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.

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:


Step 2: Parts and Tools


- 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


- 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.


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!

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!


<p>Amperage output of the transformer doesn't matter too much does it? I have a few 12V 4A transformers sitting around I'd like to use and I didn't notice a maximum amperage on the 78XX spec sheet. Each VR would receive 1.3A in this instance with a regulated output of 0.5A to 1A, each power socket would receive 250mA to 500mA if I'm not mistaken. Some of my Boss pedals specifically require no more than 200mA. Connecting an additional one or two power sockets to each VR could mitigate any issue there but only so long as an actual pedal is connected to each socket and drawing power, thus divvying up the current equally. Any thoughts on this?</p>
Circuits only draw as much current as they want. Difficulty is, ohm's law dictates that the higher the voltage across a fixed load, the more current it will consume. 2x the voltage = 2x the current = 4x the power = poof of smoke.<br><br>If your boss pedals want 200mA, they'll only take as much as they want.<br><br>Your 4A transformers can deliver 12V and 4A, they might run a little higher voltage with a light load on them, but they will work. The max amperage of 78XXs is pegged to the case type. The TO-3 package can handle up to 1.5A with a heatsink, I think, however, the true limit is linked to the difference between voltage in and voltage out, the amount of current being drawn, and the thermal coefficient of the junction to case, case to heatsink, and heatsink to air.<br><br>In short, you won't draw more current than you need, as long as your voltage is regulated and correct. It doesn't matter if the supply can deliver 100mA or 100A.
<p>Hey Matt ! </p><p>Good project ! and excellent explanations . You stressed the importance of the voltage rating of the capacitors , another thing that a novice might miss , would be the polarity of a capacitor , hook it up backwards , and it will smoke ! A little humor here :</p><p>All electrical devices operate on the captive smoke inside it . When the smoke gets out ,the device quits working !!</p><p> One analogy that may help folks to understand what you said about things just drawing the current that they need , would be a car 12V ( actually about 13.8V , but close enough ) electrical system . The battery can give the starter motor hundreds of amps , but the radio , headlights etc , only draw the current they need to operate . As far as transformers go , It pretty much has to do with the turns ratio ,( the primary voltage vs secondary voltage ) , and is normally rated as an RMS value . When you rectify the AC voltage and feed a filter capacitor , the capacitor ( under no load or very light load ) will charge up to the &quot; peak &quot; voltage value , around 1.4 times the RMS voltage , less the voltage drop across the rectifiers . This kind of explains the need for using a regulator circuit to keep the voltage constant . There are all sorts of modifications that could be done to this circuit , the sky is the limit ! One thing that could be done would be to use a separate regulator and capacitor for each output ( they are cheap , 78xx regulators can be bought for about $1 US each or less ) This could help if you find you are getting &quot; crosstalk &quot; noise between pedals . A beefier transformer certainly wouldn't hurt anything either .</p><p>Cheers , take care , and have a good day !!....73</p>
<p>Thanks. I agree there's room to grow with this design.</p>
<p>Great Instructable! Thanks. Do you see any reason why I couldn't take a computer power supply and regulate the DC voltage down to 9VDC? I have an old laptop power supply that is 20VDC. What are your thoughts?</p>
No that should work. Some laptop supplies may not be a very clean power source, though. Might end up with some audible hum.
Ok. That was my only worry. Maybe it's not worth it then. Where did you get your transformer? Seems like they are $30-$40 in mouser. Or a part number would be awesome. Thanks for the help.
