RE・LEAF E5 studio: Current Drive Endgame?

Introduction

It’s been about two years since I discovered the world of current drive amps and their wonderful synergy with the Sennheiser HD800S.

My first current drive amp was the Bakoon HPA-01M (here’s a link to my article on it, comparing it to the Pathos Aurium), a portable, battery powered amplifier with both current and voltage outputs.
After a couple of months I managed to find and buy its big brother: the HPA-21, which was a definite improvement in technicalities, with a more refined tuning and presentation.

While I was doing all of that, in the back of my mind I was already planning for my next upgrade: a Re/Leaf current drive amp: a relatively small and very niche (at least in the west) manufacturer from Japan who focuses almost exclusively on current drive amps: the E3 hybrid dC, the E5 studio and the crazy expensive E1R DAC/AMP. At the time I was aware of them because of a forum member who had two E3 hybrid dCs in a dual mono configuration and he really liked them with certain headphones, like the HD800S.

The E3 was definitely out of budget for me, even if I managed to find one used. It also wouldn’t have made much sense for me to get one since it also has a voltage drive circuit that I wouldn’t really use, and if I understood correctly, its current drive circuit is the same used in the E5, which, while not being cheap (2-2.5k euros imported), was…actually something that I could afford relatively soon if I saved up enough money for it. I knew that they were pretty rare in Japan, hence I wasn’t expecting to find one anytime soon, until one day (not even a year after I had bought the HPA-21) I found one on Yahoo Auctions JP. Coincidentally, some extra money came up very conveniently around the same time and long story short, I won the auction and got it shipped to my country.

For this article I will be comparing the E5 studio with the HPA-21, its closest competitor (that I’ve had) in the current drive amplifiers space. Music used for testing was 80% metal, with particular focus on death metal (ex: Blood Red Throne, Spiritworld), technical death metal (ex: Archspire, Artificial Brain, Ulcerate), deathcore (ex: A Wake In Providence, Humanity’s Last Breath, Signs of The Swarm), some more atmospheric stuff (Panzerfaust) and some industrial metal (ex: Godflesh, Fear Factory). The remaining 20% was electronic music, mostly darker/more industrial ones (ex: HEALTH, Perturbator, Keygen Church).

The Chain

My listening chain for this article is as follows:
PC -> Douk U2 Pro -> Soekris dam1941-based DAC (DIY) -> Re/Leaf E5 studio OR Bakoon HPA-21 -> HD800S
Cables used are an Audioquest Carbon from PC to Douk, an Amazonbasics SPDIF from Douk to Soekris, and from it to both amps I used a pair of MIT Terminator 3 RCAs. Stock cable was used with my HD800S.

I’m not using the stock PSU with the E5 (which is one of those €20 laptop power bricks, which actually works surprisingly well), but a more competent but still fairly basic and inexpensive (around 50-60 euros in parts I would guess) linear PSU that came with the amp, which did bring a nice and noticeable improvement compared to the stock one.

Couple of notes about the Soekris: I’m using a Sjostrom Audio SSR03 PSUs for both the analog and the digital side. I’ve also put a Schaffner (FN2090NN) filter to reduce EMI noise for both PSUs.
I’ve also built the buf1961 buffer stage using OPA1612s, which brought a nice improvement in terms of separation, dynamics and background blackness. This is being powered by the psu1941, the “standard” power supply that comes as a separate PCB option when you buy the dam-1941.

Detail retrieval, Separation, Resolution

At a first listen both amps seem to actually have a pretty similar level of detail retrieval, but, after a closer inspection, the amount of information the E5 throws at you is definitely more than what the HPA-21 is capable of. The more I listen to the E5, the more I notice the microdetails it’s able to pull out from each track. No contest here, the E5 is the better performer.

An example would be with the track “1000 D E A T H S” by Spiritworld, in particular at 1:41. With the E5, the distortion of the bass gets really chunky and gritty, and while the HPA-21 feels more dense thanks to its warmer presentation, it never gets as rough (in a good way) as the E5. The hi hats also feel much more complete with the E5, while the HPA-21 makes them sound blunted and “chopped”, missing the extra harmonics and background blackness the E5 has.

