Hi there, it's been a while that I didn't post a review and I've been messing around with third party USB PSU's for quite some time now(I'd even dare calling it an OCD at this point )....several followers of my Stello U3 thread asked me for further details and other Stello U3/DP1 claimed to hear drastic SQ improvements with cleaner PSU's so here we go! I'm only glad to share my modest "trial and error" real-world experience with feeding a cleaner PSU to USB audiophile equipment on my favorite audio-related forum
Long story short, after all the aforementioned "trial and error" I went through, google was kind enough to direct me to this thread that explains rather clearly what I had been up to on my side: http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=111159
So we're talking about this $2 little fella that saves the day: http://www.flyteccomputers.com/details.cfm?wid=432
Mikrotik is a company that deals with WiFi routers and such, so this cable comes with all the shielding you would expect from a USB 2.0 compliant cable. Again, these ppl sell wireless routers that more than likely end up in giant strongly EMI/RFI polluted rooms so they know a thing or two about shielding and this $2 winner has always worked flawlessly IME(up to 24/192 of course).
The only fatal issues in the audioasylum guy's experiments are that:
1) All the pins of that Y cable are connected because it was initially designed to power USB devices straight off their routers(whose USB ports aren't powered at all), so you will have to break the +5V pin on the computer side:
in fact that I may have to re-run my room correction measurements
The stock Y cable it came with was wayyyy too long, really really bright sounding and unbearably colored on the "Stello Eximus DP-1"(I wouldn't be surprised if it were silver based for that matter). So I knitted myself my own using a modded good ole copper "USB Injector" cable:
Pardo is using cheapo 2 pins round connectors that will more than likely oxidize to death, and even the PSU user manual it comes with advises to unplug and replug it several times in a row every few months as a precaution, huh. Kingrex overcame this issue by using a gold plated 3pins Neutrik XLR connection on their MK2 PSU, but more on this later =)
Most everyone in mid/high end audio will tell you that we are merely listening to the PSU, and even Pardo's website makes clear that the PSU is what colors the sound the most in his experience....hard to deny, as his PSU changed the sound drastically! Too bad deep bass appeared so colored, the SS felt like a stadium hall with barely anything in the center anymore and trebles were completely out of hand
So at this point, I also had the option of going with batteries but they come with their own issues:
1) the cheap ebay battery-based PSU's use nasty SMSP voltage regulators
2) most batteries have to be recharged every day or so, so you're SOL if you forget...or you have to buy two PSU's and reload one while using the other: headaches ahead.
3) these things will age rather quickly if you never turn off your DAC(as I do because I can't be hassled to wait for the darn thing to "warm up" in order to sound its best), and +1 year down the road these might not last that long anymore due to the constant loading cycles. Also, they tend to use relays that will make loud clicking noises at the end of their loading cycles and there is nothing I hate more than random relay clicks.
Luckily for us, the affordable 5V PSU consumer market bloomed in order to satisfy the Logitech SqueezeBox community, and the same "Kingrex MK2 PSU" name kept coming back on SB forums....many users agreed that it sounded really great on their SB rigs, that its markup wasn't stellar and that being 3A it could feed a whole bunch of USB storage devices plugged onto the SB.
There are many pro reviews that confirm that you get serious gear for your money, such as this one: http://www.digitalaudioblog.com/2011/05/review-kingrex-psu-mk2.html
What's in the heavy black box:
Specs as follow:
Transformer: 48VA toroidal type
Voltage regulatory circuit: 5x2200uF at AC input stage
3x4700uF at DC output stage
6N Furukawa PCOCC wiring
The nice thing about toroidal transformers is that they provide you with partial galvanic isolation from the mains, nothing to sneeze at. And the lighter the load, the lower the ripple hence the whole point of using an oversized 3A PSU.
