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Issue with custom Raspberry power supply

officialsm

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Hi all,
I have a Raspberry (as described here https://www.audiosciencereview.com/forum/index.php?threads/improve-raspberry-4-streamer.22401/ ) and i bought a linear power supply. Previously i'm using a switching power supply.
Switching power supply was setted up around 5.28 Volts (5 Ampere) because i have installed a power management board (from Audiophonics) that drops down a little voltage. With this configuration no issue.

With new linear power supply i have frequently under voltage errors in syslog like this:

Under-voltage detected! (0x00050005)

i improved volts around 5.35 volts but still have issue.
Seems that nee power supply had not stable volts erogation and it drops down volts sometimes.
Raspberry and streaming works same but i would like to avoid this kind of errors.

Someone could help me to investigate?
Thank you so much
 

somebodyelse

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It seems like your linear PSU has poor voltage regulation, insufficient current capacity, or possibly both. What are the specifications of the linear PSU?
 
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officialsm

officialsm

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officialsm

officialsm

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Here reply from seller:

"this is a linear power supply. The power of your device is within 3.5A. This is not a fault. It is not a switching power supply. It is a linear power supply! The title and the selling post also have instructions "

I dont know if correct or not
 

somebodyelse

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I'm not seeing claims about regulation or noise in the specification, so they can say it works as specified. Unless you have an oscilloscope you probably won't be able to test any further, although it might be worth checking the resistance of the USB cable you use between it and the Pi.

This seems to be a good example of switching PSUs not necessarily being bad, and linear PSUs not necessarily being good.
 
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officialsm

officialsm

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I will try a different cable (I'm using a DC/DC 5.5 mm).
Do you think this voltage drops will affect system usb output or sound?
 

somebodyelse

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I will try a different cable (I'm using a DC/DC 5.5 mm).
Do you think this voltage drops will affect system usb output or sound?
It's probably not the cable that's the problem then. Some USB cables use wires that are too thin for the power connections to save a bit of money.
How can i measure it?
I should have thought about that before suggesting it - you probably don't have anything that can measure resistance that low.

I'd just use the SMPS you already have - from what you've said it doesn't seem to be causing any problems. If you have a good DAC the PSU is unlikely to make a difference anyway.
 

mcdn

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i can’t see a voltage regulator in the seller’s pictures, and if there was one it would need a big heat sink. what’s the audiophonics board you said you are using?

[edit] doh the big mosfet is probably part of a discrete regulator circuit?
 
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officialsm

officialsm

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mcdn

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A couple of the reviews of the Audiophonics device mention problems with voltage. It doesn’t have an obvious relay or power transistor so it could be the problem, maybe. Hard to tell as there aren’t markings that are visible on the transistor near the switched power output.
 
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officialsm

officialsm

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I swapped out othe cable i was using (very thin and solded by me) with cable provided with linear power supply and this seems to fix issue. I stremed a coupe of songs without under voltage errors on syslog (now i setted up voltage at 5.28 V as done in the past)
Thank you for helping me.
 
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officialsm

officialsm

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At the moment dropped down at 5.20 V and is working fine. So cable make difference.
 
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