And speaking of background blackness: with the E5 each instrument sounds more defined and precise, resulting in less overlap between something like the drums, the guitar and the hi hats, to the point where lower level information is much more present and also easier to spot. This is especially noticeable in incredibly busy tracks, like with some tech-death albums.

Taking the previous track again as an example, the hi hats of the HPA-21 are kind of “pushed to the side” and get overshadowed by the bass and guitar, while with the E5 they are much more clearly present and feel as important as the other two instruments.

This is also thanks to the slightly more forward presentation of the amplifier, which certainly helps in making some details stand out more, while by comparison the HPA-21 has a smoother, more relaxed presentation, making the more nuanced details much harder to notice and appreciate.

To further expand on this, I will say that the extra forwardness never gets too aggressive or in-your-face, at least for my tastes. Everything is presented with a certain naturalness to it and with an ever so slight forwardness to it that never gets too much. This ends up making something like guitars and drums sound slightly more forward, while the more nuanced instruments not only get their appropriate space thanks to the background blackness, but also get the added forwardness and overall separation that makes them really stand out, while still retaining an organic and balanced presentation.

On something like Altarage’s “Magno Evento”, a very chaotic and busy track, you can really hear how better the E5 is: you hear a lot of what is going on and you hear it much more clearly, and with great precision too. I don’t want to say you hear everything but this is a really nice step up from the HPA-21, which IMO can barely handle this track (or the whole album for that matter). It just comes off as fuzzy, less controlled, less precise, more of a “mess”.
Even with a track such as this, the E5 it never feels too aggressive/forced in its presentation, it’s a very balanced chaotic mix of instruments where everything gets its place in the soundscape in a way that feels right.

You can better hear the sheer volume of this album on the E5: it’s a constant wave of chaos, and it is big, it’s an album that is supposed to sound big and oppressive, and I think the amp does a great job at showcasing it.

With calmer albums like Banco del Mutuo Soccorso’s “Orlando: Le forme dell’amore” the Re Leaf never comes off as forward, it feels very natural and organic, showcasing its ability of being a pretty transparent amplifier that manages to better translate how an album should feel/sound in terms of forwardness and presentation, while with the Bakoon this degree of nuance between the presentations of each album gets a bit lost.

Control, Precision, Tightness, Bass Extension and Deepness

Another great strength of the E5 is its control. Everything sounds tight and snappy, with the more aggressive notes getting thrown to you very precisely. The HPA-21 sounds more loose in this regard, it can sound adequately snappy in most albums, expect the more technical and busy ones (something like technical death metal, deathcore or anything with fast drums/guitars/a lot going on) do come off pretty often as “mushier” than they should be.

A very good example is the drumming on the track “The Destroyer of All” from Ulcerate, where in the middle (4:52) gets calmer only to then slowly come back until reaching a full blown blast beat .
The HPA-21 can reproduce the slower and simpler drumming parts, but as it goes on and it gets busier, it starts to fall apart. The E5 just feels much more coherent and doesn’t really lag behind the music, always retaining a great amount of tightness and precision not only in the drums, but also letting the guitar and hi hats be better heard and enjoyed in the track.

Thanks to those aspects, the E5 also ends up sounding more powerful: you get to hear a lot more single kicks and as such, and despite them not being as dense in the lower notes as the HPA-21, those kicks hit hard and deep.
This is also true for calmer drum passages, although there are a couple of exceptions: on something that is really well mastered and that has a natural sound (no tincan-like drums) the HPA-21 just adds a bit more body and sweetness to them, while with the E5 you are getting an even tighter and deeper punching approach. Personally, I prefer the E5 tighter sound, so there’s that.

Another great example of control is with electronic music. The Bakoon does give a fuller sound to the lower notes, and sometimes it could come off as more engaging, dynamic and with more bass, but loses on the tightness of it. it just sounds “shallow” at times, doesn’t get deep or tight enough to really give that kick effect (example track: “Reaching Xanadu” by Perturbator), as if the note on the HPA-21 just stops halfway through, while the E5 continues going deeper.

