That is right! Also even:
will not give you -5V. 
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My favorite upside-down number is 5318008 (but it needs to be on a 7-segment display)
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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… 
Seriously advanced. 
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.
Regards!
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
I have never had any to do with serious acoustic electronic.
In theory if current SMPSs work at 200kHz or more they should have no influence at acoustic band.
Most of DCDCs try to have as high as possible efficiency at low loads and the effect is they start to work not continuously and it certainly jumps into low frequency band with all effects possible.
Being not sure of it I suppose it is the main reason of bad opinion of SMPS used in acoustic circuits.
As step-down I am using LM5017. It allows to step down from 100V to 3V3 using only choke. Even load is 0mA it all the time works with continuous choke current what was one of the reasons I selected it.
I used to work with audio stuff, as well as do PA and recordings back in the day.
It is not quite as simple as the switching frequency being outside of the audio band - unfortunately.
There are effects of regulation behaviour in SMPS that cause ripple in the audible band, and it is also possible to get interference between switching frequencies and sampling frequencies of AD-converters which mirror / fold down into the audible band.
When you get down to the -90dB and lower noise floors you want in a recording environment, there is quite some effort needed to filter out the high frequencies well enough.
So it is often easier to go analog to make things quiet. Then you mostly have the 50/100Hz ripple to deal with, and that is easier to deal with and filter with regulators and OP-amps (power supply rejection ratio, common mode rejection ratio) than tens or hundreds of kHz.
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While I understand the concern, I suspect that it might not be as necessary as you think. I assume that the current involved is <100 mA (but even if it is not): If you are interested in trying a different approach, buy a few large diameter (4-6 cm?) toroid cores made of high permeability ferrite for broadband transformers. Wind many turns of the power adapter output cable neatly around the core in a single layer, keeping the input end away from the output end. This will construct a common mode choke. I would also put a relatively large value (10 uF) 1206 size or 1210 size chip ceramic across the voltage where you connect the power supply output into your board. That capacitor will help suppress higher frequency noise.
Some years ago I bought a cheap 300W lab bench adjustable power supply. The output of this thing is noisy enough to be a real problem for a lot of my electronics work. It would be analogous to evaluating audio equipment out on a busy airport runway. So I wound a big common mode choke using AWG12 wire. The output then goes into a couple of low ESR electrolytic capacitors. I have this hanging on the front panel of the power supply. It looks ugly but it really knocks the noise down… I thought I had a photo but cannot find it at the moment.
I appreciate all the contributions you are giving me and I will use them to see which options are best for me for the project.
As greg_m says, I have a limited place to put the source, it has to go inside the pedal board and it would be less than 20 cm from the nearest pedal. I’m not a professional guitarist and I do this more as a hobby than as a work necessity, so it doesn’t have to be “pretty” but it does work, and the better it works, the better.
At least I have managed to recognize the spice model of the LM78xx, now I am with the rectifier bridges (which the simulator does not recognize either) and reading/learning everything related to transformers.
Again, thank you very much everyone for the help.
Regards!
I always built linear supplies into my designs. But these days I use a high quality module instead. The advantages out weigh the linear supply.
take a look at this:
https://www.mouser.com/ProductDetail/MEAN-WELL/IRM-03-9S?qs=NKmfXavxMayGO67ISbg87g%3D%3D
9V DC @ over 300mA from any input voltage from 85-264. With short circuit protection and fully isolated. At $8 I can’t build a supply with discreet parts that matches the performance.
I use the 20W 12V version to heat 3 12AX7’s. I’ve tested it down to 72V AC input.
If you’re new to electronics, definitely learn how to design a power supply. It will serve you well. Lot’s of good advice in this thread on that.
I will close this now as its not rally KiCad related.
There are other forums for basic electronics design