Instructables
Picture of 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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Step 1: Planning and Schematic

The first thing to do is design the circuit.  Many guitar pedals and stompboxes have 9V DC power jacks on the back (if your's doesn't and you're feeling ambitious, you can add your own) which we will use to power them instead of the 9V internal battery clip.

The schematic I designed can be modified for whatever voltages you would like.  For example, if you don't have any 5V pedals, you can just swap the 5V power regulator for a 9V regulator, and now you'll have double the 9V power.  

The schematic uses a simple power supply circuit converting AC to pulsating DC, smoothing it with capacitors and running it through voltage regulators for fixed DC outputs.

Here is a higher resolution version of the schematic if you can't read the one below very easily:

http://img.photobucket.com/albums/v321/mattthegamer463/Schematic.png

Step 2: Parts and Tools

Parts:



- 5" long by 2.5" wide by 1.75" tall project box

- Segment of stripboard, veroboard (it's like perfboard but the copper is in strips, see pic)

- 7809 (9v) and/or 7812 (12v) linear voltage regulator(s), depending on the voltages and configuration you want

- 18V Transformer

- Bridge rectifier

- IEC Power connector

- Two 10000uF 50V capacitors (less overkill version: 100uF)

- Three 10uF 63V capacitors

- Toggle switch

- Green LED

- 5mm LED holder

- 220 ohm resistor

- Fuse holder

- 100mA fuse

- Six 2.1mm DC jacks

- Six 2.1mm DC connectors

- Adhesive rubber feet

- Wire

- Solder

- Assorted nuts and bolts

- Small segment of aluminum

- Masking tape

- Electrical tape



Tools:

- Drill and bit set

- 1 1/4" hole saw bit

- Hot glue gun

- Soldering Iron

- X-acto knife

- Wire strippers

- Wire cutters

- Square

- Ruler

- Flat file

- Vernier

- Multimeter

Step 3: Drilling and Cutting

Short version: 



Cover in masking tape, mark hole locations, drill pilot holes, drill appropriate sized holes using pilots as reference.



Long version:



I did the layout freehand, marking the middle of the box using the square, and just measuring and sizing up locations using the components.  To make it easier to write on the box, cover it in masking tape.  Use a sharp pencil so that you can get accurate markings and can erase if you make a mistake.  Take your time and get it right, theres no turning back once you start drilling.



Use a  1/8" or 3/32" drill bit to drill pilot holes at each hole marking.  For the IEC connector hole, drill in each corner of the rectangle.



After I drilled pilot holes in the corners I used a 1/4" bit to drill around the perimeter of the rectangle, being careful to not pass over the edges.  Then, I used some pliers to snap the remaining plastic out of the center, and used the flat file to file it into a rough rectangle.  Keep filing and test fitting the connector until it fits snugly.  Be careful with IEC connectors that have pop-out flanges to lock them in place, since those are most likely designed for metal enclosures and thick plastic may prevent them from locking in place.  I had to switch for a connector that had mounting screws because of this.  Once the connector is in place, you can drill holes for screws or bolts/nuts with no problems.



The rest of the holes will need to be drilled appropriate to the bolts you've selected for mounting your transformer and the diameter of your capacitors.  My capacitors were 30mm diameter, so a 1 1/4" drill (about 32.5mm) worked great.  The diameter of most DC jacks is about 8mm, but check with a vernier before you drill.



The aluminum plate that goes over the DC jacks is 4" long by 1" wide.  I used a 5/16" drill bit for the holes on it, spaced 5/8" apart.  You can use the bastard file to remove the sharp corners, and some 120 grit sandpaper to smooth the edges and give it a brushed look.  I used 4.40 threaded hex head screws to secure it in place.




Step 4: Circuit Building

Short version: 



Build the circuit, remember to cut the rails on your stripboard to separate segments.



Long version:



 Now that the chassis is sorted out, the next phase is wiring up the circuit board.  Measure the inside of the project box and determine how much room you can use for the circuitry.  I used a piece about 2" by 2.5" and it fit great and was still easy to populate with components.



If you don't get a pre-cut piece of that size, the easiest way to cut it without using power tools is to score the edge to break it at with the x-acto knife, then break it over the edge of a table, holding both sides of the break firmly.  You may need to break off more than you want with the first break.



