The following comparisons to the HA-2SE+ were completed using a mix of high-impedance headphones including the Sennheiser HD660s 2, and the ZMF Headphones Atrium, (open-back version) as well as planars such as the Audeze MM-500.
The first in the HA-2* series was launched back in 2017 and I got my first demo of it in 2018 at the CanJam Singapore show. Our review of the HA-2SE was out later that year and it also won a 2018 Top Gear Award.
The HA-2SE is the true predecessor to the HA-2SE+. It uses virtually the same top-loaded tube configuration with 4 EL95/PL95 pentode power NOS tubes that are switchable from the rear panel depending on your preferred configuration.
The single input tubes on each do differ with the original unit using a Tung-Sol 12AU7W / 6189 and the HA-2SE+ using a JJ branded ECC81 or 12AT7 input tube which is a medium gain double triode design.
Both have excellent low microphonics performance though the Tung-sol has a much lower gain factor of 20 and higher current output compared to the ECC81’s stronger gain rating factor of about 60-70.
The Class A amplification output power is quite similar at 1W each constant via their respective impedance selector switches. Both offer the same impedance values ranging from 50Ω to 600Ω though the HA-2SE+ dial is much easier to access for quick adjustments on the front panel and the HA-2SE’s dial is hidden at the back.
The HA-2SE+ also offers a 3Vrms pre-out which the original version did not, instead offering 3 analog line-in options and a corresponding triple input switch option to the front.
The original HA-2SE is one of the most beautiful desktop tube amplifiers I have ever reviewed to this day. Even the new HA-2SE+ kind of takes a second slot behind this organic wood and leather retro-tones of its predecessor on aesthetics and eye candy alone.
However, functionality- and useability-wise the HA-2SE+ has some serious upgrades. Its new streamlined all-black metal housing should be more durable to extreme climates though personally, I have had no issues with the robustness of the HA-2SE in the last 5 years.
The HA-2SE+ also has more accessible features with all of the options on the front panel and is clearly labeled for easy use. It also has XLR inputs and PO options giving you more flexibility for specific connections though both are single-ended amplifiers.
The older version had a mix of front and rear dials, (impedance selector), meaning if you are on a tight rack space up against the wall it might be harder to reach. The recessed nature of the dials on the older HA-2SE means you kind of needed to be at head height to see the dial’s exact position.
The horizontal alignment of the tube sockets on the HA-2SE+ now has a lot more space around them for easier access. The older model had them bunched a lot closer making it harder to roll specific ones or clean around them.
One last final observation on the design is the feet. The original used sharp spikes mitigated by separate metal disks to steady the spikes and prevent potential surface damage. It made the unit quite tall as a result. The HA-2SE+’s integrated rubber-tipped pillars are much simpler, lower profile, and steadier on surfaces.
Testing with the Atrium and the HD660S2 you can tell right away there is a big difference in the performances of the original versus the HA-2SE+.
The latter is more expansive and holographic in its presentation with improved depth from stronger and fuller bass response and noticeably better headroom on the highs. The HA-2SE+ is also more refined tonally, with a better harmonic balance though still more to the warm and sweet side overall.
The HA-2SE sounds more compressed and less capable of filling out the Atrium’s very capable staging qualities. There is a more mid-centric and center image-biased performance from the older amplifier offering less instrumental separation and air as a result.
The original is as warm but also a bit more blunted in its note’s timbral balance lacking the same sparkle and very slight treble overtone more readily noticed in the HA-2SE+ that gives the new amplifier that superior refinement and clarity.
There is still the same perception of energy from the HA-2SE but combined with the blunted note definition and inferior separation it can sound hazier and less refined on busier passages.
That is something you want to avoid with the HD600S2’s more intimate soundstage. Things can get lost a little in the mix compared to the HA-2SE+ more precise placement with these headphones.
Auris Audio HA-2SF
The successor to the original, the HA-2SF was launched in 2021 with our review coming out around the same time. This was also a highly rated amplifier winning our 2021 Top Gear Award for Best Desktop Tube Amplifier.
Another Class A SET amplification design with pre-out capability but this time the tube configuration is a bit different from the HA-2SE+. The HA-2SF uses four JJ Electronics ECC99 9-pin double triode power tubes as opposed to the HA-2SE+ classic EL95/PL95 lineup and a single input JJ Electronics ECC82 tube.
The ECC82 is a 12AU7 medium gain pre-amplifying double triode design so again a much lower gain factor of around 20 compared to the 60-7o of the JJ ECC81 input tube used on the HA-2SE+. It will, however, deliver stronger current and potentially more headroom.
Given the HA-2SF is a more powerful single-ended design it would seem a logical choice of input tube characteristics for this amplifier. However, tonally it’s a bit different from the HA-2SE+’s ECC82 tube which is a little warmer in tone for me.
