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HeadAmp Blue Hawaii SE Electrostatic Headphone Amplifier (Playback 56)

HeadAmp is a Virginia-based company focused exclusively on building portable and desktop headphone amps and amp/DACs. For the past nine years, however, HeadAmp has made a point of offering a series of specialized, limited production electrostatic headphone amplifiers, many of them designed by the famous headphone amplifier guru Kevin Gilmore. HeadAmp’s President Justin Wilson provides this brief history:

“HeadAmp’s first electrostatic amplifier was the KGSS (Kevin Gilmore solid state) introduced in 2003—at least five years before any competitors decided to support electrostatic headphones. The Blue Hawaii was released in 2004, and the greatly upgraded Blue Hawaii SE began shipping in 2009. The KGSS has since been discontinued to focus on meeting the demand for the Blue Hawaii SE.”

Our review subject here is the Blue Hawaii SE (for “Special Edition”, $4995 – $5999, depending on options); it is intended as a no holds barred, state-of-the-art product that complements the firm’s slightly less expensive, but also very ambitious, Aristaeus electrostatic headphone amp ($4495).


While the Blue Hawaii SE has been around for several years, it is only recently that anyone offered an electrostatic headphone good enough to show off the amp’s full performance capabilities. Specifically, we are speaking of Stax’s stunning new SR-009 headphones, which Playback recently reviewed (click here to read the review). As we said in the Stax review, the SR-009 is easily a contender for “best headphone in the world”, so it is good news indeed that several high-end amplifier manufacturers are offering products specifically for the Stax (in addition to HeadAmp, Cavalli Audio, Ray Samuels Audio, Stax, and Woo Audio have—or soon will have—notable electrostatic headphone amplifier offerings).

Of course, the Blue Hawaii SE should work perfectly well with other Stax models like the SR-007 Mk II and with late, lamented electrostatic models from Sennheiser. Given the impressive results we have seen to date from the SR-009, however, that is the headphone we used for evaluating the Blue Hawaii. This is important because, as we will see, the Blue Hawaii SE raises questions about whether it is helpful to think of the amp and headphone as an integrated system more than as individual, universal components.


The Blue Hawaii is a large hybrid amplifier with a separate power supply housed in a smaller matching box. Hybrid in this case means that the amplifier’s early gain stages are solid state, while the output stage is built around tubes (hand-picked, matched quad, “reissued” Mullard EL34’s in the Blue Hawaii SE). We asked Justin Wilson about the topology of the amplifier, and he offered this reply:



“Kevin Gilmore goes into detail on the (amplifier’s) circuitry in his HeadWize article. Apart from technical explanations in this article, Gilmore says his inspiration for the design was the expensive and rare Stax SRM-T2 amplifier which was also solid state with a quad of EL34 tubes. Stax has not had a ‘statement’ amplifier since the SRM-T2.”

The amp is designed in what we would characterize as the minimalist chic style. By this we mean that the styling of the amp is deliberately understated, so that instead of emphasizing dramatic visual details, the amp’s appearance invites viewers to savor the Blue Hawaii’s overall fit and finish quality, which are simply superb (this amp is lovingly handcrafted and looks the part in every way). If you go to HeadAmp’s site, the photos simply do not do justice to the execution of the design. The metalwork and engraving, along with the fit of the parts, is excellent.

Two final aspects of HeadAmp’s approach deserve comment. Unlike some high-end electrostatic headphone amps (e.g., the Woo Audio WES) the Blue Hawaii SE is basically offered in one configuration, with one carefully chosen set of tubes (the aforementioned matched Mullard EL34’s), one power supply, one quality level for all of the other core parts used in the amplifier. As Justin Wilson points out, “the Blue Hawaii SE has no capacitors in the signal path, so there is much less reason to have to upgrade.” Expanding on this point, Wilson adds that,


“The BHSE is available with one upgrade, an Alps RK50 volume control (possibly the best audio potentiometer in the world). Over 70% of buyers choose the upgrade. The standard volume control is a DACT stepped attenuator.”


While the main chassis and heat sink fins of the BHSE amplifier and power supply are always finished in satin black, owners can specify the color of the amp/power supply’s faceplates and trim pieces (several choices are available, as you’ll see from the photos accompanying this review).

