LOXJIE P20 Full Balance Tube Amplifier Headphone Power Amplifier (Black)

Some on the web have recently been pushing the Loxjie P-20 hybrid headphone amp as the new audio "Wunderkind" of the audio world at only $99. However, there are some gotcha's ...For starters, the included 1.6A switching power supply seemed to create a buzzing sound on all the audio when I first used this amp. I fixed this by replacing it with a dependable, beefy 3A linear power supply in its place. I suspect the cheap Chinese-made switching power supply is not really supplying enough amperage for this amp. Try using a well made 3 amp power supply if you can find one. Next, hooking it directly to the headphone output of my iPad Mini 4 resulted in loud, random crackling sounds. WTF? OK, so I moved to using it with my JDS Labs ODAC DAC hooked to my Apple PowerMac desktop and the loud crackling stopped. But, wait, what is going on with the highs? They sounded strident and distorted and not in a good tube way. Bass seemed lacking, too. OK, so I removed the stock 6N3J "military grade" Chinese tubes and replaced them with a pair of closely matched Riverstone "platinum grade" 6N3P-E (Russian) tubes. Ah, much better. More defined bass and the strident, distorted highs went away.I did all the initial testing with the unbalanced audio-in and the unbalanced audio-out jacks. Yeah, this headphone amp is suppose to be audio nirvana using the XLR balanced jacks but it should also perform at least with decent sound on the far more common unbalanced jacks. I've got a SMSL SU-8 DAC on order with XLR balanced audio outputs that I'll later try along with some HD650 balanced headphones but not for now. One thing I did seem to notice is that this amp seems to like high impedance headphones even in the lower powered unbalanced headphone mode. My warm sounding Fidelio X2 headphones (30 ohms) sounded OK on this unit. However, switching to 250 ohm Beyerdynamic DT990 Pro headphones sounded much better even in unbalanced mode. There was good control of the bass and the soundscape was nicely defined. There also seems to be something special going on with the imaging in the mid-range on this headphone amp. Not sure what it is and it seems to be far more present on the high impedance headphones than those of lower impedance but I like it. A little bit of the so called Loxjie P-20 "magic", I suppose.If you order one then you must plan on the possibility of needed to work with it to get it to sound at its best. Your "out-of-box" experience may be frustrating at first. For now, I'm giving the P-20 only 4-stars due to the initial problems that shouldn't be happening "out-of-box". Construction quality is good but not fantastic. I'm bothered by the volume control which is loose and wiggles around. It needs to be better stabilized. Unit could also use more vents to help with the heat it generates. If later testing with the balanced HD650 headphones along with a balanced XLR output DAC improve things I might up the rating some but the initial frustration I had with this amp only rates it 4-stars for now. Oh, and Loxjie absolutely needs to put an Off/On switch on this thing. That's right, there is none. It turns on as soon as the power plug is inserted. You can push in the wiggly front knob to turn in on/off but I would much prefer to see a rocker switch on the back for power. Given the flakey, under amp'ed switching power supply they include, I would NOT want to leave this thing running 24x7 due to heat and fire concerns with this cheap power supply.Finally, don't expect this unit to produce full blown "tooobe sound". I have an inexpensive Chinese Qinpu Q-2 from several years back that I bought for the same price that does much better in this regard. This is not the headphone amp you want for creating lucious tube sound. It's much closer to solid state sound. Not a bad thing but just make sure you know what you are getting. And realize that for Loxjie to price this nice sounding headphone amp under $100 they had to cut some corners. They included an awful, cheaply made Chinese switching power supply which just barely supplies the required power. Upgrade it to a good power supply that is rated to at least 3A. Some users have mentioned good results using the 5A Jameco Reliapro KPL-060F switching supply ($16). Second, get rid of the awful 6N3J "military grade" Chinese tubes. Those are cheap tubes that can easily be found for around $6 each. They are cheap for a reason. Substitute something like the Russian 6N3P-E that can be supplied in a closely matched pair for about $30 for the whole pair. After those two critical mods you'll have a great sounding headphone amp that handles high impedance headphones very well for not a lot of money.UPDATE 04/20/19 -- Nix the idea of using the Jameco Reliapro KPL-060F. One poster mentioned it so I ordered one to try out on the P20. No go. It has a smaller 2.1mm inner hole that won't fit on this unit. You need a power plug that has a beefier 2.5mm size inner hole (5.5mm cylinder on the outside). I've got a MEAN WELL GS90A12-P1M 12V 6.6A regulated switching power supply ($32) that is overkill for this thing but it should work and fit the power port on the P20. It looks to have the required 2.5 x 5.5 mm plug size to do the job.UPDATE 04/22/19 -- The Loxjie P20 runs a bit hot after being on for a while so I looked for quiet cooling solution. Any fan to pull out heat has to be pretty small because the top vent is small. Ordered the "Easycargo 2-Pack 40mm USB Fan, USB Mini-Fan 4010 5V with Multi Speed Controller". Both fans go on the same single USb cable + Speed controller connection. Each of these small 40mm fans can pull about 6 CFM at full speed which isn't very much. However, I double-stacked them on top of each other (be aware of the air flow directions) so that they would pull heat out like an elongated chimney stack from the top Loxjie vent with around 12 CFM of combined fan pulling power and got some excellent cooling results. I don't think a single 40mm fan by itself would give enough cooling power. With this setup of stacked 40mm cooling fans the P20 is now running much cooler and the fans are reasonable quiet, being so small.UPDATE 04/23/19 -- Finally received the ordered MEAN WELL GS90A12-P1M 12V 6.6A regulated power supply from Amazon. The power plug fits beautifully and is the correct 5.5x2.5 mm size. At over 6 A it has plenty of power and the build quality of ths PS is very good. Testing shows it to put out a very steady 12.3V output with no variance. Have been using an older/cheaper balanced XLR output DAC -- Behringer UltraMatch SRC2496 -- while awaiting the arrival of a more modern SMSL SU-8 balanced XLR output DAC. Putting a pair of XLR balanced Sennheiser HD650 headphones on this little jewel is resulting in incredibly detailed but non-fatiguing sound. Best I've ever heard from a headphone setup. Therefore, I'm raising my rating to 5-stars because with balanced XLR inputs/outputs it sounds so incredibly good. Just be sure to replaced the horrid Chinese power supply and the enclosed Chinese "military grade" 6N3J tubes that come with it. Oh, and please Loxjie.... please put an on/off rocker switch on the back.

