Guitar Pedal Power Supply

First of all, thank you for the forum, I’m new to it and I’m starting both in Kicad and in electronics. I apologize for my level of English and I hope I can express myself correctly.
I want to build myself a power supply for my guitar pedals. The input current will be 220V AC that I will transform into DC, I still have to decide if only with a 9V output or with several independent outputs (9V, 12V and 15V).
I want to try the following circuit:

When I click on the simulator it gives me the following error:

Note: No compatibility mode selected!
warning, can’t find model ‘lm7805’ from line
u1 out_rectificed 0 net-c3-pad1 lm7805
Circuit: KiCad schematic
Error on line 10 or its substitute:
u1 out_rectificed 0 net-c3-pad1 lm7805
Unable to find definition of model lm7805
Background thread stopped with timeout = 0
Error: circuit not parsed.

I don’t know what I’m doing wrong or what I should correct. I am using the Kicad 6.0 version on Ubuntu 18.04. I would appreciate any help you can give me as I am stuck here.

Thank you very much, regards!

If you get new into electronics don’t mess with 220V AC. never. Buy a standard power supply with your required voltages and integrate them in your device. they are available in all sizes and forms and you don’t risk killing yourself.


If you put 230V AC into a rectifier bridge you will get around 325V DC peak, the regulator you chose (and pretty much any other linear regulator) will blow up at that input voltage. Just like Tojan said, use a standard power brick and don’t bother trying to make your own. Standard 5V phone charger will probably work well and there’s a good chance you have one laying around.


Thanks Tojan for the advice.
I have already built some guitar pedals and I have modified a pc source to build a power supply with variable voltage and intensity, always with the help of the internet.
My intention is to learn and try the Kicad simulation before burning down the house, the previous circuit still needs to put a transformer that will lower me from 220V to 18V (it depends on the final outputs) and some more details that I will add when go forward.
What I want to do with Kicad is to progress little by little until I get the project, but I need to see how each component in my scheme works. The problem is that with the error that I mentioned above, I get blocked and I can’t continue.
I’m not in a hurry to build it but curious to do it myself. Thank you very much again Tojan


It seems there’s no spice model for the LM7805 regulator. I’m not very familiar with spice in kicad, but I believe that you can add it in the “symbol properties” window.

Learn to consult data sheets. Absolute max input voltage for the regulator is around 35 to 40 volts. The reality is you don’t want to go anywhere near that value in actual practice. I’m no expert but I think you would need a transformer in the circuit to step the voltage down. What you should learn from this is that it really isn’t a DIY project when you can get a commercially available much cheaper and more reliable product than you can build, or should, build. :wink:

You got my attention… Been playing Guitar for 65 yrs! Mostly Jazz for past 40 yrs.

I make (or, should say, ‘fool around’ with making audio gizmos for fun).

Power: Stay away from doing anything beyond using a standard Power Supply (example low cost example here)

You can Bring the power to the PCB via the connector and split the Power to three Regulators such as LM78xx where xx are the desired voltages you want (look up the LM78xx)

Simulation: You can use Kicad’s NGspice but, learning curve is much steeper than LTspice and LTspice can do it all…
Example screenshot shows a very simple Audio Amp with Wave file simulation (usually I bring in a Wave of the Guitar sounds I want to tweak…)

EDIT: exchanged video for one with Guitar example

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Apart from putting rectified 230Vac into a poor LM7805, grounding both sides of a bride rectifier does not work.

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Thank you all for the tips and advice.
I upload a schematic of what I really want to learn how to do and simulate in Kicad:

I have not calculated costs yet, it is something more to learn than to save money, if in the end it really shoots me it comes out for a very high price I will leave it alone in learning but something that I take with me. There are some of the materials for the possible circuit that I have at home from other devices or projects.

I have tried to set up the scheme of this post in Kicad, but my knowledge of the program is still very limited and it gave me a lot of errors, which is why I am trying little by little how it works and how to simulate different circuits that can be useful for me. I have to learn to calculate capacitors, the properties of the transformer,… so that the simulator doesn’t fail me.