Being able to output up to 3A also means that you could always use an extra Y cable and feed several pieces of equipment at once, or if you're lucky enough to have a DAC that feeds 5VDC(the "Calyx DAC 24/192" comes to mind) and runs a bus-powered USB controller, you could kill two birds with one stone as this 3A PSU would easily feed both simultaneously, and under a light load at that
I see that there are also SqueezeBox custom firmwares that allow async USB(with the M-DAC for instance), so you could use this 3A PSU to feed both the SB itself and the USB chip of your DAC =)
All this said, I was sold and decided to pull the trigger on this very promising 5VDC/3A PSU(£215 in the UK), soldered a Neutrik 3 pins gold plated XLR onto a pimped USB Injector and there ya go:
I like short DC cables and hard soldered connections, so it was only a matter of using a multimeter in order to find out which of the 2 wires on the PSU side of the "USB Injector" cable were GROUND and 5VCC, a bit of Cardas Eutectic Solder, a small piece of heatshrink later and we were in business
To make it perfectly clear, 6moons and Linnenberg Audio did confirm that the PSU ground and USB ground have to be shared.
The ground is not something we should be afraid of, as TI nailed down rather clearly writing a whole white paper about it(I'll update this review with the link later, as I don't currently have it handy).
My usual final test with a $10 USB dongle in order to ensure that its status LED would light up and that it's all good and won't fry my DP1:
Bang/bucks is huge on these Lacie cables IME and I do want to keep the PSU DC cable as short as possible, but you could also install the "USB Injector" cable on the host side and run a regular A/B USB cable to your audio device.
While you're at it, you may also wanna break the +5V pin on the computer side of the Lacie extension, I didn't try it myself yet but I keep it on the top of my "stuff to do when I'm bored" list ^^
There are also many Y USB cables, ranging from a grand to a few bucks(with a bit of DIY) so that could also be investigated.
So that's the Kingrex MK2 PSU with the pimped "USB Injector" cable and some $5 isolation feet(I was only glad to finally find a use to them ):
More pics of the PSU plugged onto my beloved DP1:
I should state that I use a rather good 400W Corsair PSU that was measured to output no more than 5.4mV ripple on its 5V rail under light load. The same review said that it was amongst the best at the time, and that was the very reason why I bought it. FWIR, latest PSU's are no better than this.
I should also make clear that the Stello U3 that is embedded into the "Eximus DP-1" takes care of the whole USB to I²S process, so basically the Kingrex PSU is being used for pretty much the whole digital side of the DP-1's USB input....hence the drastic SQ improvement that will have made all my efforts entirely worth it after all
So anyway, how does it sound then? Clearly not as utterly colored as the Pardo, but compared to the noisy computer power:
-deep bass is far more extended and a lot clearer, "less bloated" in two words
-SS has opened up rather drastically, but it's still entirely possible to play narrow mono(which wasn't possible at all on the Pardo IME)
-trebles and mids are much clearer and seem to be providing far more "resolution" to them. Mids are especially "thicker" sounding, which is most delightful on orthos.
-the sound is all around a lot more enjoyable, being less colored and far more refined....most delightful to listen to
Going back to the computer power is a big no-no and this PSU upgrade turns the reference DP1 into something beyond words.....really. People who claim that a clean PSU makes all the difference in the world on transparent gear are very much spot-on to my ears. And I can hear why the 6moons owner tries his luck with every PSU and Y cable he can put his hands on ^^
As a conclusion, I can only confirm that feeding the U3/DP1 with a linear PSU is a one-way ticket and that there is no chance you will ever consider going back to the shared ATX computer PSU power afterwards
Also, the Kingrex MK2 PSU doesn't get warm at all(even if you leave it on 24/7 as I do) and it doesn't hum or makes any whining noise whatsoever.
Finally, I hope to have helped shed some lights on how to use a linear PSU for USB operation to those who wanted to know more, and I can safely advise to give this Kingrex PSU a shot because bang/bucks is stellar IMHO
Edited by leeperry - 1/16/13 at 9:52am