First off, the Loxjie P20 is built like a mini tank. Moreover, it's finished beautifully. In this Hi-Fi enthusiast's opinion, it's worth every penny Loxjie is charging for it. I say this because the P20 also offers a vacuum tube input stage with quality components such as WIMA caps, for a total as shipped price of $89.99 (with Amazon $10 coupon). This makes the P20 the lowest priced fully balanced headphone amplifier on the market at the present time.I've done my subjective listening with upgraded Riverstone "platinum grade" 6N3P-E tubes, which definitely do improve the sound of the P20. All of my observations regarding the P20 pertain to these upgraded tubes.Unlike some other P20 users, I have not experienced the buzzing sensation in the power supply, which may be caused bwy the PS being placed too close to a computer monitor. However, this is just speculation.Based on owning other headphone amp's in this price range including the Schiit Magni 3, JDS Labs Atom and Monoprice Monolith Liquid Spark designed by Alex Cavalli (all of which set the bar in this price range), in balanced mode the Loxjie more than holds its own against this competition and is constructed more solidly than the other three amplifiers.Each of the aforementioned amp's has its own unique sonic signature and does what it does quite well. And while the Magni 3 has been around for over a year, the Loxjie P20, Cavalli Liquid Spark and JDS Labs Atom have only been on the market for the past few months, yet are already receiving accolades for their high value to performance ratio.These amplifiers have also redefined performance in the under $100 headphone amplifier market. What they accomplish sonically, is better than what most headphone amplifiers five to ten times the price were able to accomplish less than a decade ago.This is truly impressive.As for summing up the P20, based on listening to it for the past few weeks, I'd have to say don't waste your time using this amplifier in unbalanced mode. It just does not have enough power unless you are using a low impedance headphone.However, in balanced mode the P20 becomes a different animal altogether. It has plenty of power to run high impedance headphones like my Sennheiser HD 650 (300 ohm MassDrop HD 6XX version) and HD-600's, as well as my AKG K240 Sextetts (600 Ohm), and has a refined sound (even with its stock tubes) that subjectively rivals amplifiers costing three to four times the price.I have also been using the P20 successfully with several different lower impedance headphones including the Meze Audio 73 Classics (32 ohms), Hifiman HE4XX (32 ohms), Audioquest Nighthawk Carbon (25 ohms), Fostex T50RP MK3 (50 ohms), NAD HP50 VISO (28 ohms), Grado SR-60s (32 ohms), Koss KSC 75's (60 ohms), Superlux HD681 EVO's (32 ohms), and Sharkk Bravo (40 ohms).As previously stated, I've also tried the P20 with some higher impedance headphones including the Sennheiser HD650 (Massdrop HD6XX version), Sennheiser HD-600, and AKG K240 Sextett.I find that in fully balanced mode the P20 works very well with each of these headphones. Moreover, in balanced mode the P20 has no trouble driving my Sennheiser HD6XX or HD600 (300 ohms) and even more surprising, it successfully drives my highly inefficient AKG K240 Sextetts (600 ohms) with headroom to spare.This is very impressive for a fully balanced headphone amplifier costing under $100.Most importantly, when used in fully balanced mode, the P20 scales very nicely with better sources, and is very involving to listen to.I really am impressed with the sound quality of this well constructed little headphone amplifier.As I stated earlier, in single ended mode the P20 sounds nice enough with efficient headphones (16 ohms - 63 ohms), however, it simply does not have enough grunt to power higher impedance headphones through its single ended inputs and outputs. It ends up sounding anemic and ultimately disappointing.So if you are going to buy this amplifier, prepare to use it in fully balanced mode and you'll be amazed at how capable the P20 is.And, moreover, what a great value it is.I'd also like to see Loxjie offer a fully balanced DAC for under $200 that matches the P20, since it will (along with SMSL's SU-8 {The latest version} and SH-8 balanced DAC and headphone amplifier) set a new standard for balanced headphone electronics in this price range.If the P20 turns out to be reliable, it will represent one of the best values in headphone amplifiers on the market.Thus far, highly recommended!