 The HB project and the HB channel are supported by AudioQuest. Experience the difference. Setting up a review of external power supplies appears to be an interesting adventure. It was not easy to get review samples, especially the affordable ones. Then finding measurements within the possibilities of my measurement equipment that seemed relevant for the sound quality and finally deciding what audio equipment to use for the actual listening test. This series of reviews has been postponed several times to come to results that are relevant for you, the viewer. Initially I also had some vintage power supplies planned to include but they were not able to deliver sufficient current for this test. In this video I will review the original Raspberry Pi 2B power supply, the iFi iPower 5V, the Audiophonix 5V 25VA low-noise linear power supply and the S-booster BTOW PMP ECO 5-6V. In this first review I will use the Raspberry Pi 2B with the HiFiBerry DAC Plus Pro as the benchmark equipment to power. The Raspberry Pi was chosen for its popularity and the HiFiBerry DAC Plus Pro board for a number of reasons. I wanted to use a DAC board and not an SPDIF board since a DAC board will be more critical. I also wanted to use the modification for power supply I use on the HiFiBerry DigiPlus as described in HiFiBerry DigiPlus Part 2 tweaks and further on in this review where I solder a header onto the print to connect the power supply to the HiFiBerry board instead of the Raspberry Pi. The Pi is then powered from the HiFiBerry board. Let's look at the power supplies on test here. This is the wall wart that Raspberry Pi sold for the Raspberry Pi 2B. It's a simple general purpose switching mode power supply that ends in a micro USB connector so it can be plugged directly into the Raspberry Pi. So this power supply was the only one that was not connected to the DAC and was added to a reference for those that use a standard power supply and way of connecting. The price back then was € 895. This is a wall wart type switching mode power supply and is available in 5, 9, 12 and 15 volts versions. The plastic housing is vulcanized and cannot be opened. On their side they claim to have lower noise and audiophile linear power supplies and although I didn't find that in my measurements, I did see a rather clean 5 volts. The iPower comes with a set of adapter plugs to fit all kinds of devices. The price is € 49. This power supply comes in a good looking aluminium housing that measures 102 x 175 x 58 mm. The front holds a power switch and a USB connector for powering a USB device. A second USB power outlet can be found on the rear together with a standard power connector and an IEC mains connector. Internally the technical design is simple but decent. An encapsulated torodial transformer, a rectifier, two 4700 micro-fired capacitors and a voltage regulator, exactly as I described in Part 1 of this series. The unit comes without any cable but they can be ordered with the unit separately. The price is € 89. This is a very big power brick, measuring 128 x 76 x 223 mm. The IEC inlet is on one short side together with the power switch. On the opposite side you find a DC lead and a power lead. Internally you find a heap of components. The toroidal transformer is in the center with in between the transformer and the IEC inlet two PCBs holding a fuse, filter components and switches that make the unit switchable between mains voltages ranging from 100 volts AC to 240 volts AC. On the other side of the transformer there is a PCB that does the AC to DC conversion using a discreetly built rectifier comprising of four diodes, a voltage regulator on a cooling profile with nearby the switch for 5, 5.5 and 6 volts and six 4700 micro-fired capacitors. A power lead plus some smaller components are also found there. The output cord is connected directly to the print. The other side of that cord ends in a small plastic box called the split current unit. This is not only one more filter, it also buffers the power to be able to provide power quickly to the audio electronics. The output cord of the split current unit ends in a special connector that has to be terminated by one of the supplied end tips to fit the device you want to power. That tip fits relatively loosely so you better use a heat shrink tubing to fixate it. If you, like me, frequently change from equipment, quality gaffer tape is a perfect solution too. There are six versions, each covering two or three voltages with the exception of 24 volts model that only has one output voltage. At 270 euros this really is a high end linear power supply. Let me again shortly explain how to connect the power directly to the DAC board. Go to an electronic shop, brick wall or virtual and order a print header that fits the two holes. Mine was by Veloman, it has 2.54 mm spacing to fit the holes in the print. You might at the same time order a female connector with wires. I paid 15 cents for the connector and 60 cents for the cord plus female connector. Postage costed me more. Simply solder the connector as shown, the plus 5 volts need to be connected to the pole closest to the GPIO bus, the return on the other pole. Now mount the board to the Raspberry Pi and forget your old power supply. Just connect the better power supply to the connector you just soldered. I have soldered the wires to a standard power inlet and mounted that on the housing for convenience. Again, you no longer use the standard power supply, only the new power supply connected to the DAC board. You could use a separate power supply for the Pi and for the DAC by bending or cutting away the two pins on the GPIO connector that form the power connection between the DAC and the Pi but I personally don't think this is necessary. I've listened to a wide selection of music but the differences between the power supplies appeared easily describable using Man in the Long Black Code by Bob Dylan from the album Oh Mercy released in 89. It starts with chimes and a steel string guitar. Those chimes, although relatively low in level, appear to be not the easiest of signals to reproduce, improving as the power supply got more expensive. I started of course with the stontronics directly connected to the Pi and not to the DAC board as mentioned. The chimes sounded distorted and grainy and rather unpleasant. Then improved clearly when switching to the iFi iPower supply and improved in two smaller steps when switching to the audiophonics and the sBooster consequently. The next remarkable sound comes from the mouth harp, that with the stontronics sounded like anything but a mouth harp. With the iFi it became a mouth harp and got dynamically more appropriate although there was some unnatural colouring. The audiophonics improved this further but only when the sBooster was connected the mouth harp really found its place in the mix. About the same development can be found in the bass and in the stereo image. Using the stontronics power supply a stereo image was even fully absent. The most clear difference can be found in Dylan's voice, however. Using the stontronics it sounded if he got involved in a bar fight and lost some of his teeth. Since that's no proper behaviour for a Nobel Prize winner I assume it is to blame to the stontronics power supply. The iFi improves that a bit, just like the audiophonics while the sBooster gets it even further although still not optimal. This is where the limits of the DAC kicks in and that's nothing to be ashamed of since many separate DACs in the lower prize range don't manage either. As a reviewer you always hope for an inconsequent outcome of these kinds of reviews but that didn't happen here. Not very surprising the sBooster power supply wins by a car-sling and given its price it better. But what if you have a €500 stereo set? Will it be just as audible? Of course not. The difference between the stontronics standard power supply and the iFi will be though. Spending the €49 does clearly pay back especially if you are willing to do the suggested modification to connect the iFi directly to the DAC board. The audiophonics again when connected to the DAC board will be advisable in sets up to €2.000 or perhaps even €3.000 and the sBooster is by far the best in sets from €2.000 or perhaps even lower if you're critical. If you're in the market for a high-end power supply like the sBooster you could wait somewhat more for a review of other high-end power supplies that is in preparation. I am also working on a test using other equipment like the SOTM-SMS-200 and Sonora MicroRendu. Please don't ask me for a release date. It will be ready when it's ready. If you subscribe to this channel or follow me on Twitter, Facebook or Google+, you will see when it is published. If you have another question, please post it below this video but please don't ask me for buying advice. View my About Questions video to find out why. I have posted more information below this video and if you like this video please consider supporting the channel through Patreon and tell your friends on the web about it. I'm Hans Beekhuyzen, thank you for watching and see you in the next show or on theHBproject.com and whatever you do, enjoy the music.