Spoiler: Click to show! I’m a 43 year old music and sound lover that changed my focus from speakers to headphones and IEM’s about five years ago. At that time I realized that it wasn’t realistic for me to have all the different setups that I wanted and still house a family of four children and a wife so my interest turned first to full sized headphones and later also IEM’s.



My preferences are towards full sized open headphones and I believe that also says something about what kind of sound signature I prefer (large soundstage in all directions, balanced and organic sound).



My music preferences are pretty much all over the place (only excluding classical music, jazz and really heavy metal). My all-time favorite band is Depeche Mode although I also listen to a lot of grunge/indie, singer/songwriter/acoustical stuff as well as the typical top 40 music.



I do not use EQ, ever.



I’m a sucker for value for money on most things in life Head-Fi related stuff is no exception.



Spoiler: Click to show! Mark Knopfler – Sailing to Philadelphia

Røyksopp (Feat.Susanne Sundfør) – Save Me

Ane Brun – These Days

Michael Jackson – Dirty Diana

Metallica – Die Die My Darling

The Peter Malick Group – Immigrant

Eva Cassidy – Songbird

Thomas Dybdahl – A Lovestory

Norah Jones – Don’t Know Why

Celldweller – Unshakeable

Jack Johnson – Better Together

Seinabo Sey – Younger (Kygo remix)