At 2W consistent across the impedance options, the HA-2SF amplification output does offer more headroom and power compared to the 1W consistent output of the HA-2SE+. It will be a more friendly match-up for dynamic headroom for harder-to-drive headphones.
Both of these amplifiers offer a 3Vrms pre-out on the rear allowing them to act as pre-amps in HiFi setups with a moderate high-/low gain stage output on the HA-2SF on the rear panel.
They also both share impedance selection options, however, the HA-2SF is a bit vaguer at 32Ω to 600Ω split into low, medium, and high which means more of a subjective adjustment based on your listening tests. The HA-2SE+ has clearer markers starting at 50Ω up to 600Ω.
I have much the same feeling about the HA-2SF aesthetics as my comparison of the HA-2SE to the HA-2SE+. The retro wood/leather and LED VU meters combination of the HA-2SF is just inspiring to my eye and one which makes me want to ensure everyone sees it in the listening room.
The black metal housing of the HA-2SE+ has its own charm but it is much more masculine so it has its own distinct appeal as a more traditional ‘HiFi look’. Granted, it is lower profile, however. There are some that felt the light show from the VU meters and under the tubes was a bit much on the HA-2SF.
The useability criticisms of the HA-2SF are much the same, perhaps more so than the HA-2SE when compared to the HA-2SE+.
The switch to the top of the panel for all the selector dials and volume control makes it very desktop-unfriendly if it’s higher than your line of site. The deep recess of the wood around the dials also attracts a lot of dust and the tighter tube physical spacing makes it more difficult to clean around without having to roll out the tubes.
You also have to consider that the HA-2SF is externally PSU-powered so it does teak up a bit more space than the HA-2SE+ whose PSU is now inside the main chassis.
Both amplifiers do come with 3-pin XLR inputs and outputs though they are single-ended circuits. I do actually prefer the switch of the HA-2SE+ compared to the plastic button on the front panel of the HA-2SF, it just feels more premium.
There are a few differences between these two amps but as to which one you will prefer it will come down to either tonal preferences or how inefficient your chosen headphones are.
For example, the HD660S2 is a much better pairing with the HA-2SE+ than the HA-2SF for my listening preferences.
Much of that comes down to the more neutral tone of the HA-2SF and how it reproduces the HD660S2 treble which can get a bit more dominant and harder-edged with the older amp.
The HA-2SE+ smoother sound relaxes that treble presence with leading edges more liquid or softer in tone. You still get plenty of sparkle but the harmonic balance is sweeter and more agreeable to my ear.
Also, the HA-2SE+ low end is also more voluptuous or fuller sounding on the lows of both the Atrium and the HD660S2 compared to the energetic punch and slam of the HA-2SF.
Now, with 2W consistent at every impedance level the HA-2SF will convey a bit more headroom and dynamic range with harder-to-drive planar headphones.
The HA-2SE+ really comes into its own with high-impedance headphones and more efficient planars. The synergy is excellent with the MM-500, more so than the HA-2SF which, again, can be a bit steelier and more neutral on the MM-500 highs.
However, once you move up to the likes of the Dan Clark Audio Stealth, the HA-2SF’s additional power does offer more headroom and a firmer bass response whereas the HA-2SE+ sounded a little too light on the lows for me on the same pairing.
Feliks Audio EUFORIA evo
The Feliks Audio EUFORIA evo was launched earlier this year and is the 3rd generation of their Euforia series of OTL headphones amplifiers. You can read our full review of the EUFORIA evo which was published earlier this year here.
Both amplifiers are single-ended, though the EUFORIA evo is technically a single-ended pure OTL or output-transformerless headphone tube amplifier as opposed to the HA-2SE+, which is a SET, (single-ended triode), design.
Typically, purists will reach for an OTL amp for high-impedance headphones with transformer stages seen as limiting the potential of their gear performance.
The tube configuration is very different between these two amplifiers. The EUFORA evo uses a matching set of PsVane CV181 MK2 “Gold” drivers combined with a pair of 6N13S (NOS) black-plated Svetlana “Winged C” branded power tubes.
The tube outlay on the EUFORIA evo costs significantly more than the four EL95/PL95 NOS power tubes and the single input JJ Electronics ECC82 used by the HA-2SE+. That can be a pro or a con depending on rolling plans as the cost outlay to upgrade on the EUFORIA evo will set you back medium triple-digit numbers.
The EUFORIA evo does not have the same approach to amplification output as the 1W consistent output of the HA-2SE+. It has no impedance selector options so its power output is on a curve. It can go higher at up to 1680mw into a 50Ω load but also lower at up to 280mW of SE output power with 20 dB of gain into a 300Ω load.
