Make your own DIY power supply: yay or nay?

Let's be honest: buying a power supply is not the funniest thing ever.

It is quite expensive (and I have to admit that I would have prefered to add another fuzz that I do not need a nice pedal to my pedalboard than a power supply! 😁) and differences between the several models on the market is not very obvious...

So I asked myself: is it possible to make a DIY power supply?

Power Supply Carl Martin Pro Power

In this blog post, I will explain how a power supply work, what are the good criterias to choose one from an electronics point of view and if it is a good idea to make one yourself. Let's go!




How does a power supply work?

A power supply has a simple role: transform the 220V from your power outlet into a multitude of 9V DC outputs for your pedals.

Easy? Not really! Let's dive into the subject by looking inside my power supply, the Carl Martin Pro Power:
Carl Martin Pro Power gutshot inside

As you can see, it is quite crowded inside!

The main element is the transformer.

Not this one of course 😁 (badum tss!)
Tranformer

But rather the big squared blue component in the middle of the power supply.

As the name implies, it can tranform the 220V alternative current from your power outlet into a smaller voltage. It is a R10 transformer, which delivers a 15V output.

But our pedals need Direct Current (DC)! To go from AC to DC, usually a diode bridge is used. The remaining current is stabilized by capacitors, which generates a DC current, which has a lot of remaining ripples.

To make it smoother, there are two voltage regulators that you can see here:
Regulators Power Supply

You may already have used regulators in a guitar effects. If so, you should have noticed something: they are huged!

Indeed, they provide a high 1.5A current each! They are LM317 and are used to provide enough current for all the outputs of the power supply, The Carl Martin Pro Power has two 500 mA outputs and six 100 mA outputsm which makes a 1600 mA total, below the max 3 A that these can provide.

You can see that they have huge heat sinks, which touch the enclosure when it is closed. They are very important because regulators dissipate a LOT of heat! 1.5W dissipated can generate up to 100°C in heat. Thus, it is essential to have a good system of heat dissipation to avoid starting a fire!

You can also see a lot of electrolytic capacitors:

Power supply capcitors

All these capacitors fill the same purpose: filter the power supply! They will eliminate the last ripples of AC current that could still be there to avoid 50Hz noise in your pedals, You can see that there is at least one per output.

 Too long, did not read: this happen in a power supply: 220 alternative current from your power outlet is transformed into 15 V AC by a transformer, then in DC by a bridge rectifier. The remaining DC current is stabilized by regulators. The 9V DC is then filtered by a lot of electrolytic capacitors,.


Soooo... What is a GOOD power supply then?

Of course, there are good and bad power supplies.

Of course, one important thing to look after is the number of outputs and their delivered current intensity, but from the electronics point of view, there are two main things to consider.

1. Filtering quality

The electrolytic capacitors that are used for filtering and the type of filtering circuit they are used in will determine the overall noise output of the power supply.

The filtering is not the same in every power supply and can generate differences in term of noise. However, manufacturers do not always include the noise output, and without sophisticated instruments it is quite hard to measure...

As always, it would be great if we could have a little more transparency from manufacturers!

2. The type of transformer

Transformers can emit electromagnetic waves. Your cables are like antennas that will capt it, which will generate noise....  Depending on the transformer type, there will be more or less noise.

Usually, guitar pedal power supplies use a R core transformer that have low electromagnetic emission compared to other transformers like toroidal transformers. The Carl Martin Pro Power has a R core transformer for instance.

Voodoo lab uses a "custom thoroidal transformer", which reduces noise but is not optimal in my opinion.

Strymon has taken a different way by using a switch mode power supply in their Ojaj and Zuma power supplies, which generates far less electromagnetic emissions.
Strymon Ojaj


And it works! Look at this video:





DIY power supply: feasible?

In short, the answer is: yes but you should not.

Making a functional power supply is quite easy. Making an efficient, safe and noiseless power supply is far more difficult!

Indeed; you HAVE to be very cautious about overheating. Regulators generate a lot of heat and can easily start a fire in your system or worse in your housing!

There is also an electrical safety risk. You have to include all the safety elements that insure your safety while using the power supply: fuses, grounding, circuit breaker...

That is why all power supplies are certified CE, which guaranties electrical and fire safety:

CE norm

Another problem is the enclosure. They are unfortunately not standard enclosures.

Finally, there are a lot of chance that the performances of your power supply will be quite low compared to commercial ones.

That is why I would suggest you to simply buy a CE certified power supply with isolated outputs.

I think that my Carl Martin Pro Power is really good and not too expensive. If you want the top notch of power supplies, the Strymon Zuma or Strymon Ojaj are simply the best in class.



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7 Comment
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Should the output current not be taken into account? Depending on the pedals used, send 500 mA or 100 mA has no influence?
If Yes, the Strymon seems more suitable for digital pedals (more greedy) with his >500ma output.
The Truetone 1 Spot Pro CS12 power supply seems to be most versatile.

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Thanks Benoit, but what do you think about making many "9v" from a single "12v" like this?
http://guitar-fx-layouts.42897.x6.nabble.com/Custom-Voodoo-Labs-Pedal-Power-2-Plus-td8192i60.html

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Hi!

Few corrections here.


>The Carl Martin Pro Power has two 500 mA outputs

300mA


>they have huge heat sinks, which touch the enclosure when it is closed

They don't, but if they do, then it's a very bad engeneering practice.

The manufacturer claims outputs are isolated, which means they are floating. If they touch each other or the enclosure, then they become not isolated. Those to-220s don't have isolated tabs or any sort of electrical isolation between them and heat sinks. This is also bad.


>Regulators generate a lot of heat and can easily start a fire in your system or worse in your housing!

They do generate heat but they can't start fire.
All modern regulators have TOP. This is mandatory feature to comply with CE.


>circuit breaker

No circuit breakers are present in any commercially available PSU :)
I guess, you were talking abour your in-house electrical box. Still not sure why.


>I think that my Carl Martin Pro Power is really good

Can't aree. They a poorly designed, lack additional protection and won't last that long compared to other branded PSUs.


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I agree on all accounts with plush.
Additionally, a PSU with only one regulator (per voltage) should not have Pro in it's name. It is acting as a fancy daisy chain and (star wiring organization aside) one acts as (cheaper?) OneSpot.

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Thank you for your valuable comments! Glad to see experienced readers on my blog as well !

Heatsinks are connected to TO220 ground?? Did not know that!

I was actually wondering how a power supply could have isolated outputs with only 2 regulators... It is still sold as "isolated outputs"... I am going to shoot a mail to Carl Martin foxes to know how it is possible.

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This comment has been removed by the author. - Hapus
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I guess it has bunch of low power surface mount regulators on the back side of the board. Considering the number of bridge rectifiers used, this seems quite the solution ;)

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