The HPA-5000 is an Output Transformer-Less (OTL) and Output Capacitor-Less (OCL) headphone amplifier. While there are plenty of OTL amplifiers out there to choose from, there are almost no OCL amplifiers on the market. Without using any output transformers or capacitors in the circuit, the headphones are pretty much driven by the vacuum tubes alone, which provides the smooth and organic tube sound many of us enjoy. The HPA-5000 uses eight tubes in total: Two 6AN8, two E180CC, and four 7233 tubes. The unit I listened to came loaded with Westinghouse 6AN8, Mullard E180CC, and GE 7233 tubes. Additionally, each tube rests on Allnic’s patented “Absorb GEL” vibration damping tube sockets; these are specially designed to reduce vibrations, noise, and micro-phonics. To protect the tubes, your hands, and the sockets, each tube is enclosed in a tube chimney (that opens with an Allen key) and a cool looking tube extractor is included.
The build quality of this amplifier is incredible and on par with other products in this price range. The lightly brushed aluminum finish is amongst the best I’ve seen and it is clear that there is a lot of attention to detail. Despite not being very big, the HPA-5000 weighs about 20 pounds. The two single-ended RCA inputs in the back are selected by pressing a small button and volume is controlled by a 41 stepped attenuator designed and built by Allnic. The amp even has two tube bias meters that can be adjusted with a small screwdriver.
The Allnic HPA-5000 has a gain of +28dB and can output a maximum of 5 watts into 50 ohms. The HPA-5000 is designed for driving low impedance headphones between 30-50 ohms. Simply put, it has enough power for pretty much any headphone on the market including the mighty HE-6, which I did most of my listening with.
I first heard the Allnic HPA-5000 last year at a headphone meet in Chicago. At the meet, I was able to use a pair of HiFiMan HE-500 and Grado RS1i to audition the amp. My listening time was brief, but I immediately noticed that this was a special amplifier. The pairing with the HE-500 was incredible, simply incredible. I fell in love immediately. The sound was very euphonic, warm, and romantic, more than most tube amps; yet the sound was clean and focused. Everything was in perfect balance. The HE-500 had excellent synergy with the HPA-5000, so much so that I actually preferred the combination over the more expensive Stax and Cavalli electrostatic setups that were also present at the meet. The music was sweet, seductive, and enveloping. You could listen for hours! The Grado RS1i pairing was excellent as well, driving them to their full potential and displaying similar qualities as the HiFiMan. The Allnic certainly left an impression on me that day and I thought about it for quite some time.
This summer, I was able to listen to the HPA-5000 again at the meet; this time with my pair of Fostex TH-900, a pair of LCD-3, and a pair of AKG K701. All headphones paired great with the HPA-5000 and I was blown away just like I was last year.
A few months later, I got a chance to listen to the HPA-5000 at home. Seeing how excellent the amp paired with the HE-500 and how effortlessly it drove every headphone I threw at it, I decided to give it a challenge, the notoriously difficult to drive HE-6!
For my listening, I used the HiFiMan HE-6 planar magnetic headphones. My source was lossless music files from my computer fed to my Mytek Stereo192 DSD DAC. I used Audioquest King Cobra RCA interconnects as well as Audioquest Power and USB Cables. The Allnic HPA-5000 was using the stock tubes (Westinghouse 6AN8, Mullard E180CC, and GE 7233). Music choices varied and included just about everything.
At first, I wasn’t really expecting the Allnic HPA-5000 to perform that well with the HiFiMan HE-6. The HE-6’s are very hard to drive headphones that require gobs of power for them to sound their best. When properly driven, they are one of the best headphones money can buy. However, an underpowered HE-6 can be quite dull. The soundstage collapses and becomes narrow, the midrange recesses, and the treble becomes grainy with a slight shrill. Most headphone amplifiers on the market, even expensive ones, fail to do the HE-6 any justice. Even if they have enough power, I can usually tell if the amp is struggling; it will feel as if something is missing and at louder volumes you might get clipping or distortion. Because of this, many people believe that a speaker amp is an absolute must for the HE-6. I was extremely surprised to find out that the Allnic HPA-5000 had none of these issues with the HE-6.
Though the Allnic can only output 5 watts into the HE-6, it felt more like 10 watts. The power on tap is more than enough for even the quietest of classical recordings. The stepped attenuator is also excellent, free of any annoying pops or click. The gain is well spaced out and I was always able to get the right volume I needed.
Dynamics are lifelike and natural, nothing sounding forced or compressed, even on poorer recordings and with newer pop and rock songs where it is very noticeable. There was also a connectedness and flow to the music; a liquidity of sorts that I only ever hear in the very best of amplifiers. It was never too fast, or too relaxed, it was just right. This helped make the HE-6 sound better than ever before and it was dynamic and fast enough for any genre of music. The tonally is close to perfection, there is absolutely no brightness, fatigue, or roughness to be found in the treble. Even at louder volumes, the sound was completely devoid of any grain or unnaturalness. The tone was always warm yet never overdone with lushness or thickness. The HPA-5000 maintains a good amount of neutrality and never sounds “colored” or “veiled” in any way.
The soundstage is well rounded, never too big or too small, it was just right. Instrument placement is excellent. Music through this amp is almost 3D-like with top level layering and imaging. There were tons of spatial cues to be found in every recording. Simply put, the clarity, vivid soundscape, and dynamics of the HPA-5000 create a coherency that not many amps can pull off. The feeling of realism is conveyed thoroughly; everything is alive. The treble – open, airy, extended, and grain free – adds to this effect.
