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What is a "poor" PSU for DAC2HD?

Andreas Studer

August 13, 2023 10:18

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Hello all

I have a beginner question. I tried to find that out here but it seems to be a hard question to figure out for an absolute beginner...

The article https://www.hifiberry.com/blog/techtalk-power-supply-matters/ discusses the matter of a good PSU. However, I didn't find what a "poor" PSU really is. As there is an area of "don't go there", I didn't found any indications where the audio quicksand begins.

My plan is to use one of the Meanwell PSU for an own project (e.g. something like https://www.distrelec.ch/schaltnetzteil-44-8w-5v-2a-mean-well-pd-45b/p/30372477 or even https://www.distrelec.ch/ac-dc-netzteil-fuer-medizinische-anwendungen-15w-5v-3a-traco-power-tpp-15-105/p/30154077). But I don't have any clue if that is good enough to start or simply too bad from the  beginning. 

I guess the PSU offered directly from Hifiberry is the minimal requirement, as it is rater favorable and obviously a switching PSU. But beside of the technical spec that it delivers 5.1 V and 3A I don't find any further technical specs, like Vpp ripple as an example.

Yes, linear PSU's are the best for audio. But first they're rather expensive and second the article on the website above indicates the DAC2HD can handle some dirt on the power; obviously a good switching PSU can be good enough for a beginner. 

So what is the minimum technical specifications to keep for a PSU with Hifiberry DAC2HD? E.g. what are the full technical specs of the one offered by Hifiberry?

Cheers

Andreas

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3 comments

• 0
  
  HiFiBerry team August 14, 2023 04:50

  >Yes, linear PSU's are the best for audio.
  
  No, this is a common misconception. Most so-called "linear" power supplies are not "linear", but switching power supplies thatswitch at a frequency of 100Hz (the mains frequency). This frequency is within the audible frequency range. While "normal" switch mode power supplies switching frequency is outside (usually >50kHz).

  A good power supply has low ripple and noise. I can't say anything about the specific power supply you have linked.  In genereal we have good experience with Meanwell power supplies. Howeverm if you're not experienced with this kind of thing, we strongly recommend not to use any open-frame power supplies like this as there are multiple components that run 230V mains frequency. Not just touching these, but a simple shortage to a metal case can be deadly!

• 0
  
  Andreas Studer August 14, 2023 20:05

  Hello Hifiberry team

  I see. The comparison with the 100Hz (which can't go away completely; no matter what you do) is a fair point. 

  Basically I have an education in such things. But I'm not experienced in the audio area and what PSU to choose. That was the point.

  The linked page of hifiberry explains there is a filter on the DAC2HD for such things, but it's not clear for me where the filter has its limits.

  I see fairly prominent examples in audio streaming that are far from using linear power supplies. For example, the Cambridge MXN10 uses a Meanwell IRM-20-5 power supply (yes, even the "big" AXN10, which actually just has a bigger case). True, this is a good switched power supply. But it doesn't even have a noticeably good ripple value (200 mVp-p). Others use a plug-in power supply, which are obviously only switch-mode power supplies, and they're rarely in an excellent range.

  Thanks for the answer.

• 0
  
  HiFiBerry team August 18, 2023 05:16

  We recommend <100mV ripple (10MHz bandwidth), but a bit more even more isn't a big deal. Power consumption can be highly dynamic. Therefore there isn't a simple spec that you can just look up in the data sheet. However, we have had very good experiences with Meanwell power supplies in general.