To cut the traces on a stripboard, you can use a drill bit held in your hand and just turned into one of the holes until the metal is scraped away and broken.  A close-up picture below shows the result.



I didn't have a plan going into this, but I basically just set up + and - rails and lined up the regulators on them.  The regulators all use the input voltage from the transformer (18V AC ends up being around 28V DC) and common grounds, so they can be placed in a line, and then the output pin connections can be cut with the drill bit.



I wired the large capacitors off-board because I wanted them to protrude from the top of the chassis, and they just take up too much room on the PCB.  



Solder the 220 ohm resistor to the LED.  Then solder wires to the resistor and LED and connect the positive wire of the LED (the longer leg) to the output of the 5V regulator and the negative wire to any negative point on the board.  



Testing the circuit is difficult, so just triple-check that everything is correct.  Before you turn it on use a multimeter to check for shorts between ground and the input voltage, and check each output voltage with the input voltage and ground to make sure nothing is shorted out and would cause damage. 






Step 5: Assembly

Short version:  Put it together.



Long version: The best components to start with are the DC jacks.  I used hot glue to hold them in place because the threaded portions weren't long enough to reach through the plastic and the aluminum and still have room for a nut.  Make sure that they are all aligned straight ( I messed this up) so that they will be easier to wire up.  Use lots of hot glue to make sure they won't get pushed in when being plugged into.



Next, install the transformer, fuse holder and IEC receptacle.  Use nuts and bolts for the IEC and the transformer, and use the nut supplied with the fuse holder to fasten it in place.  Also put the toggle switch in place so that you can wire up the AC portion of the circuit before the big caps and board get in the way.



That being said, now is a good time to wire up some more of the circuit.  Solder one wire from the primary (120V) side of the transformer to one of the locations on the back of the IEC receptacle.  The two that are next to each other are the Live and Neutral, the other lower one is the Earth which we won't use since this is a plastic housing.  Connect the other wire from the primary side of the transformer to the fuse holder, then solder a wire from the fuse holder to the toggle switch, and from the toggle switch back to the remaining connection on the IEC receptacle.  The chain should be:



IEC -> Transformer -> Fuse -> Toggle switch -> Back to IEC



Now that those are in place, put in the circuit board and caps.  To affix the capacitors, I put a zip tie around each one, and then rested them inside on the zip tie, and glued them in place.  




Step 6: Assembly Continued

Solder the wires from the secondary side of the transformer to the AC input pins of the rectifier on the circuit board.  



To hook up the DC jacks, cut nine pieces of wire about 1" long.   Solder wires from the center pin of Jack 1 to the center of Jack 2, Jack 3 to Jack 4, and Jack 5 to Jack 6.  With the remaining 1" segments, daisy chain wire to a remaining pin on each jack.  This will link all the negatives together. 



Cut four 3" segments of wire.  Solder one end of each to the 12V regulator output, 9V regulator output, 5V regulator output, and a common negative point, respectfully.  Then solder the other ends to a center pin of a 12V jack, a 9V jack, a 5V jack, and the daisy-chained jack negatives, respectfully.



Put the LED holder in place, and snap the LED in. 



With the board up away from the jacks, make sure there are no short circuits, especially on the AC side of the circuit, and then carefully plug in the power supply and see if it works.  Use a multimeter to check that there is 12V at the 12V jacks, 9V at the 9V, etc.  The LED should light up.



BE EXTREMELY CAREFUL AS YOU HAVE LIVE EXPOSED 120V WIRES THAT COULD ELECTROCUTE YOU VERY EASILY.



Next, put some electrical tape across the DC jacks so that nothing on the circuit board can touch them and short out.  The metal plates on the regulators are connected to ground and will short out anything they touch.  Also tape the pins of the capacitors and around the 120VAC connections for safety.



If everything works great, bend the circuit board back into the case.  A nice touch would be to put some two sided tape on the back of it and stick it to the inside of the cover plate.  Screw the box shut.

Step 7: Finished!

Picture of Finished!
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You now have your very own guitar pedal power supply!  Use it to run your pedals without having to waste batteries and streamline your pedal board or setup without needing several DC wall adaptors.