On other electronic tracks that have a more present bass like “POWER FANTASY” from HEALTH’s 2020 album “DISCO 4 :: PART I” the difference in bass quantity/overall feel is actually not as much as I would have thought to be, showcasing the E5’s ability to adapt to the track in a way that doesn’t make me feel like I’m losing too much bass, getting a very similar amount of enjoyment from both amplifiers.

Another point in favor of the E5 is the amount of control and texture it gives to the bass: again, it’s quite deep and punchy, and the harmonic content in there is a pretty big step up from the HPA-21.

Overall I would say the E5 does come out on top 9/10 times just because of the sheer technical ability, control, grip and texture it gives to the bass.

Soundstage, Imaging, Width and Depth

Honestly at first I was like “yeah this stages wider and deeper, cool” but the more I thought about it, the more I came to really appreciate what the Re Leaf is doing here, probably the aspect I underestimated the most about this amp.

The best way I could describe it’s that it just sounds expansive, in all directions.
The E5 starts its soundstage from behind the headphone connectors and gets projected from there in an arc that is slightly more than 180°, while the HPA-21 starts at about the center of the cups and has its soundstage extending to like 165-170°. Not only you’re getting a wider arc, but the sound also comes from further back, making for a really big improvement on the spacing front. Once I really noticed it, It made the stage of the HPA-21 feel congested and limited.
Height also does get better with the E5, but the real standout is the width and positioning of the soundstage IMO. An overall bigger, wider and more “scenic” soundstage with the E5.

Something that is also worth noting is the shape and “edge” of the sphere that makes up the soundstage.With the Bakoon it feels like the sound is in front of you but then it suddenly gets cut off, while the E5 has its edges to be less defined, giving the sound a more natural sense of depth and staging.

Depth is also a pretty nice improvement from the Bakoon. Music just feels more layered, and each layer is pretty well defined in the soundscape, while the HPA-21 kinda loses itself sometimes, especially in busier passages.
Of course, imaging does benefit from all those aspects, being definitely sharper in the E5, more precise not only in width but also in depth and height.

Honestly not really much to say here, the E5 is the clear winner with a pretty wide stage that makes the HD800S sound grandiose but not exaggerated, resulting in a more natural/organic presentation compared to the HPA-21.

Dynamics, both Micro and Macro

At first the HPA-21 might come off as having better macrodynamics thanks to the denser sound and more abundant lower frequencies, that give a sense of added dynamic slam, but the problem is that the smoothed over upper frequencies don’t help with the “dynamics swing”: it’s strong in the lows and blunted in the upper end.

The E5 on the other hand has a dynamic swing that not only benefits from the less smoothed highs, but the leaner sound signature makes everything have a better focus, making those swings much more obvious and impactful. You don’t have to turn the volume up by a lot with this amp to start hearing some really nice dynamics, while you definitely need to turn up more the HPA-21 if you want to reach the same level as the E5 (at lower volumes).

Same thing for microdynamics: on things like cymbals or other more subtle sounds (like the picking of a guitar) the E5 is definitely ahead compared to the HPA-21, where the latter’s lower tier resolution kind of obscures those fine details, making it come off as less refined.

The E5 just feels more lively at the same volume of the HPA-21. And the more I listen, the more I realize how dynamic the E5 feels. It’s not something super obvious to me. Dynamics honestly have always been kind of difficult for me to evaluate, which might be because albums I listen to vary so much not only in style, but also in production quality, that something might be well produced but done in a different “style”, giving the impression that it has a lower production quality, while at a closer inspection it’s actually fairly decent, just different. Other times it’s badly produced but its more modern style helps it make it not sound like absolute crap, and sometimes both are just bad.

Another thing that I have noticed is that with the E5 I often find myself doing more minor adjustments to the volume pot. Some albums from different bands with the HPA-21 are pretty much equal in terms of loudness, while the E5, probably thanks to its more transparent and better macro/micro-dynamics, manages to do a better job in bringing out the natural dynamics of each album.

