So I've got a few older pcbs for a low voltage tube headphone amp I built years ago - the Millett Hybrid - and was thinking I could put one together with my Pi3,IQAudio hat DAC, and WD passport HDD all in the same small enclosure and run it off the HPA's supply to use at work. The HPA needs 24VDC/750mA. I currently use the Pi/hat/hdd as a player using a 5V/2A pi wallwart.

Is there a good way to drop the 24VDC to 5VDC to run the Pi/DAC/HDD without massive heat dissipation? Also, would I need to look at filtering the power to the Pi to keep the noise down since both the amp and Pi will be tied to the same PS?

I used a LM317 regulator with a 24VDC wallwart for the amp I built in the past. It was well filtered and worked well (Tangent TREAD regulator). I thought maybe that for the amp and a buck converter for the pi. My concern is any noise from the buck.

The whole thing will be going in a 6” x 9” enclosure. The amp pcb is 4x6”. Here are some pics of my old amp (it’s just the top half enclosure) with the small regulator and the bare pcb in the enclosure for size reference.

LM317 regulator


bare pcb

  • Not sure if this will pass as "on topic", but: You shouldn't have any issues using a 24-5 SMPS for your RPi here. They often use SMPS in audio amplifiers, so there's no reason you couldn't use it to power your RPi. Pay attention to wiring layout & see the RPi is not "starved" for power with small-gauge wiring. – Seamus Jan 27 at 5:42
  • I’d like to fit everything into the enclosure. Is there an smps that is smaller than 2.5” x 4”? – Blooze Jan 27 at 15:00
  • Oh yeah - thousands of them I'd guess. Have a look at Mouser, or Arrow Electronics - or any of the larger US distributors. If you're not familiar & knowledgeable on electronics in general, I would suggest you avoid the "junk traders" at Amazon, eBay, etc... they're not all selling junk, but it might be hard to tell the junk from the quality. – Seamus Jan 27 at 20:12

Look for a stepdown converter. You can get them by the kilo on ebay. I've been using them for quite many years on industrial applications. You can get them for like 2-3£ and they are small... The one I was looking was Size: L_59mm * W_21mm * H_17mm Now days I am using the ZB15-24-5S. It's a bit pricier but it's pcb mounted and I was looking for something that was on a steady supply and of-course something that can accept more than 24V input. Example

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