<p>You'd be best off finding a transformer somewhere and using that. The old heavy wall-warts have a transformer in them, which you could use. Something from 9 to 15V output would work with a 7809 linear regulator. The higher the input voltage the more wasted energy and the more heat the 7809 will generate, but that's okay if you have a heatsink. The 78XX series is good up to 35V if I recall correctly, so the only issue is heat dissipation. They have integrated thermal protection that shuts them down at 75C so they won't normally damage themselves too quickly. Also they're pretty cheap so buy a couple extras and if you blow up a couple while figuring out how much cooling you need its not a big deal.</p>
<p>is this an isolated power supply or is that a whole different game?</p>
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.
<p>Hi Matt, I was wondering what made you choose the DC/DC converter that you did as I'd be interested to find the 6V and 12V converters as well? Also, as the min input voltage on the converters is 10.8, does that mean the circuit needs different regulators to feed the higher input requirement of the converters? Or, do the converters replace the regulators?</p><p>Thanks for the help!</p>
<p>The DC/DC converters replace the regulators, they basically just regulate the voltage but in a more efficient way. Some also feature isolated outputs. The unregulated DC from the rectifier and capacitors just needs to be within the module's input range.</p><p>If you're interested in the isolated power aspects, you can also use the converters and just hook them to an off the shelf DC power supply. One like the one below will give isolated 9V from 5V DC from a wall adapter.</p><p><a href="http://www.digikey.ca/product-detail/en/PDS1-S5-S9-D/102-3024-5-ND/4006992" rel="nofollow">http://www.digikey.ca/product-detail/en/PDS1-S5-S9...</a></p>
<p>Awesome project!!! and very clear directions<br></p><p>I am trying <br>to make a mod based on your design. In sum, the project is an attempt <br>to replace a mess of wall warts(photo1). It REQUIRES isolation, as I have many <br>different synths/effects that all run through loopers(photo2/3), so any extra <br>noise compounds really quick. Many use different volts/amps, so it is <br>unlike a standard guitar pedal board that uses uniform-ish pedals. The <br>outputs needed are:</p><p>(4) 4.5V, 1A, pin positive (kaossilators)<br>(2) 9V, 1.7A, pin positive(kaoss pro, korg wave mini)<br>(1) 9V, 1A, pin negative (boss rc-50)<br>(1) 9V, 300ma, pin positive (roland midi splitter)<br></p><p>(1) 12V, 400ma, pin negative (TC helicon)<br></p><p>(1) 12V, 700ma, pin positive <br></p><p>From my limited understanding, I feel it is easiest to use a computer CPU (or similar) and run a DC/DC converter (<a href="http://www.digikey.ca/product-detail/en/PDS1-S5-S9-D/102-3024-5-ND/4006992" rel="nofollow">PDS1-S5-S9-D</a><br> or similar) off the 12v or 5v rails, using one converter for each <br>desired output. This would be done in parallel (correct?). I would <br>prefer to run ALL off the 12 volt rail, because at some point I would <br>like to power this off a portable car battery(and make the whole unit <br>portable). If possible, I would also like to fit all the components onto the board <br>that the synths are mounted to (photo 4/5). I plan to leave the CPU<br> on the ground to reduce EMI noise. Ideally, one cable will connect from CPU to the board, which will have all the circuitry to step down power, reducing the number of plugs I have to undo/redo every time I take this setup out for gigs</p><p>I am only unsure if this <br>will yield the proper results, be safe for my components, and not tax <br>the power supply(or find one that is well equipped to run all this). Also fuses will be required. Any insight you can <br>provide here? </p><p>Again, <strong>the focus is</strong>: power isolation, EMI reduction and <br>portability/form factor. Cost and time are not factors, unless we are <br>talking on infinite scales :)</p>
<p>also, how does one achieve the isolation effect of these converters for outputs that need 12 volts (and thus don't need to be stepped down)?</p><p>Bonus: I also have a behringer mixer that has a (2x 18.5v, 350ma) wall wort I would like to replace. But that is a less straight forward job of soldering the connector. </p>
