Guitar Pedal Power Supply

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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That is right! Also even:
Inverted 7805
will not give you -5V. :slight_smile:

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My favorite upside-down number is 5318008 (but it needs to be on a 7-segment display)


And I’d give you a “like” too, except my neck now hurts!

I did not know whether he wanted it flipped upside down or rotated upside down. But with the help of a hint I have figured it out now… It is advanced mathematics… :crazy_face:

Seriously advanced. :yum:

Recently I have bought 2 laptop power supplies (90W, 19.5V, 4.62A, for DELL laptop, new, but not original). The price was only 22PLN ($5.15) per one. They are cheaper than others because they are sold without power cable. I (as probably many others) have these cables from old, broken power supplies.

Laptop PSUs are SMPS. This is definitely not advised for guitar pedals. Don’t go that way! Linear only!

Indeed, the sources for pedals must be linear to avoid noise.
From what I was seeing, a power supply for pedals with different outputs like the one I need/want (8x9V, 1x12V and 1x18V) cost between €150 and €200, hence my interest to see if it was possible to build it myself and see if it was economically profitable.
I know it’s not an easy task, but I don’t mind reading, researching and learning new things.
I appreciate all the answers and I will follow your advice, I will continue researching the different components that can help me and I hope to progress little by little with the project.
If the moderators don’t mind, I’ll upload the possible advances to the post and, above all, I’ll keep reading and seeing other projects to learn and get ideas.

The good quality branded guitar pedals PSUs have custom transformer with multiple outputs, so then it’s possible to have separated outputs. This is not easy to replicate in a DIY project. Probably 2-4 outputs max from one transformer is the best what you can find.

Generally I agree, but…
Nowadays there is so much RF noise all around that SMPS power supply standing 1m away will probably not be a problem with propagating waves through air so only propagation through cables left. May be making a good filter (with big common mode choke among others) will be simpler than doing the poser supply.
But only may be.

Generally I agree with you Piotr, but:

  • if the PSU is on a pedalboard it may be 10-20cm away from the pedals and signal cable (or even less)
  • it’s not about about the distance, but the “cleanness” of the output DC (difficult to filter out)
  • (the most important thing!) give a linear and SMPS to any (semi)professional guitarist to try and ask them which one they prefer