Linear Power Supplies for DACs/Amps

This is a discussion of upgrades for AMP’s and DAC’s using linear power supply units.

I am trying to find a used Paul Hynes SR4. Does anyone have any information about this PSU?

Happy Cake Day @Doc.

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Thank you! After reading your bio, we both grew up in similar times and have similar tastes, even to our preference for a clear and prominent high end. Thank you for the welcome. I hope we can get some guys interested in linear power supplies as the switched ones that come with a lot of DACs including mine (Qutest) can be considered as a last minute decision on the part of the production team. Good luck with your pulmonary situation. I am a retired ER physician. - been an audiophile all my life, migrating to a serious interest in headphone listening about 2007. My room system is now minimal on purpose.

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I’ve done a bunch of testing for this sort of thing over the years. Both for individual components and for systems. The outcomes of those tests have been highly consistent. In general they show that if you’re replacing an external switching PSU (e.g. a “wall wart” or other “brick”) with a linear one, then:

  • In components that are purely analog, with no additional switching supplies inside the device itself, then there can be a measurable change in performance. Though outside cases of poor internal regulation and poor initial PSU quality, those measurable changes rarely reach the level of audibility.

  • In components that do have additional internal switching supplies (most DACs for example, as they often need to do level shifting for different parts of the circuit), replacing their external PSUs has had no measurable effect on the output of the component at all. That has held in almost every case, even when the replacement linear PSU is demonstrably cleaner at its output than the switcher it replaces.

  • In systems where there is a mix of linear and switching supplies, for example an amplifier with a linear PSU and a DAC with an SMPS, replacing the SMPS with a high quality LPS made no difference to the output of the DAC, but did result in measurable changes in the output of the amplifier. This is due to the hash that SMPS can put back on the AC line affecting the amplifier.

Some specific examples …

Comparing an RME ADI-2 DAC fs using its included SMPS to the same DAC being fed by a) an unregulated battery supply, b) a regulated battery supply, c) an expensive LPS and d) a “priced like a new luxury car” lab supply, showed NO measurable difference at the output of the DAC.

The same was true with a Chord Hugo TT2 and a Chord Qutest.

Not only was there no measurable change at the output of the DAC, but as part of those comparisons I ran a proper blind comparison for the owners of those units, who’d claimed “night and day” differences in performance with the LPS vs. the SMPS. Yet listening blind, they absolutely could not tell them apart.

I did a similar test recently using a Chord DAVE equipped with a custom-made, and very expensive, external LPS unit that actually replaces the main internal SMPS vs. a stock DAVE. While there was no question that the output of that LPS was cleaner than the output of the internal SMPS, it too resulted in essentially no measurable change at the output of the DAC*. And, again, the owner, who swore blind that it was a huge upgrade, could not tell it apart from a stock DAVE in a blind listening comparison.

Now one case where making such a switch did have an effect, was with the Drop MCTH. Replacing it’s stock external SMPS with a good-quality LPS dropped the noise level from about -58 dB to -63 dB. That was easily measurable and, in the right circumstances, just barely audible. Though the LPS cost 20% more than the MCTH amplifier itself**.

Replacing the stock SMPS for the DAC that was feeding the MCTH in that case, resulted in no change in the DAC’s output at all. With the SMPS feeding the MCTH it resulted in no change in the output of the SYSTEM either. However, with the LPS feeding the MCTH, replacing the SMPS on the DAC resulted in another 2 dB improvement in the net noise level of the system as a whole.

Now, where it gets really interesting is that with both units running LPS supplies, moving the system to a different room (which was on a different electrical circuit) resulted in an INCREASE in noise over both units running their stock SMPS.

Long story short … replacing SMPS with LPS is not a panacea. It can have an effect. The effect can be audible. The effect can also be positive or negative. And this is highly dependent on the nature of the component and its nominal performance, as well as the system in which it operates.

Even in cases where there are differences, they’re usually very small and typically at levels that are pushing the limits of even potential, theoretical, audibility.

So, tread carefully, and if at all possible do a proper blind comparison before spending a significant portion of the cost of a unit on an " upgrade" LPS.

*The difference in measurements observed were within the realm of run-to-run differences.
**For the combined cost of these units, you could buy an amplifier that had 40 dB better noise and 60 dB better distortion figures.


Wonderful post. Thank you for your wisdom. (It will save me time and $$)!

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