I have had the NOS1 since January 2013 and have been very happy with the SQ that was added to my audio chain. It replaced a Bryston BDA-1 dac that I enjoyed very much before.
While I was using this previous dac, I tried a few power supplies for the Audiophilleo 2 USB to SPDIF converter, that was directly plugged at the dac input. This converter is normally powered by the USB 5 volts that comes from the PC. To improve the SQ, I got an Aqvox USB power supply, that replaced the "noisy" power with a clean 1mv ripple power.
Then I heard about the iFi iUSB power supply, with its 0.1uV ripple - better than the Aqvox. Bought it.
I "thought" that each change was doing something good. I am using "thought" in quotes because there were slight changes, but I could not really turn them into images. Anyway, if I did not try, I would never have known...
When I removed the AP2 + Bryston in favour of the NOS1, I had concerns about putting anything in between the pc and the dac. It seemed that Peter had thoroughly thought about every aspect between pc and dac. XXHighEnd is so musical and adjustable that putting anything else would have been "heretic".
The Aqvox was not needed anymore, so was the iUSB.
And for the first time, I could use the Sotm PCIe USB card that had been idling in my PC, because there were latency and/or buffer problems (Blue Screens) with the Audiophilleo before.
With the Sotm, I can cut the power off (5V) (there is a switch right beside the USB connection on the Sotm) after XXHE has established a connection with the NOS1.
But after a while I decided to put the iUSB "back to work". I removed the SSD that was in my music pc and put it in an external enclosure, like the music hdd (2TB, 7200rpm). The two of them are connected to the pc through Esata. The SSD holds W8/64 pro and XXHE. So now the iUSB powers the SSD.
Did I hear an improvement ? Not really.
5 days ago, I received another linear power supply, this time for my music hdd. While the price of that linear power supply is twice the value of the drive + the enclosure, I again took a chance.
Let me put it this way: I am not very sensitive to slight variations in SQ, way less than many of the posters in this forum. I tried very few USB cables, had paid quite an amount of money for interconnects and AC cables... But NO, I did not really feel that there was an improvement in SQ. I can't specify if a USB port is better than another, not even if I compare them with the Sotm USB card... I apply recommended tweaks, try a few others, appreciate what I can learn from fellow posters. As for my hearing abilities, well all I can say is that I am happy to still be able to hear something, as I have abused my ears many eons ago.
With this in mind, I was not expecting to hear a damn difference.
I have read a lot of descriptions about one's perceptions but to image what I perceive now is hard for me. The nearest approximation that I can give would be something like "Tthere is AIR between the notes"... It may not be it, but it is surprisingly good. The LF are tight, the notes are clearer... It is as if a "sizzling" was removed.
In each step of my journey, I have heard some improvement through time, but at a certain point all has been subtle and my expectation bias is not high. Most of the time, I would say that except for XXHE and the NOS1, many expenses were done for not much.
If you have the chance to find a linear power supply that will fit with your budget, try it. The power supply I bought is a TeddyPardo brand, model "Teddy12/4"). There is also the "Teddy12/2" power supply. I chose the 4 amps version because it could accommodate more powerful devices (48 watts max), but the 2 amps (24 watts) will certainly fit perfectly for a hard drive. As long as the DC voltage output is the same as the wall wart it replaces, and the amperage is equal or higher, the power supply should be perfect for the job.
There are other brands and I am quite sure that they would achieve what I am perceiving now.
This TeddyPardo power supply is expensive if you compare its price vs the price of a hard drive + its enclosure. But if I can hear what I hear now, you will most likely hear something too.
I don't like to write superlatives, because I don't feel it is necessary. I can only try to contribute with fellow audiophiles what I am perceiving now.
A linear power supply for the PC ? I hope there will one powerful enough someday
Alain
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