The output impedance of the evo is set at 65Ω so you get a good idea of the type of headphones this amplifier is best suited to. The HA-2SE+ is more flexible down to 50Ω but overall, my feeling is the HA-2SE+ matching is also going to be more high impedance optimized.
Both of these amps do offer pre-out capability though the evo offers an additional unusual crossfeed switch designed to target the bass response and central imaging for older wide stereo field recordings.
Although built with a similar monotone-colored aluminum housing, the EUFORIA evo is much smaller and lighter by 2kg compared to the HA-2SE+. It is a true desktop-sized unit but it does get a fair bit warmer than the HA-2SE+ so, make sure it is in a properly vented area.
The evo styling has a bit of a stylish accent on the front panel, not too dissimilar to the design language used on the flagship Envy with its oversized potentiometer dial and cutaway down the middle to allow for the connections.
The HA-2SE+ is a bit simpler, and more uniform in its design but very easy to access with legible bold labeling on the front plate. The power switch to the front of the HA-2SE+ is also more useful than the rear position on the Euforia Evo though an on/off label would have been ideal.
The evo lacks any of the impedance selection options but its crossfeed feature at the rear is an interesting coloration for old-time stereo recordings with an overly wide level of stereo separation that needs some solidity down the middle imaging.
Both units offer XLR outputs even though single-ended, however, the HA-2SE+ offers more inputs on the rear including 3-pin XLR inputs as well as dual RCA. Both of their pre-outs are dual RCA SE.
I tested 3 headphones between these two amps; the ZMF Headphones Atrium open, (300Ω), a classic AKG501, (120Ω), and a low impedance planar, the MM-500, (18Ω). Between the three I did have some preferences between each amplifier.
Overall, the EUFORIA evo is a more relaxed tuning with fuller warmer sub-bass that tends to present at a more languid pace combined with a creamier euphonic midrange and some excellent headroom. It can push things out deep, wide, and tall with the center image often more relaxed than forced.
It has that classic atmospheric but slightly diffuse tube soundstage with a stronger emphasis on richly textured notes with bass and vocal fullness coming to the fore. That did wonderfully well with the Atrium’s cavernous staging quality and its own liquid timbral tuning.
The HA-2SE+ is fairly smooth sounding also but it is not as voluptuous and creamy sounding as the evo. It has a busier-sounding mid-centric tuning combined with additional mid-bass punch energy.
Of the two it offers a shorter note decay giving a slightly stronger perception of clarity and speed but with less sub-bass presence and headroom.
This type of tuning combined with the 150Ω setting strongly suited the older K501 which tends to bias to the mids by default with less propensity for bass power and depth. By contrast, the K501 delivered a wide, deep, and tall image on the evo but with less of a focus on the mids.
The ability to drop to 50Ω also gave a more neutral and balanced central image with the MM-500 performance. However, at times, the evo sounded more expansive and deeper with the Audeze headphones.
Neither amplifier seemed to struggle to drive any of the chosen headphones with no noticeable distortion at moderate to above normal listening levels.
The Auris Audio HA-2SE+ is the perfect balance between the original’s charming tonal quality and the HA-2SF’s more aggressive but also more neutral tuning. It is beautifully refined and energetic with a smattering of welcome tube sweetness making it a very engaging SET headphone amplifier.
It pairs perfectly with just about any modern or classic voltage-demanding dynamic driver headphone but rarities like the 200Ω LCD-4 also perform surprisingly well. The classic multi-value impedance selector switch also gives you plenty of additional ‘flavoring’ to tweak the final output if you so wish.
Nothing is ever perfect in this world and I do think the new all-black metal housing will polarize some previous fans of the nostalgic retro-wood designs of the first two amplifiers.
You will have to weigh up the pros of improved durability and the more accessible controls of the new over the aesthetical charm of the old and see what is more appealing to you.
On performance alone, it really should be the newer HA-2SE+. This is a seductive-sounding upgrade on the original HA-2SE’s tuning and to be honest, it’s perfect timing with the recent renaissance of the high-impedance dynamic driver headphone exemplified by the likes of ZMF headphones and Focal.
Auris Audio HA-2SE+ Technical Specifications
Tubes: 1 x ECC81, 4 x PL95 (or EL95)
Tube Selection: Manual Switch
Input Sensitivity: 1 Vrms
Input Impedance: 470 k
Power Output: max 1W
Output Impedance: 50 | 150 | 300 | 600 Ω
Analog Inputs: 2 x RCA, 1 x XLR
Analog Outputs: 1 x 6.3 mm, 1 x XLR
SNR: 110 dB
Dimensions W x L x H : 310 x 360 x 195 mm / 12.20″ x 14.17″ x 7.67″