<p>Well that is quite a complex set of requirements. You may have a hard time finding DC/DC converters which give you enough current to run some of these units. Many of the DC/DC converters that are low cost only output 50-100mA.</p><p>The easiest way to do this would be to build a bunch of isolated power supply circuits using dual-secondary transformers and linear regulators, then you can select each regulator based on the device it has to supply, and you won't have any current issues. The transformers you would need could be found pretty cheaply on eBay, and you could buy a bunch of the same ones and just multiply the circuit as many times as needed. Here is an example of the circuit giving two isolated 9V outputs.</p><p><a href="http://s8.postimg.org/d6b5nro0l/shuper_fuente_scheme_2.png">http://s8.postimg.org/d6b5nro0l/shuper_fuente_sche...</a></p><p>Multiply as needed, power them all from the same 115V supply. For portability, build in or connect one of those 12V to 115V car cigarette lighter inverters, easy to hook to a car battery with no hassle.</p><p>This transformer would give you two 4.5V 1A outputs for kaossilators <a href="http://www.digikey.ca/product-detail/en/VPP10-1000/237-1053-ND/242497">http://www.digikey.ca/product-detail/en/VPP10-1000...</a></p><p>This would give you two 12V 100mA outputs for 12V pedals, you could use the same one for the 9V pedals as well <a href="http://www.digikey.ca/product-detail/en/VPP24-100/237-1064-ND/242508">http://www.digikey.ca/product-detail/en/VPP24-100/...</a></p><p>This would give you two 18V 500mA to run your 18V mixer <a href="http://www.digikey.ca/product-detail/en/VPP36-560/237-1073-ND/242517">http://www.digikey.ca/product-detail/en/VPP36-560/...</a></p><p>So with each transformer you use a bridge rectifier for each secondary winding, and the appropriate regulator to supply each pedal you want to run. The rest is just wiring. You can fuse each output to make sure your pedals are protected if you'd like.</p><p>Obviously this is a pretty involved solution, but I don't see any other elegant way of doing it, aside from just taking those wall warts and zip tying them to a power bar, and putting that in a box with all the cables coming out a single hole. The plan I've proposed is electrically quite similar to whats going on inside all of those wall warts anyway, just extracted and condensed into a single giant power supply circuit.</p>
One of these per output could be used to make a isolated supply. Cost could probably be about $20 + extra $6 per output.<br><br>http://www.digikey.ca/product-detail/en/PDS1-S12-S9-S/102-3012-5-ND/4006980
<p>Great build Matt, thanks.</p><p>On your photobucket feed, there is an effects pedal with a tube installed on it. What is that, and could you share how it was made?</p>
Here's the forum about it. Hopefully these tubes can still be found. They don't glow, by the way.<br><br>http://www.diystompboxes.com/smfforum/index.php?topic=70533.0<br><br>As I was writing this I realized you said &quot;tube&quot; singular, not plural. If you're referring to the single 12AX7 tube on a box, I don't remember what that pedal was. It never worked properly and I still have it sitting here, gutted, waiting for some kind of circuit. There are a lot of 12V 12AX7 based distortions/crunchers on the net though so you won't have a hard time finding one if you're looking for a tube-based pedal. They don't sound as great as you'd imagine. They do look neat though. Since then I've stuck to tubes for HiFi only (and a modern fender tube amp which I don't dink around inside)
<p>This is very cool and I thank you much for it's creation.</p>
Thanks. Great Instructable. I took the same schematic and same idea, without the project box, and mounted it to the bottom of my pedal board I made! Check it out...<br><br>All six DC cables are 9v, and I put two through each hole in the board, for maximum movability.
Nice job, looks great
<p>Hi Matt, I am a little confused on the parts. What are those two large cylinders on top of the whole power supply box. (Blue and Red on computer graphic)</p>
<p>Actually only blue on the computer graphic. still same question</p>
Hi there, sorry for the delayed response, the Instructables email system seems to have broken until just today.<br><br>Those are large capacitors sticking out of the case. They are like that only for cosmetic reasons, they are much larger than the circuit requires. Feel free to use a lower value like 1000uF, they will be much smaller.
hi sir mat, i made power supply based on your schematic. i used a 18 0 18 @1amper transformer, but when i tested it, the output from both 3 regulators was uniformed @ 19 - 20vac. where did i go wrong.? how should i fix it sir.? tnx.
You should have no AC voltage at the output of the regulators, only DC voltage. Check the pinout of your regulators to make sure they are wired correctly, also make sure your bridge rectifier/rectifier diodes are correct because you should not have that high an AC voltage if you have the rectifier and capacitors in place.
<p>an easy way to get the power for pedals is to buy a cb regulated power supply then turn the regulator voltage down to 9 volts..might be a variable pot or a resistor change..simple ...im getting a bit of a chuckle at how many guys are tring to complicate the issue....its a very simple problem to get around</p>
