreciate your guidance!
mattthegamer463 (author)  shoelesscraig1 month ago
Sorry, in the 4 years since I did this Instructable I've learned some things. 100uF works but is excessive. In fact it is less ideal than something lower to prevent oscillations on the regulator output. So use a 100nF instead. They're also cheaper and have a much longer lifespan.

LEDs only use between 2V and 3.3V, there is no such thing as a "9V" LED. That's just an LED with a built in resistor, for 10x the price. Basically, since the diode wants something like 2V, giving it 9V makes it blow up. The key is to limit the current it can use by adding a resistor. This resistor passes the LED's current and in the process the voltage will drop down. You pick the right resistor that gives the LED enough voltage and current to light up, but not so much it burns out.

for 9V supply and 2V LED, we need to drop 7V across a resistor. A typical current level is 10mA or 20mA for an LED. The little cheap red ones usually want about 10mA. So, R = V/I which is 7 V / 0.01 A = 700 ohms. Lets call it 820 ohms, the nearest standard value.

Use this website (http://led.linear1.org/1led.wiz) to calculate them for you when you're in a hurry. Its helpful because you should technically also calculate the power the resistor will have to dissipate, as if it is too high the resistor might burn out. In this case, 10mA and 7V = 70mW of power, well below the 250mW a "regular" size resistor can dissipate without excessive heat buildup.
Man, you're awesome! Thanks for the reply!

Okay I see on your schematic six capacitors C1-C6. When you say that I will need at least 2 -4700uF caps, where on the schematic do you mean? Where C1-C3 are, or do you mean the ones next to the voltage regulators? Also when you say "at least 4700uF" is it okay if I go bigger? Or is bigger a problem?

I want everything to be very quiet as far as noise goes, I just don't want to go too overkill for no reason. How do you think the noise of this thing compares to a voodoo labs?
mattthegamer463 (author)  shoelesscraig1 month ago
I was referring to the caps C1-C3, which are 10000uF on my schematic. Those are indeed overkill but they look super cool so that's why I used them. C4-C6 (on the regulator output) should only be about 100nF as they just prevent the regulator from oscillating under certain conditions.

Since Voodoo labs is probably a switch mode supply (I could be wrong) this power supply should be inherently less noisy. As long as you don't wrap any of the AC wires around any of the DC wires, you should not have noise problems. An EMI filter on the inlet will help with any noise from noisy devices you may have plugged in around your house. I didn't use one and I still didn't have a problem. Ground loops are the major source of noise, not the supply.
Matt, awesome looking power supply! I have a quick question for you. I need to build one of these to only power 9V pedals. So do you recommend I buy a transformer with 9V or 12V secondary? I would like the total 9 VDC output to be able to do about 2-3 amps (I have quite a few pedals). This being said, do I need to buy different regulators and rectifier than you used, or will the ones you chose handle that much current? Also am I thinking correctly when I say that my transformer will only need to be good for 3 amps on the secondary side?

Sorry for all the questions but I'm an electrical guy not an electronics guy so this is not really my strongest point! Any help you're willing to give me would be awesome!
mattthegamer463 (author)  shoelesscraig1 month ago
Hey there, so basically, transformers essentially deliver a certain amount of power (in watts) which is referred to in transformer-speak as Volt-Amps (VA). The reason for this is a little complicated but basically, when a transformer says "9V 100mA" it means "output is 9V RMS when the load is consuming 100mA" and so a lighter load will cause the voltage to rise above 9V and more load will cause it go drop below 9V.

This is an issue when using a simple regulator like a 7800 series. They function by taking in a voltage and outputting a lower voltage, but the same current goes in as goes out. The rest of the "voltage" is wasted as heat. If you put 30V into a 5V regulator, the efficiency is 5/30 * 100 = 16%, at any load. Not very good. The idea here is to get only a couple volts above 9V so that the regulator can give you a steady 9V without having to waste too much power and generate too much heat.

a 9V transformer that you would be loading correctly at the higher current levels (a 4A transformer should give a little more than 9V at 2-3A of load) should be what you want. Thats 4A on the secondary side, by the way. Most transformers are listed by their secondary characteristics and their input voltage, but all transformers are about the ratio of turns between the primary and secondary coils. A 9V 4A transformer won't use much more than a quarter amp on the primary. 9V RMS when rectified and smoothed with capacitors turns into about 12.7V DC, which is lots for a linear regulator. Big caps and some current overhead help keep this voltage up high even with a high load of pedals.