-Dawid_Cislo, I will try to find out how the “Symbols Properties” window works to try to solve the error that the LM7805 gives me

-hermit, you’re right, sorry, the fault is not having put the schematic closer to reality. No more than 24V and 1A of intensity will come out of the transformer, so that the LM7805 can withstand it. In case they had to be higher values, I would change it for an LM337 for example or the one that corresponds to it.

-BlackCoffee, the problem with the LM78xx regulator is that it gives me an error when I put it in the schematic and try to simulate it, I guess there’s something I’m not configuring right.

-paulvdh, sorry, I didn’t realize it was a duplicate, I delete it.

Thank you very much to all!

A simple power supply is not very expensive, if you don’t have much experience with electronics, I suggest you stay away from direct mains voltages and start with a wall wart that has a low voltage DC output. If you need (approx) 5V, then a standard USB charger probably works, for an LM7809 as in your 2nd schematic, something around 12V is more suitable.

Also, for such one-off projects it’s often easier to start with some scavenged transformer and just screw it somewhere in the housing. This also has the advantage that high voltages are kept far away from the PCB, and from your fingers during fault finding. Transformers are bulky and heavy too and that makes them annoying to have on a PCB too. For hobby projects I usually isolate all mains related voltages (power entry, switch fuse, transformer) with an extra layer of heat shrink tube, so I only have to think about 230Vac once during building.

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Hi, You get my attention too. Used to repair guitar equipment for many years as a business.

First of all LM7805 is 5V out, not 9V! If you want to stick with this IC series use LM7809 instead :slight_smile:

Second thing - if you decide to for for multiple outputs - bare in mind that most “classic” pedals are 9V tip negative (Boss, newer Ibanez pedals, etc). However lots of fancy pedals with voltage different than 9V DC have tip positive (not all!). That may cause shorting your PSU outputs to GND. I’d suggest you to have transformer with multiple outputs and have secondary parts for different voltage rails completely separate. that will also help you for humming due to ground loops, etc.

Very short summary:

It all depends how much current you need for 9V DC, but if it is just some 100-200mA (like a couple opamps), then a PCB mounted transformer might make sense.
Make sure to keep 10mm distance everywhere at a minimum between the mains side and the secondary side. (This is a rule of thumb for amateurs, if you have special conditions or commercial production you have to follow a long list of rules and standards.)
Transformer secondary about 9V AC.
C1 about 1000µ 25V. C2 100n 63V or at least 25V.
C3 100n at least 16V C4 47µ 16V.
7809 needs some kind of heat sink unless the current is very low, like under 100mA.

There isn’t that urgend of a need to simulate the thing; a 7809 is a fairly standard and forgiving thing and is likely to work as expected as long as you have enough difference between input and output voltage (min 3V at worst case).

Notice: This is purely from my own experience - call it “speculation” if you will. I take no responsibility for what anyone else does, whether they follow my ideas or not!

Don’t mess around with mains voltages until you know what your doing-just dont!

Anyway, some background info, for mains the voltages as ‘advertised’ values are RMS values (Root Mean Square). To get the peak voltage you must multiply the nominal voltage in your country (220Vac) by 1.414 (actually Sqrt of 2) = 311V.
However there’s a gotcha for young players here — notice I said ‘Peak’voltage and NOT’ Peak to PEAK’ so the actual voltage as seen by componentsp on the mains side would by double so that would be 622V Pk to Pk. Mains voltages are alternating equally around the zero point.

As others have stated it is FAR easier and safer just to by a commercial linear voltage regulator to suit your needs. Also, remember that cheap and nasty voltages regulators usually often have noise superimposed on the ‘regulated’ output voltagev because they are a Switched Mode Power Supply Units.

Lastly, if you insist on building your own circuit you WILL need a transformer - you’ll blow the living crap out of the those poor diodes!! And ideally I would add some additional caps of various sizes (you can research why and if actually needed)


Firstly welcome and I would wholeheartedly agree with all the opinions given here regarding actually building this it’s much easier and safer to ‘Buy’ than ‘DIY’ but now maybe try your question again in another category other than projects, not sure I can be much help as to which one to use but I understand that you want to simulate this for your own personal growth and understanding.
I’m kinda new here too so dont know the best place for advice on ‘Kicad Simulation’ but maybe the ‘Community’ category would be the place to start. Not much help but good luck with the project :grinning:

No please don’t. Questions about learning to design circuits are already out of scope for this forum. It’s partly tolerated in the Projects category as some kind hearted users might contribute but if the discussion strays it’s liable to be closed.