<p>Hey Matt, I've followed the schematics, and wired everything up accordingly. Thanks a lot for the comprehensive instructions !</p><p>I'm facing a small problem though: when I check the voltage from each port, they all produce -9V DC. However, once I use a port to power my pedal, something seems to eat all the current up. My pedals are regular, 9V, and draw 14-19mA. What do you think could cause this?</p><p>Interestingly, when I try plugging in a cheaper pedal, it works just fine.</p>
<p>sir i have a transformer 220v to 12v outputs my problem is the transformer is have 3 pins 12v 0v 12v what should i use the 12v and 0v? </p>
There is a way to use a center-tapped transformer without getting too high a voltage if you just ignore the center tap. This is done with a full wave rectifier as shown here:<br><br>http://savedonthe.net/image/1761/full_wave.png<br><br>Just replace the bridge rectifier in my circuit with two diodes to make a full wave rectifier as shown.
<p>hi sir in your diagram where did you put the the two 1000uf volts capacitor and 3 10 uf 63v because in the diagram only 100uf numbers no voltage included sorry sir im a newbie -_-</p>
<p>because i count all the capacitors in the diagram there are 6 and the one i saw in your pictures is only 5 can you plase create a diagram that shown all the name of capacitors thank you sir for all the help</p>
<p>The value and quantity of the capacitors really isn't that important, what is important is where they are located and that the voltage rating for them is higher than the maximum voltage they will be subjected to. Subjecting a capacitor to a voltage higher than its rating can and will cause it to burst or explode. Just google this to see why you don't want this to happen.</p><p>Capacitors after the rectifying diodes (before the regulators) and after the regulators (a requirement stipulated in the 78xx regulator datasheet) is all you need. If you have major noise problems being caused by the power supply after it's built, I would suggest to add some more capacitors in parallel with the existing ones to help smooth out the voltage. </p><p>The 10000uF capacitors are oversized. They are functional but their huge value is partly cosmetic. Feel free to substitute a single 1000uF if you'd like, there shouldn't be any issue.</p>
<p>More info if you want to learn about it</p><p>http://www.daenotes.com/electronics/devices-circuits/center-tapped-full-wave-rectifier</p>
<p>sir i have a transformer 220v to 12v outputs my problem is the transformer is have 3 pins 12v 0v 12v what should i use the 12v and 0v? </p>
<p>Dude. I want to have 9v 8 outputs. What should I do? I already get it in replacing the other 12v and 5v regulators with 9v one. How to add another 9v in the circuit? Thanks</p>
Just add some more regulators and capacitors. If you add one more (4 total) you can put two pedals on each and have your 8 outputs.
<p>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</p>
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 &quot;Primary&quot; and &quot;Secondary&quot; coils, which will be rated for 220V and 18V respectively.
<p>Hi.. So can I replace your transformer with 220v AC with 18v AC secondary rating?</p>
<p>Yep, that's the way.</p>
<p>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. </p>
You have to use a transformer. There isn't any practical way to make 9V DC from 220V AC.
<p>Huh? Of course you can do it with a Zener diodes. E.g., please read this: http://www.designercircuits.com/DesignNote1a.pdf The other question is that it is not always that safe and if you have crappy jumping power, then all your pedalboard might puff in smokes, once you use Zeners at the limit. Transformers are just nicer and safer.</p>
<p>I would never suggest someone not use a transformer for this kind of thing, especially for 220V AC. Not just for safety reasons, but for practical reasons too. If you do the math on a zener regulator circuit, the voltage drop resistor would need to dispose of more than 10W of extra power to get 50mA on the output, enough for only one or two pedals. Also, he says he is new to electronics, which frankly means he really shouldn't be messing around with 220V AC without the knowledge of how to be safe. Transformer or no, 220V AC is dangerous.</p>
So with that transformer you can only use 300ma worth of pedals correct?
Pretty much. Won't be hazardous to go over that a little bit though.
Or do you get more since you're dropping to 9v?

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