Dire Straits- So Far Away

Bjørk - Moon

Lupe Fiasco - Deliver

Morrissey – Earth Is the Loneliest Planet

The M-stage HPA-1 was purchased by me from an eBay seller about a year ago for $180 including a class A biased OPA627 op amp.The HPA-1 was the first generation in the M-stage series and have since then been followed by the HPA-2 and the quite recently released HPA-3. The HPA-1 was released back in 2010 but I still think that it offers enough interesting features to be worthy of a review in 2016.The HPA-1 came with one version without built in DAC (the one that I’ve got) and one with built in DAC. Both were available in black and silver so a total of four different offerings were available. To my understanding the original version with USB is no long available (but generation 2 and 3 is) while the pure amplifier version is.The HPA-1 is still available from several sellers and here’s a link to the Amazon listing of it:http://www.amazon.com/Matrix-m-stage-HPA-Headphone-Amplifier/dp/B0056ER22EI’m not in any way affiliated with Matrix.Matrix Electronic Technology Co. Ltd., located in Xi'an Economic and Technological Development Zone, is a high-tech enterprise that dedicates to the R&D, manufacture, marketing and sales of high-fidelity digital audio products. The company has its own digital audio brand; meanwhile, it also collaborates with a number of domestic and foreign companies on OEM and ODM business.Homepage:http://www.matrix-digi.com/en/index.htmlThe Matrix M-stage HPA-1 is a solid state headphone amplifier.The HPA-1 is literally built as a tank. It’s made of metal and feels very reliable both in outer- and inner- design. It really feels like a non-nonsense product built to last for a long time.The physical design of the HPA-1 (long in depth and short in width) is a not typical one and this may be a problem for people preferring to stack their gear.The volume knob does also feel very solid and has a perfect amount of resistance when being moved to raise or lower the volume.The HPA-1 offers two RCA inputs where you connect your sources and one RCA output for its pre-amp function. It also has a 6.3 mm jack to connect the headphones to.To continue it also offers a switch to choose which of the line in sources to listen to and underneath it also has gain switches. The gain switch can be put to four different options: 0, 10, 18 and 20dB. I really like to have four gain options to choose from. This was the reason for me choosing the HPA-1 over the newer HPA-2 when I made my purchase. Finally there’s also an On/Off switch which, unfortunately, is placed on the back and makes it a bit hard to reach when placed in a rack.· Output: discrete· Gain Switchable· Frequency Response: 10 Hz (-0.3dB) ~ 35kHz (-1dB)· Signal to Noise Ratio: >95dB (0dB)· Distortion: <0.001% (6 mW/300 Ohms)· Input Impedance: 47 kOhms· Output Impedance: Line-out 60 Ohms, Phone-out 5 Ohms· Output Power: 200 mW/300 Ohms, 400 mW/60 Ohms· Power Support: AC 220-240V/100-120V· Front Panel Color: Black/Silver· Weight: 2 kg· Device Dimension: 280 x 110 x 42mmI’ve used the M-stage on and off for the last year and it have played for well over 100 hours.I’ve fed it from my Advance Acoustic MDA503, the GO720 and the CEntrance DACport Slim and it has worked very well in all combinations.I’ve got to be honest and admit that I find it pretty difficult to describe the sound from an amplifier. To me the sound of headphones/IEM’s is more easy to describe than that of amplifiers and DAC’s. Because of this I’ll do a brief description of the overall sound from the HPA-1 and then compare it to a couple of other amplifiers to highlight the difference and similarities to them.The first thing that I noticed when I started to listen to the M-stage was the black background. It was simply on another level than I’ve ever heard before. It sounds so calm and with great authority to everything it does. I don’t feel that it does not highlight any particular frequencies but the overall sound is full and slightly on the warm side. Although it doesn’t sound very vivid it doesn’t strike me as particularly laid back either, neutral with a warm tone would probably be the best way I can describe it. The extension in both ends is very good and I don’t think that anything is missing. Soundstage feels natural and separation is very good. While some amplifiers with wide soundstage can tend to sound slightly diffuse (combined with some headphones) I don’t find this to be the case at all with the HPA-1 and it’s very easy to hear the position of each instrument. I’d characterize the overall signature as full, distinct, slightly warm and with an excellent timbre to it.The M-stage uses one dual op amp that’s mounted in a DIP8 socket and is very easily user replaceable. I general I find op amp changes to be quite subtle, especially when a/b testing with short listening sessions. I find that long time usage makes it easier to say at least which sound you prefer and which may cause more fatigue or other wanted/unwanted characteristics from the different op amps. Still I’d consider op amp changes fine tuning kind of in the same way as with tube changes. In short the Matrix M-stage will always sound like the Matrix M-stage but smaller adjustments are possible. I’d also like to say that there are no “better” or “worse” op amps in my opinion but there may be differences in synergy with the rest of your system and of course also in what preferences one have.As I’ve already mentioned my HPA-1 came with the OPA627 pre-installed. Lately I’ve acquired a MUSES8820 op amp and Burson have been so kind to send me a sample of their Dual Supreme Sound (SS) V5 op amp for my shoot out. Big thanks to Dennis at Burson Audio for the support of my little project and for putting up with all of my questions.For those interested in reading more about the latest generation of the Burson op amps (V5) here’s the link to their site with more information:I've also posted a review for the Burson Audio SS V5 with more detailed information about it. Those who's interested can find it here:http://www.head-fi.org/products/burson-audio-supreme-sound-opamp-v5/reviews/15046With the OPA627 installed the warmth in the HPA-1 is easily noticeable but clarity and details are still in place. Focus on each instrument is excellent and the OPA 627 is the most intimate sounding among those tested here.Full bodied, focused and warm is keywords for this op amp.With the SS V5 the black background of the HPA-1 is even more noticeable. There’s also more air to the presentation and the stage feels wider