I also don’t understand the mania towards stimulating even simple circuits. The problem with simulation is if you need it then your understanding is already not basic. Reading text books, datasheets and design notes are more likely to useful.


OK so simulation in kicad does not work by just putting components in. The library models don’t usually come with simulation components associated with them.

So you need to start by finding the spice models for your components online then going to symbol properties and clicking the spice model button at the bottom, then under Model tab you need to select the file with your spice model and the model name from Model drop down.

But your not done yet you still need to read the mdoel and deduce the node sequence because pin numbers are frequently different form kicads pin numbers.

I would follow advice of BlackCoffee and use LTspice first. Then when your comfortable using LTspice you can start into looking into using the simulator in kicad. But then how to verufy your stuff is another can of worms.

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You may have a look at Simulation examples for KiCad/Eeschema/ngspice - #4 by holger where you will find a simulation project using the LM317.


Re: NGspice: it’s a good Simulator but requires too much fussing. Once getting an inventory of Parts with Spice models, moving forward is still a ‘can of worms’ IMO but, I’ve had good success with it.

Re: LTspice: I favor LTspice and simply won’t use NGspice anymore…

Re: LM7805 in Kicad’s NGspice: Sure, you can:
• build a Spice model-file for LM7805
• include the Model parameters in the Schematic if desired (versus calling out a File or loading the values in the panel)
• use quickly implemented values (without the characteristic you might want) by entering the values into (either the Spice Model Editor or Symbol Prop Panel) you choose as the value will appear in both… screenshot below

Current not depends on transformator but on load connected to 7805 output.

It is not so easy. What is limiting the current you can get from your supply is the power dissipated in 7805 or LM337. The temperature of chip inside IC is limited and you have to learn to calculate that temperature based on IC and radiator parameters.

Long time ago, being in primary school, starting to be interesting in electronic I was not able to get workshop equipment I needed so I started from doing them myself. One of first was the power supply. I used some 100W trafo from damaged lamp radio receiver. I rewound its secondary winding to get output voltages (many tappings) in the sequence: 6+6+6+6+6+1+1+1+1+1. From it, using banana plugs I can get any voltage from 1V til 35V (1V step). Then through diode bridge and capacitor it goes to stabilizer. I can get any output voltage from 0V to 40V and with regulated current limit. It is not aesthetic. The case is made of plywood but it still works. Which modern device is expected to operate in 50 years.
The key is to select right voltage from trafo depending on what voltage and current you need to get at output. If the input voltage is too high than heat dissipated in main regulating transistor can kill it (my supply has no temperature protection).
If you dissipate 1W in 7805 without radiator it will be working but it will be so hot that you will be not able to keep it in your hand.

I am a power supply designer. I have been doing that since 1980. But if I need power for a home project, I will almost always use some leftover commercial unit such as the power adapter from an obsolete laptop computer. Power supplies are cheap enough and difficult enough…it does not pay to build your own for anything less than thousands of units (unless you have a high budget for some bona fide reason.). There is also substantial safety risk in an AC-DC power supply.

Just in the last couple of days: I had been using an old cell phone in the garage as only a clock. I think it is a “3G” phone. I think that the wireless carriers “pulled the plug” on 3G so now this old phone has been effectively “bricked” and no longer can tell me the time. The power adapter (charger) for it is rated 5V 0.7 Amps. That is just fine for some small projects. I have at least a couple of those power adapters now, in addition to a fair variety of others. I do not throw these things away. Also…think of power adapters from old “cordless” land line phones… Hang onto these sort of things and you might not need to worry about coming up with AC input power supplies for small projects. DC/DC conversion or linear regulators are much more user friendly.

And…instead of worrying about 7805s and 7809s, etc. Get yourself a small stash of LM317s. Those work really nicely and can be adjusted to anywhere from (I think 1.25V) up to maybe 30V or so. You just need resistors…

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