Once you have rectified the 9V AC from the transformer and smoothed it with some capacitors, you'll have something like 12.7V DC. This can then be connected to several regulators in parallel. You can set it up to run two or three pedals per regulator so there won't be excessive heating of the regulators even if your input voltages are a little high.

That overs the transformer and regulators. The caps you'll need should be pretty big, at least 4700uF I would guess. A couple of those at least. If you are concerned about rectifiers, you can purchase four rectifier diodes which have a maximum forward current in decent excess of 3 amps (say 6 amps) and arrange them in a bridge rectifier configuration yourself without much trouble. Alternatively, large metal brick-like ones can be bought at surplus stores which can handle far and beyond the current you require.

Since you're an electrical guy, just keep in mind that everything is just an extrapolation of Ohm's law. Understand that and anything can be achieved.
garykliz3 months ago
Hello, I am currently gathering up parts for this as I need both 12v and 9v DC outputs... don't need the 5v. I would like to completely enclose mine and not have them outside of the project box like yours. Do you have any recommendations for that?
mattthegamer463 (author)  garykliz2 months ago
The AGL1218 should work great. I added the regulators to the list. Thanks for the tip.

Hello, sorry to be a pain, i dont see the regulators in the list and i checked it twice! Also what is this guy http://cdn.instructables.com/FL3/58T4/G4PBTA41/FL3... ?

I would like to use a metal housing so from reading it sounds like a EMI filtered IEC is necessary... anything else to do to use this inside an aluminum housing?

Also, my two 12VDC pedals both require serious current when compared to the other smaller pedals. (Markbass pedals) one will draw up to 550mA and the other 600mA. Should I dedicate one regulator circuit for each 12VDC output?

mattthegamer463 (author)  garykliz2 months ago

Sorry the change didn't stick. I added it now for sure. I don't think an EMI filter is required but it definitely never hurts, make sure to hook the earth ground to the aluminum chassis for safety. For those high-current pedals I would use a separate 7812 regulator for each, and add a heatsink too. You can also bolt the regulators to the aluminum chassis to dissipate heat too.

If you are curious about how many watts of heat they'll produce, you can calculate it by taking the input voltage and subtracting the output voltage of the regulator, and multiplying it by the current draw.

mattthegamer463 (author)  garykliz3 months ago
Putting the items inside the enclosure is as easy as putting them in there! Just mount them so that they won't ever move and touch anything, as you don't want things shorting out in there. Don't forget a fuse for fire and human safety.
Thanks... was wondering in regard to any heat if it would get too hot inside. Also, what gauge wire did you use, and are these capacitors adequate? http://www.taydaelectronics.com/100uf-50v-105c-radial-electrolytic-capacitor-8x11mm.html?gclid=CKXpo8GBybsCFUiEfgodUksA2A
mattthegamer463 (author)  garykliz3 months ago
The heat shouldn't be an issue. If you notice it getting really hot you can always add some holes to vent. 20-22 gauge stranded wire is a good choice. Those caps looks fine.
Thanks for the help. I plan to use a metal case of some sort, probably aluminium and would like to replace the "flip" style toggle switch with a "stomp" style one to make it a bit more functional.. Is this easy to integrate into your schematic?

image of stomp switch http://tinyurl.com/kobp2r7
mattthegamer463 (author)  garykliz3 months ago
For the enclosure, make sure you have connected the green ground wire to the chassis, for safety.

To integrate a switch like that, be sure it is the "click on, click off" type. If it is rated for 125V AC it can be used in series with the primary of the transformer. That is the best way to do it.
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