I was doing a little reading on the power supply requirements for the RPi3B+ and the Allo Boss 1.2 DAC.
It seems the RPi3B+ draws quite a bit more current than the older Pi versions.
https://raspi.tv/2018/how-much-power-doe...asurements
From that, it looks like the Pi3B+ by itself draws up to 0.7A under load. Fortunately, audio streaming shouldn't put that much of a strain on the processor, right? 5VDC at 1A should still be plenty to power the Pi3B+. Use a psu rated for 2.5A for some headroom.
It looks like the Allo Boss DAC needs up to 0.6A. In the description of their i2s Isolator, they say:
"Isolator will... provide 5v/0.6A using... LT3042 LDOs."
https://allo.com/sparky/isolator.html
Since the Isolator is designed to be used with their DAC HATs, I figure 0.6A is enough for a Boss DAC. So once again, 1A is plenty.
That bodes well for this battery power bank idea. However, there is a gotcha. Apparently these power banks all use 3.6V batteries internally, with DC-DC boost converters to bring the voltage up to 5VDC.
I'm not sure if this is the exact type of device, but this looks like it might be what's used in these power banks:
https://www.monolithicpower.com/en/mp2637.html
If correct, that means there is switch-mode power supply stuff going on in these power banks too. That does not bode well for them being a significant improvement over a good SMPS.
And around and around we go. I need to take my power bank over to a buddy's place where we can put the output from the power bank and my SMPS on a 'scope and see if one is obviously less noisy than the other, both when it comes to 60Hz or 120Hz ripple and HF switching noise.
I'm thinking it still might be worth it to take a 12V 2A transformer, a worthy diode bridge rectifier, a couple of high-wattage power resistors, a few 4700uF 35V caps, and an LM317 on a heatsink, and just make a brute force 5VDC linear supply to power the DAC separately. If the LM317 is only called on to deliver 0.5A at most, it should work fine. Total power draw should be under 15W for the linear supply feeding the DAC only. The Pi could get the 2.4A power bank battery feed, I suppose.
Great, another project!
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It seems the RPi3B+ draws quite a bit more current than the older Pi versions.
https://raspi.tv/2018/how-much-power-doe...asurements
From that, it looks like the Pi3B+ by itself draws up to 0.7A under load. Fortunately, audio streaming shouldn't put that much of a strain on the processor, right? 5VDC at 1A should still be plenty to power the Pi3B+. Use a psu rated for 2.5A for some headroom.
It looks like the Allo Boss DAC needs up to 0.6A. In the description of their i2s Isolator, they say:
"Isolator will... provide 5v/0.6A using... LT3042 LDOs."
https://allo.com/sparky/isolator.html
Since the Isolator is designed to be used with their DAC HATs, I figure 0.6A is enough for a Boss DAC. So once again, 1A is plenty.
That bodes well for this battery power bank idea. However, there is a gotcha. Apparently these power banks all use 3.6V batteries internally, with DC-DC boost converters to bring the voltage up to 5VDC.
I'm not sure if this is the exact type of device, but this looks like it might be what's used in these power banks:
https://www.monolithicpower.com/en/mp2637.html
If correct, that means there is switch-mode power supply stuff going on in these power banks too. That does not bode well for them being a significant improvement over a good SMPS.
And around and around we go. I need to take my power bank over to a buddy's place where we can put the output from the power bank and my SMPS on a 'scope and see if one is obviously less noisy than the other, both when it comes to 60Hz or 120Hz ripple and HF switching noise.
I'm thinking it still might be worth it to take a 12V 2A transformer, a worthy diode bridge rectifier, a couple of high-wattage power resistors, a few 4700uF 35V caps, and an LM317 on a heatsink, and just make a brute force 5VDC linear supply to power the DAC separately. If the LM317 is only called on to deliver 0.5A at most, it should work fine. Total power draw should be under 15W for the linear supply feeding the DAC only. The Pi could get the 2.4A power bank battery feed, I suppose.
Great, another project!
--
