Hi
I have a nice linear audio power supply, 27 watts. However, running a Pi 5, a cooler, a Is2 Dac and a screen, gives me the low voltage indication .
So, I need to supplement power. I am thinking of getting a cheaper switching power supply to add to the system.
My question. Where should I connect the the nice linear audio supply and where to connect the ordinary switching supply?
thanks
I would connect the linear to the Rpi5, the impulse - to the DAC or monitor
How is that possible? 27 Watts must be plenty for such setup…
Maybe it also has a monitor connected to USB? We don’t know anything
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In basic,
Powering a USB screen from USB is a no-go and will generate Low voltage errors.
Power from the LPS, 1 cable to the rPi, 1 Cable to the DAC and one cable to the Screen.
So split it before you connect anything .
If it still generates Low Voltage errors, then I suspect a cheap Chinees LPS. Where 27 Chinees Watts translates to 15 rest of the world Watts.
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Yes, I do have a big monitor that is connect via the hdmi port on the rpi.
It is an old monitor that needs to be plugged in to ac and to the pi via the HDMI port.
Its a great peppymeter display 
Maybe that’s what is sucking all the power?
this monitor has its own power supply. I think it’s a TV. First check what happens when you connect the DAC to its own power supply. If you still don’t have enough power: see what @wheaten wrote
See this thread and possible solution regarding powering Rpi5 with non-official PSU: Powering the Raspberry Pi 5
Quote from jamesh (Raspberry Pi Engineer & Forum Moderator): “If you don’t tell the Pi that the power supply is 5a capable, then you will get warning messages as the Pi then assumes a 3A maximum.”
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Thank-you. That’s very interesting. Its a Pi5 so maybe thats whats going on.
So I posted a PSU related question that I think is similar to this (no responses there yet).
I’m thinking about doing a PSU like the OP (actually my engineer brother will do it for me) but with my Pi5 fully loaded and running Volumio it’s pulling this:
That seems quite low. 1.487 amps for the dac and a pie 5. Do you have a screen connected as well?
I don’t know if I would trust those numbers to be accurate.
So the DAC is connected via USB but it’s powered by it’s own PSU.
Here’s everything that’s connected:
Pi5 4GB
Official Pi5 PSU
5.5" AMOLED Display
USB Connections:
- Touch display
- USB Out to SMSL A50 Pro
- 2TB M2 SSD on USB enclosure
- External USB WiFi Dongle
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I ordered that little tool. I’m building something very similar. I’ll let you know my readings.
So I ordered a “better” tool just to see what the readings would be:
Some differences - using this one the Watts did jump to around 11 at boot but once settled and running they’re all pretty much the same, which begs the question:
Am I doing something completely wrong or is the “official” Pi 5 PSU total overkill for a situation like this?
Running current is not the startup current. the latter is the on causing issues.
For Example a generic USB disk varies between 2-4A, without the enclosure.
the rpi will add 1-2A, Then there is a Display and dongle.
So the peak current might be > 5A, causing a safety guard to become active, lowering the USB Voltage.
Which causes unstable behaviour.
So when booted and running the current is < 2A vs 5+A on booting.
So I actually need a larger PSU for this setup?
What sort of “unstable behavior” should I be looking/listening for?
Can’t tell, no idea what the peak current is, I mentioned it as a pointer.
But I would recommend to power the separate parts via the PSU, not the rPi
How would I power the external SSD and the WiFi adapter since they connect directly to the Pi?
I actually think that the SMSL amp is “giving” power back to the Pi/display - when I unplug the Pi PSU the display still has a green light but it goes off when I pull the USB cable that is servicing the audio to the amp.
Is there a tool/device out there that can detect/measure that?
if the dongle you bought has a min/max function yes.
I expect that the USB M2 thingy is drawing to much current.
mmm, that makes it complex…
Get your self a powered USB hub.
Pi USB Out to hub.
Hub to USB peripherals.