The beauty of this design is it is very customizable and expandable.  If you include a center-tapped transformer you can add negative voltages to power some elaborate homebrew pedals or amplifiers.  The possibilities are endless and this is a great starting point. 



I hope you liked my Instructions.  They're a little long in the tooth but I wanted to make sure that the maximum amount of information was available with minimal misinterpretation.  Please leave a comment if you have any questions or thoughts.



Thanks for reading!





Matt


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JohnF71 month ago

ahhmm, i dont get it. im sorry, you have used 18v transformer right? so, i will remove the transformer there in your tutorial and replace a transformer that can work at 220v ac? im sorry man, i am confused.. by the way im from Philippines. we have 220v ac here

mattthegamer463 (author)  JohnF71 month ago
Sorry I misunderstood. I thought you were asking how you could do this without a transformer at all. The transformer outputs 18V but takes in 110V AC. Plugging a 110V transformer into 220V will cause the output to be 2x higher, but you will be able to buy a 220V to 18V transformer there in the Philippines. The input and output are referred to as "Primary" and "Secondary" coils, which will be rated for 220V and 18V respectively.
JohnF71 month ago

man, thanks for this tutorial. but i live in a country which i get a 220v ac., what can i do if dnt wanna use transformer? thank you. im a newbie in electrnics.

mattthegamer463 (author)  JohnF71 month ago
You have to use a transformer. There isn't any practical way to make 9V DC from 220V AC.
rocking0181 month ago

is this an isolated power supply or is that a whole different game?

mattthegamer463 (author)  rocking0181 month ago
One of these per output could be used to make a isolated supply. Cost could probably be about $20 + extra $6 per output.

http://www.digikey.ca/product-detail/en/PDS1-S12-S9-S/102-3012-5-ND/4006980
mattthegamer463 (author)  rocking0181 month ago
Totally different game. Isolated outputs require each output to have an isolating DC/DC converter (expensive) or a specialized transformer with many isolated output secondary windings (very expensive). With properly grounded cables, using an unisolated power supply shouldn't be a problem. Most retail units are not fully isolated either.
Davidv33 months ago

is it a problem if you live in a country where you get 230 volt ac out of the power outlet?

mattthegamer463 (author)  Davidv33 months ago
No, you just need a transformer which has a primary rated for 230V AC and a secondary rated for 9V AC. Some transformers can be wired specifically for 115V or 230V, but probably most cannot.

Wouldn't a 230 – 12 VAC work too? And would the LM7809's be able to operate at all if the secondary was 9 volts? – The datasheet specifies a minimum input voltage of 11.5 volts.

It would, just that the more excess voltage you have at the unregulated DC stage, the more heat the regulator is going to generate and the less current you will have available at the output. Because the transformer current rating is selected to be higher than the current that is actually going to be used, it will be higher than 9V. The rectified and smoothed output voltage of a 9V secondary, with no load, t is probably 14-15V. Using a higher transformer rating would just produce more voltage the regulator will have to waste.

The dropout voltage in the datasheet is 2V @ 1A, but 1A is the maximum current for the part. It would probably take 8 typical pedals on one output to use that much current. The dropout voltage is lower at smaller current levels. A part like the TI LM2940CT-9.0 is an improved linear regulator design that only has a dropout of 0.5V @ 1A. It is pin compatible so it can replace the generic 7809 directly.

Thanks for the informative answer; exactly what I needed to know. :)

Jj.Diamante242 months ago

what will i do so that i'll have eight 9VDC outputs?

mattthegamer463 (author)  Jj.Diamante242 months ago
Multiply the regulators and output capacitors to get as many outputs as you want. For 8 outputs I would recommend at least 1A @ 9V transformer output current.

Matt,

I am a lil confused about your circuit diagram vs. your list of components. The diagram shows (4) 100 uF caps and (2) 10 mF caps. Your list is saying use (3) 10 uF and (2) 10 mF or (2) 100 uF for less overkill. I like your design and I wanted to build one, but I dunno if I should have 6 caps or just 5 caps?

You'll need a cap for each regulator output, so I would recommend you use one 10uF and two 100uF before the regulators, and a 100uF after each regulator, from the output to ground. To prevent any oscillations I would also add a 100nF in parallel with each of those output capacitors. This is good practice that I was not aware of 4 years ago when I did this Instructable.
LennertO2 months ago

What is the minimum current that the secondary side must be able to deliver?

mattthegamer463 (author)  LennertO2 months ago
The one I used only delivers 300mA. You could get away with less if you are only powering 3-4 pedals, and no vacuum tube pedals.

