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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mau12.162 days ago

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

mattthegamer463 (author)  mau12.16yesterday
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.
JohnF73 months 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)  JohnF73 months 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.

Hi.. So can I replace your transformer with 220v AC with 18v AC secondary rating?

mattthegamer463 (author)  mau12.162 days ago

Yep, that's the way.

JohnF73 months 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)  JohnF73 months ago
You have to use a transformer. There isn't any practical way to make 9V DC from 220V AC.

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.

mattthegamer463 (author)  bo.maryniuk19 days ago

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.

So with that transformer you can only use 300ma worth of pedals correct?
mattthegamer463 (author)  evan.stoddard21 days ago
Pretty much. Won't be hazardous to go over that a little bit though.
Gotcha.
Or do you get more since you're dropping to 9v?
Davidv35 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)  Davidv35 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.

what about SMPS?

mattthegamer463 (author)  Okoraokora11 month ago

An SMPS would work but the concern is that the SMPS high frequencies will cause noise and high frequency sounds.

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. :)

rocking0184 months ago

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

mattthegamer463 (author)  rocking0184 months 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)  rocking0184 months 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.
Jj.Diamante244 months ago

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

mattthegamer463 (author)  Jj.Diamante244 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.
LennertO4 months ago

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

mattthegamer463 (author)  LennertO4 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.silbert5 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!!!

liamd7925 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)  liamd7925 months ago
Female to Female 2.1mm barrel jack cable. You can make your own or buy them. Like these.
stefanrichter10 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)  stefanrichter10 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.

nursetom619 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)  nursetom619 months ago
The circuit is fully scalable, the transformer power rating just has to be appropriately scaled as well.
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