Timbre, Mids and Highs

I would describe the E5’s timbre as “organic slightly-dry/neutral”: it makes for a pretty good experience for the music I listen to, letting me better hear the more minute differences in timbre between two similar sounding albums. The only slight gripe I have is with the voices as they don’t really make me say “damn that’s good”. Death growls are for sure more textured, but they lack just a hair of sweetness to make them sound more “organic” to my ears.

The HPA-21 in this regard does a better job with voices more often than the E5 does IMO. It has a really slight sweetness and wetness to it that makes certain lyrics have a more emotional sound when the song calls for it. I still think the E5 still has the more refined (in technicalities) timbre though, so this becomes more of a matter of different flavors.

When we consider instruments like guitars, cymbals or other things that reside in the mid to high region of the frequency spectrum, I prefer the E5 approach of a more neutral, leaner signature, while still maintaining a good degree of organicness, as opposed to the HPA-21 wetter and less refined approach, which I’m really not the biggest fan of, especially for things like cymbals which come off as too bloomy.

Similar story for guitars, although it will depend on the genre. For stuff with more natural sounding guitars the timbre on the HPA-21 will be the more lusher option, while with some heavily distorted guitars (like in most of the stuff I listen to) the E5 will be the slightly dryer/more neutral one that will also give you the most amount of information in the harmonics.

Highs are an area where the E5 definitely wins, hands down. I have felt more than one time that the HPA-21 was sort of “capping” at a certain point in extension, while the E5 takes it a step further. Its cleaner sound does help it a fair bit in this regard. Either way, at the end of the day the E5 offers a more complete experience compared to the Bakoon.

Conclusion

I really like the E5. I feel comfortable enough to call this an amazing amp. It’s an amplifier that has kept that “honeymoon phase” magic, I’m honestly just consistently satisfied by it every time I listen to it, and it’s been about a year and a half since I’ve been listening to it. Truly an amazing amp.

I may have been kind of harsh on the Bakoon, so I wanted to clarify something: I still think that it’s a really good amp, especially for what they go for in the used market when paired with the right headphones.
At around the €/$1000 these go for I’m fairly confident you won’t find a better amplifier for the HD800S in that range and even above it up until, I would say, the 2K range, where there might be some better competition.

If the Bakoon was the “best buy” in the 1K range, the Re Leaf is the same but in the 2.5K range. Even with the very simple PSU I have for it it’s still an excellent performer. I think that with some very good 1-2K PSU this would still be extremely competitive, making for something that could scale extremely well and compete up to the 4/5K range.
Also, you can run two different E5 in a dual mono configuration, one for each channel, and supposedly that’s a very worthy upgrade so even more scaling opportunities! So yes, this might just be the current drive endgame amp.

I’m usually very conservative on the value of amps regarding their performance and please keep in mind that this is all speculative since I haven’t really tried anything in those ranges, but in this case, the way the current drive transforms the HD800S offers such a unique and strong synergy that other amps simply can’t match because of the amplifier’s topology, making me believe that something like a Bakoon or a Re Leaf would give a very fair run for their money against more expensive amplifiers.

Regarding headphone pairings I wanted to add that from what I’ve read in a Japanese blog, the Final Audio D8000 seems to have a really great synergy with this amplifier. I did not try them on the Re Leaf but I’ve heard them at the Munich Hi End on a copland amplifier, both the OG and the Pro (as well as the LE), and I can see how the D8000 line of headphones could work very well with the Re Leaf. In fact, those might be my next headphones, but we’ll see.

Now, is the Re Leaf E5 worth it? I mean, it has basically zero presence in the west and the only way to get one is to import it from Japan. It’s also a very tough resell (as one would imagine) if you decide to part ways with it, but my answer to that question is “yes”. It really is a hard sell for most people, but if you DO have those headphones it performs best with (especially the HD800S) and you DO decide to go down this path, I highly doubt that you won’t be satisfied. It’s just that good.