New HD Plex 200W linear PSU

[octaviars]

Some fun reading regarding PSU for computers.

I have my own plans to use a Paul Hynes to power a HDPlex DT-ATX converter but perhaps that is overkill when the DC-ATX converter has so much ripple but low impedance may still be a very good thing.

https://www.computeraudiophile.com/forum...ent=642110

So it would seem that moving up to this larger microATX ASRock motherboard will bring with it both good things and bad but hopefully, the positives will outweigh the negatives.
 
The Good:
Two PCIE 3.0 slots that allow the most direct access to the CPU that is possible. These slots have the same low latency access to the CPU as RAM. All the other buses must go through the Platform Controller Hub to access the CPU. One slot will be used for my Intel dual LAN card and the other slot will be used for my SATA to PCIE card where my OS drive and one of my data drives will connect.
 
The Bad:
More noise.
 
I can power the CPU directly with a 12V lead from my SR7. This should be a significant advantage over my Mac Mini and hopefully will help negate some potentially serious disadvantages.
 
My mATX motherboard will require a high current 5V, 3.3V and 5V standby rail in addition to possibly another legacy rail and so Paul Hynes has told me that I will not be able to use my SR7 to directly power these rails without a DC-ATX converter. This means I have placed an order for the HDPlex 300W-HiFi-DC-ATX converter based on the recommendation of many. From my search, I have not found another DC-ATX converter that is convincingly better. With this HDPlex 300W-HiFi-DC-ATX converter in place, I can then use my SR7 to feed it. I have had another SR7 on order since January and Paul has told me it should be finally ready to ship in the next week or two. Upon hearing my dilemma, Paul was kind enough to agree to convert my 12V rail to a 19V rail so that I can feed the HDPlex DC-ATX converter the voltage it requires. He has also agreed to fabricate for me a high performance 24-pin to 24-pin ATX cable so that I can connect the HDPlex DC-ATX converter to my motherboard. I really can't say enough great things about Paul. For those with custom LPSU needs, I can't recommend him more highly.
 
Anyway, now that I'm on this path, I did some digging around and here are some comparative values. They don't guarantee how good something will sound but they do provide perspective.
 
Since only noise floor data is provided by most manufacturers, I've gone ahead and listed what I have found. Noise is listed in mV and the lower the value, the better:
 
Generic switching PSU ~ 60mV
EVGA SuperNova 1.6kW Platinum ATX PSU (100% load) ~ 12.4 - 22.7mV
EVGA SuperNova 1.6kW Platinum ATX PSU (20% load) ~ 4.0 - 13.4mV
Corsair AX1200i 1.2kW Platinum ATX PSU (100% load) ~ 7.3 - 13.7mV
Corsair AX1200i 1.2kW Platinum ATX PSU (20% load) ~ 5.6 - 11.4mV
HDPlex 400W ATX LPSU (100% load) ~ 3-5mV
HDPlex 100W LPSU with LT1083 regulators (100% load) ~ 2-3mV
Paul Hynes SR7 (100% load from 10Hz to 100KHz) <4uV = <0.004mV
 
Compared against either HDPlex LPSUs, the SR7 is in the order of being nearly 1000x quieter and nearly 10,000x quieter than a generic switching PSU.
 
Unfortunately, because I will have to use the HDPlex 300W-HiFi-DC-ATX converter which uses regulators with measured ripple values of 10mV (more than 2000x noisier than the SR7), the ultra low noise floor of the SR7 will be buried by the much higher noise floor of the HDPlex DC-ATX converter. From a noise standpoint, almost any decent switching PSU may possibly sound just as good because this converter will be the limiting factor.
 
This then raises the question of just how noisy the numerous switching regulators buried within the motherboard are. Quite possibly, they may be even noisier than 10mV and so from a noise standpoint, especially with a motherboard's 3.3V rail (which is the noisiest rail on an ATX motherboard), all of this may be moot. Quite depressing.
 
CONCLUSIONS?
1. We really need someone to design an audiophile-class motherboard without noisy switching regulators.
2. In the absence of such a motherboard, because noise is potentially additive, it probably still makes sense to use a low noise PSU but its benefits will be at least partially negated by the noise created by the motherboard (or the DC-ATX converter).
3. It would seem that ATX power supplies designed for high power output (specifically high current output) will generally also have a higher noise floor but in this regard, the HDPlex ATX LPSU stands out as being exceptional.
4. Noise aside, low impedance still matters. To my ears, this may be a more important quality because with the aid of grounding boxes, noise filters and galvanic isolating devices, there are ways to mitigate noise but no way to undo the suffocating impact of a high impedance PSU. It's quite possible the EVGA excels here but there's no way to know except through comparative listening since no measurements are available.