while still keeping the great positioning of each instrument. The more airy presentation also makes it feel less warm if that makes sense. The V5 has great extension in both ends.Rich, detailed and airy is keywords for this op amp.The MUSES8820 sits nicely in between the OPA 627 and SS V5 when it comes to warmth and soundstage. It has good extensions in both ends and is quite neutral.Neutral and yet very musical is keywords for this op amp.I’ve also made a short breakdown of the characteristic of the three op amps I’ve compared:627 > 8820 > V5V5 > 627 = 8820V5 > 8820 > 627V5 > 8820 > 627V5 > 8820 > 627V5 > 8820 = 627Once again these differences are not big but it’s how I hear them with my ears in my system. That being said it’s no doubt that I prefer the Burson offering over the others for long term listening.The output impedance of the headphone out on the HPA-1 is rated to 5 ohms. This means that it may not be the ideal pairing with very easy to drive headphones and IEM’s. In theory it should be paired with headphones that has an impedance of 40Ohms or greater to perform its best.The HPA-1 has plenty of power to drive all my full sized headphones, even my modded Fostex T50RP’s, which are the most demanding pairs I’ve got in terms of power, get more than enough power from the 10dB gain setting. The official power rating of the M-stage is 400 mW at 60 Ohms and 200 mW at 300Ohms so it should be enough for most headphones.The combination of the HPA-1 and the Q’s are a match made in heaven in my opinion. The slight warmth and power from the M-stage really bring out the best from the Q’s. Bass is as impactful as I’ve ever heard with them and the overall presentation is very enjoyable. Also the great positioning and separation of the M-stage seem to work very well with the Q’s which can be a bit diffused with some sources in my opinion.Although the Grado’s only have an impedance of 32Ohms I find them to sound excellent combined with the M-stage. The slight warmth combined with the full and calm presentation seems to pair very well with the lively nature of the Grado’s giving them a very pleasant and enjoyable overall sound.Although the X2’s certainly doesn’t sound bad with the M-stage it’s the only headphone that I enjoy even more with the Little Dot I+. I don’t know if it’s the 30Ohms impedance of the X2’s or the full and warm nature of the HPA-1 that’s to blame but on some recordings the bass get slightly too much for my preference. After spending a lot of time (and money) on different tubes and op amps for the LD I+ to make them perfect for the X2’s I’ve settled on a combination of Siemens 6AK5W tubes and the MUSES8820 op amp that really bring the X2’s to the next level for me. The midrange is more forward and mid-bass slightly reduced compared to the HPA-1.Please note that the comments in the comparison section are not in absolute terms but in comparison between subject A and B. This means (as an example) that if subject A is found to be brighter than subject B it does not necessarily mean that subject A is bright sounding in absolute terms. I hope this makes sense.I this comparison both amplifiers were fed by the Advance Acoustic MDA503 DAC equipped with Ei NOS tubes in the output stage. I’ve been listening through my Philips Fidelio X2’s.I used a simple Android app to volume match the amplifiers so although maybe not perfectly scientifically the result should still be pretty correct.I used the M-stage with the Burson SS V5 installed when doing this section.The LD I+ ($140) is smaller than the HPA-1 and has a built in power supply solution just like the HPA-1.As already mentioned I’ve settled on a Siemens/MUSES combo of tubes and op amp for the LD I+ and that’s what I’ve used it with in this comparison as well.Being a tube/solid state hybrid the LD I+ introduce some noise with easy to drive IEM’s that makes it not match the HPA-1 in the level of black background. Compared to the M-stage the LD I+ have a more forward midrange and a very slightly less warm sound with a more lively presentation. The M-stage on the other hand feels more even across the frequencies and also slightly fuller and with more authority to the way it sounds.The HPA-1 offers a bit higher power output (200 mW for the HPA-1 vs 150mW for the LD I+ at 300Ohms). The LD I+ also offers a gain switch for 3.25 or 6.5 dB compared to the HPA-1’s four different settings (0, 10, 18 and 20dB). Unfortunately the output impedance of the LD I+ seem to be unknown except for the fact that it’s said to be made for low impedance headphones. The LD I+ has one pair of RCA inputs while the HPA-1 offers two and one set of outputs for pre-amp function.The Magni ($99) is much smaller than the HPA-1 and has a power supply solution that requires a wall wart in contrast to the built in power supply on the HPA-1.Compare to the M-stage the Magni has an overall slightly thinner but also cleaner presentation. While the M-stage is slightly warmer than what I’d consider to be neutral the Magni is what I’d describe as spot on neutral. The result is a slightly more full sound most easily noticeable with male vocals and also more distinct character on the M-stage. The Magni can tend to sound a bit shouty (in comparison) with some music (Michael Jackson – Dirty Diana is a good example of this). They both offer similar great sense of space, separation and bass depth. The M-stage does have a more black background.The Magni also offers a slightly higher power output (260mW at 300Ohms compared to 200mW for the HPA-1) but has no gain switch and its fixed gain is very high (making it more difficult to use with easy to drive IEM’s). The Magni has a very low output impedance (less than 0.1 Ohms) compared to the slightly high 5 Ohms for the HPA-1. The Magni offers a pair of RCA inputs while the HPA-1 offers two and one set of outputs for pre-amp function.The Matrix M-stage HPA-1 may not be the latest addition to the amplifier market but it may very well be one of the best values with current prices.The combination of four different gain options, pre amp function, two set of RCA inputs, easily user switchable op amps for fine tuning the sound and an excellent overall performance makes it a great option as long as you can live with an output impedance of 5Ohms.In combination with the Burson SS V5 op amp it has become my favorite amplifier, especially when driving headphones that need a good amount of power to perform their best.This has been a project over several weeks and I've enjoyed every minute of it. Hopefully you've enjoyed reading it as well