Hi Matt,

Very cool. Good work!

I just had to replace CO alarms. The old ones have 9V AC transformers. I recently bought a great pedal without a power supply that can take 18V DC. Can I simply run each of the two transformers from the CO alarms into diodes in a bridge rectifier configuration and connect the + and - from the diodes before sending them to a voltage regulator (I understand I lose some voltage). There isn't a good way to combine the transformer voltage before making it DC, is there?

Thanks!

mattthegamer463 (author)  stephen.silbert2 months ago
You should be able to do something like this

http://i68.photobucket.com/albums/i5/Morocotuco/XFORMERS-IN-SERIES.jpg

Putting the primaries in parallel and the secondaries in series will give you twice the output voltage. Be careful and test it out first.

THANK YOU!!!

liamd7922 months ago

Just a question, as i'm thinking of making this for my friend for his band, how does it connect to the pedal to power it?

mattthegamer463 (author)  liamd7922 months ago
Female to Female 2.1mm barrel jack cable. You can make your own or buy them. Like these.
stefanrichter8 months ago

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)  stefanrichter8 months 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.

Hey Matt, thought this might be useful info for others: easy to find, 8 isolated tap, transformer for $25 plus shipping:

https://taweber.powweb.com/store/magnetic.htm scroll down to the bottom for item

WPDLXFMR-1 or

WPDLXFMR-2 depending on your input voltage.

nursetom616 months ago

If only making the outputs 9v, what is the maximum number of outputs you can make? I have a lot of pedals and want to make a pedalboard. I am thinking, I need to build at least 2 supply boxes.

mattthegamer463 (author)  nursetom616 months ago
The circuit is fully scalable, the transformer power rating just has to be appropriately scaled as well.

I am still not sure about the transformer. If I have 10 pedals for example and they are all 9 volt. Does this mean I need a 90 volt transformer? I probably have closer to 15 pedals and want to make one circuit a SAG. I am thinking about some kind of Pot. Also do I need to match the Amperage to each pedal? Probably won't be able to do this for a few months but would like to start gathering parts. Also since you have a plastic housing. Can I use a metal housing?

mattthegamer463 (author)  nursetom616 months ago

That's not how it works. The transformer just needs enough voltage overhead for the linear regulators to work properly. The pedals are powered in parallel. Bad stuff would happen if you wired them in series. Also I don't know what a SAG is.

You don't need to match the current to the pedals, just the voltage. The pedals will draw what they need. Metal housings are fine, just make sure you hook the green earth ground wire directly to the chassis for safety.

mattthegamer463 (author)  nursetom616 months ago

That's not how it works. The transformer just needs enough voltage overhead for the linear regulators to work properly. The pedals are powered in parallel. Bad stuff would happen if you wired them in series. Also I don't know what a SAG is.

You don't need to match the current to the pedals, just the voltage. The pedals will draw what they need. Metal housings are fine, just make sure you hook the green earth ground wire directly to the chassis for safety.

mattthegamer463 (author) 6 months ago
You're going to need a bridge rectifier, one that can handle 2A of current. Virtually any bridge rectifier with four leads like shown in the pictures of the parts will work.
VoxAC156 months ago

Matt, thanks for these plans. I am somewhat of a neophyte when it come to electronics, but have always wanted try my hand at it, this looks like a fun project. One question though. I am having a real hard time finding an 18 V 300 ma Transformer. I see in a previous post that you mentioned using a 12V AC @ 1.2A transformer would be ok. I assume no other changes are needed are far as the ratings on the other components to accommodate the above transformer. Alternatively I was wondering if I could just open up a 18V 300ma AC Adapter rating you mentioned, since it has a transformer in it? Thanks man.

mattthegamer463 (author)  VoxAC156 months ago
Yes, you're on the right track there

Also, I see from your images that you have a bridge rectifier, but didn't see it in your list of project parts. Is that needed and if so, any specific specs I need to look for on that? Thanks again man

shoelesscraig7 months ago

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)  shoelesscraig7 months 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.
spunko9 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)  spunko9 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!
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