The midrange on the HPA-5000 is clean. It is neutral for the most part with a hint of crispy forwardness, which helps produce a clear and focused sound. Along with the midrange was a clean treble that is never fatiguing but is forgiving, yet with no loss of detail. Because of this, I really enjoyed rock music while listening to this amp. Foreigner’s album 4 and Avenged Sevenfold’s Hail to the King were both great to listen to with the HE-6 and HPA-5000 pairing. Acoustic albums like Light’s Siberia also came alive; you can hear everything in the midrange – every detail, every nuance – and the emotion in her voice can be felt in every song.
When properly driven, the HE-6’s are known for having deep, tight bass as well as producing a clean decay and transparency… lots of it. I was happy to find out that the Allnic HPA-5000 and HE-6 combination delivered in this regard. The bass had plenty of body and texture, without being overblown, and the extension is fantastic with good slam. Overall, it was the tight visceral bass I was looking for. La Caina’s Vue Mer album sounded better than ever, the bass on many of the tracks is deep with lots of detail, most of which is veiled on lesser setups. Heavy bass recordings were easy for the HPA-5000 as well; there was no distortion at any volume and even the lowest frequencies were well reproduced.
“The Entity (SlaFF Remix)” by Substep Infrabass is one of the hardest tracks for headphones to properly reproduce. There is a deep 20-30Hz rumble that gets deeper as the track progresses and riding along with it is a constant mid-bass beat. The HE-6 is one of the few headphones that can reproduce it as well as a speaker and subwoofer system can (well, almost). However, it needs plenty of power and clipping typically occurs at louder volumes. With the Allnic HPA-5000 at its maximum volume of 5 o’clock, there was no distortion and it was as loud as I could listen. The Allnic HPA-5000 produces excellent bass, amongst the best I’ve heard from any tube amp.
Like the HE-500, the HE-6 pairs wonderfully with the HPA-5000. What really impressed me was electronic music like vocal trance and house. Armin Van Buuren’s Intense album particularly impressed me with tracks featuring Emma Hewitt & NERVO. Voices were always soft and rounded, and well balanced with the midrange. There was pleasant ambience to the sound, one full of air and silky smooth treble, complimented by the naturalness of the amp. The bass was enjoyable as well – tight, fast, and punchy. The HPA-5000 is incredibly musical and I listened to basically every genre with this amp and loved every minute of it.
I have two other amplifiers I use to drive the HE-6: The Woo Audio 5 and the Headamp GSX MK2. Both are considered to be top-of-the-line products, one offering beautiful 300B tube euphony and the other providing absolute wire-with-gain neutrality. Both are my reference amps of choice when reviewing headphones. The Woo Audio 5 is the more direct competitor to the HPA-5000, offering up to 9 watts of amplification. The 300B tubes make the WA5 more rounded and open sounding than the Allnic. The treble extends further, the midrange is more laid back, and with slightly more bloom to the bass. All in all, a different kind of tube sound. The WA5 is also warm like the Allnic, but everything seems more open and spaced out, giving a completely different sound signature. Transparency, speed, and detail are as good as the HPA-5000, but the differences are very small to notice. The WA5 also has more volume for the HE-6 to play with. However, I feel that the treble can still have a tiny bit of sizzle on poor recordings with the WA5. The Allnic is more forgiving and seems to have a more forward midrange, which gives it better synergy with the HE-6. The WA5 is close to perfect with the HE-6, and the HPA-5000 takes it to the next level, it’s just a little sweeter and more romantic.
The Headamp GSX MK2 has less power than the WA5, it can deliver about 5-6 watts into the HE-6, roughly the same as the HPA-5000. The GSX however, seems to struggle with the HE-6. The power seems to be barely enough, although the volume range is similar to the Allnic. The difference is that the GSX MK2 sounds strained with the HE-6, the treble can have a lot of sizzle at higher volumes and at its limit, it will clip and distort. The midrange is also somewhat recessed, as if the GSX MK2 doesn’t have full control of the HE-6’s drivers to really bring it out. Overall, the sound of the GSX MK2 is acceptable, with tons of detail – slightly more than the Allnic or WA5 – and the bass, at normal volumes, sounds powerful, deep, punchy, and tight. The GSX is also extremely transparent, offering a very clean window into the music and quick, almost liquid smooth transients. With less demanding headphones, all three amplifiers offer top level performance and one would have to audition them all to decide which best suits their preferences.
Other amplifiers that compete with the HPA-5000 include the Eddie Current Balancing Act, the Cavalli Liquid Gold, the ALO Audio Studio Six, the Apex Teton, and even the Ray Samuel’s Dark Star. Though my listening time with many of those amps has been brief, none have blown me away on the first listen like the HPA-5000 did.
Overall, the HiFiMan HE-6 and Allnic HPA-5000 paired wonderfully. I experienced the beautiful euphonic midrange that only tubes can provide, along with natural life-like dynamics, silky smooth treble, and deep tight bass. Even after hundreds of songs and countless hours of listening, I continued to melt away into the music itself. I just never get tired of the sound. The Allnic HPA-5000 is one of the best headphone amps I have ever heard, period. Just about every low impedance headphone available is driven to its full potential and there is little room for improvement; it’s that close to perfection.