I tried to be honest. I often laugh reading many feedback in the online forum discussion when they tried to answer a question about: "is it necessary to have a linear power supply for Raspberry Pi?"
Yes, we are talking Raspberry Pi as media player or NAS connected by a HAT to send the digital out to the better performance external DAC. Then will it improve the sound quality by only changing from cheap switching power supply to the linear? I guess you have find this same conversation in many forum as well.
I understand that buying a finished linear power supply product can be costly. Let's say the price of this mostly above US$100 and spending such that money seems totally useless because your opinion already broken from that forum feedback. They are saying that linear power supply for computer is not logical at all to give any benefit. Which in my opinion their feedback has nothing to do with practical experience, but only based on their subjective opinion. Period!
So I put US$20 on the table and made one for you. Let's begin:)
First things first, the ugly switching power supply comes with Raspberry Pi like I have here is should be throw immediately to trash can. Seriously, if you have an oscilloscope then you will find the high frequency DC noise is extremely high with this power supply unit. The risk when using it is not only decrease performance from your Raspberry Pi but potentially damaging the components inside for a long period of usage.
Like I said earlier, I spending that US$20 to make this regulated linear power supply. Again, people did misconception for years by saying just a linear power supply. Because linear is only using a transformer, rectifier and capacitor. This will not give the best result.
The correct name should be regulated linear power supply, means it should remove any DC noise at 50/60hz cycle generated by the power transformer. Traditionally by using a transistor and a Zener.
In this project, I will make this power supply more advance but still simple to follow.
As you can see the parts choice is not so critical. As long they are original, then they can be use in this project.
I spending US$5 for the transformer. It is used, dismantled from old Sony mini components audio system. The transformer rating is 25 VA and the secondary output is AC 9 volt.
The main filter capacitors is 3.300uF/25v Nichicon FW, the output smoothing capacitors is 330uF/6v Sanyo Os-con and the regulated filter capacitor is 22uF/16v BC components.
The diodes I using here is the high quality Vishay each capable up to 2 ampere of current.
Again all components are not strictly to follow. You can variate many components that suit you in this project.
This is the main components to regulating the DC. It is LT1083CP. This is 3 pin positive regulator just like popular LM317, but this LT1083 is capable to deliver maximum 7 ampere current output. Because we need at least 3 ampere output at 5 volt for the Raspberry Pi, so theoretically the regulator should greater at least 30% than the current requirement. The more head room for the regulator IC will regulate the ripple better as per datasheet.
And this is the schematic recommendation for 5 volt power supply as per original datasheet.
I am using 500 ohm trim pot replacing schematic suggestion 365 ohm because it is more easy to obtain.
And here is the result.
It is really simple to connect all components by point-to-point connection in the universal board like this.
Next I put all components inside cheap plastic power supply case. Not a fancy stuff here because I want the cost to build this power supply is affordable.
I prefer spending more money on the good quality cables. I am using OEM laptop power supply cable here that cost me US$2 for 3 meter length. The cable quality is very good, same like on your laptop power supply cable.
Since the Raspberry Pi require the power supply input by using a micro USB connection, then I cut the end of the cable and replace it by this micro USB cable. This cable is dismantled from Sony Car Charger micro USB cable that also very good quality.
I also dial the trim-pot to get the precise 5 volt output. I make sure the polarity on the micro USB are correct. Then I can close the lid, this regulated linear power supply for Raspberry Pi is now ready.
That's it! I only spending US$20 and you can make one for yourself!
Please test this power supply by yourself, then come back to the online forum discussion about this topic. Now you can give proper answer for them that this regulated linear power supply are make improvement in sound quality or not.
For me, this regulated power supply significantly impact to the better sound. Once again, I could said you will spending a worthy US$20 for this regulated linear power supply.
I playing the same music, in the same audio system, the background sound seems more quitter, the sound-stage get wider, and the detail comes to lives better than when using that crappy switching power supply.
Your Raspberry Pi can lives happy now.
And you as well:)
Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.
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