This doesn’t mean tube rollers or aftermarket modifiers can’t attempt to tweak the design if they wish, but there is really no need to do so. The Blue Hawaii SE is aimed toward buyers who wants (and expect) the designer to ferret out the best choices rather than leaving users to “finish” the design by making various parts upgrades. The Blue Hawaii SE falls solidly in the “this product is fully optimized—no further tweaking required” camp.


The other element of the Blue Hawaii that merits attention is the batch-build and direct sale approach. When you realize that electrostatic headphones and especially a super-premium model like the SR-009, are low-volume, niche products, then you can see that a small company like HeadAmp probably has a difficult challenge forecasting demand for special-purpose electrostatic headphone amps. Their sensible response is to accept orders and, as they see demand ramp up, to run off a batch of amps to meet current orders and, in theory, to complete a few more units for inventory. Wilson acknowledges, however, that thus far production batches of BHSE’s have almost always sold out before all the amplifiers in the batch were completed. For this reason, prospective owners should understand that the best strategy is to pre-order their BHSE amps (a refundable deposit is required) to reserve a unit in the production queue. As you’ll learn in a moment, the BHSE is well worth the wait.


Consider this electrostatic headphone amp if:

•You seek an amp that works beautifully with the very clean, clear, and revealing Stax SR-009 headphones—an amp that marries resolution with a superb sense of warmth, life and integrity in the music.
•You prize an amplifier that shows how individual pieces and parts of the musical fabric are woven together to create a cohesive whole (this in contrast to amps that delineate elements of the sound, but sometimes neglect the overall sweep, flow, and “feel” of the music).


Look elsewhere if:

•You love electrostatic headphones precisely because of their ability to capture subtle nuances in the music, and therefore want an amp that lets you maximize your access to analytical detail and resolution. The BHSE is extremely good in both these areas, but some competing amps push the edge of the resolution envelope even harder than the Blue Hawaii does.

Ratings (relative to comparably-priced electrostatic headphone amps):

•Tonal Balance: 9.5
•Clarity: 9.0
•Dynamics: 9.5
•Input/Output Flexibility: 8.0
•Value: 8.5



When we talk about good amplifiers we often describe them using the same adjectives we use for the sound of speakers or headphones. This suggests that the differences between amps are as marked as the differences between speakers, which decidedly is not the case. It is pretty easy to hear the differences between amps, but the degree of difference isn’t anything like what you might experience with transducers (that is, headphones, loudspeakers, etc.). It is important to keep that in mind when comparing the review of an amp like the Blue Hawaii SE with a competing amp.


Overall, the Blue Hawaii SE seems rather neutral, with perhaps a touch of warmth and a bit of grain apparent on first listening. Interestingly, the neutrality of the Blue Hawaii SE shows up in a listening perspective that focuses on the musical “forest” as much as on the “trees”—a quality that allows you to focus on musical themes and dynamics as much as on instrumental detail or the amplifier’s underlying frequency response characteristics. When listening through the BHSE, the related short–term reaction you may notice is the desire to listen to whole tracks and to keep exploring your musical library, hour after hour. We mention these initial impressions because experience teaches that these more visceral, intuitive reactions are often predictive of responses that will linger long after our intellectual or analytical attempts to characterize or explain the amplifier’s sound.

If we break down the sonic palette, the deep and mid bass of the Blue Hawaii are very good. We know that the SR-009s can offer impressive bass and are capable of delivering dynamic and detailed low frequencies without much bloat or blur. We know this because you can hear the SR-009 deliver accurate drum and string bass sounds (accurate when compared with the sound of live music) through other amps like the Woo WES. With the Woo, you just get the sense that the headphones are being well controlled, yet supported with excellent power and drive. We’d say the Blue Hawaii SE isn’t quite as good as the Woo WES in terms of absolute neutrality (provided the Woo has been fitted with optional, upgraded driver and output tubes), because the BHSE provides a little more upper bass than we’d hear live. But apart from hair-splitting comparisons with the more costly, upgraded Woo WES, the bass of the BHSE remains top notch.


The midrange of the Blue Hawaii SE is also quite natural. Essentially, all headphones have some frequency response errors that lead mid- and upper-range instruments to sound a little distorted, especially on certain dynamic passages. The SR-009s reduce these distortions significantly when compared to many headphones, but they can, at least with some amplifiers (e.g., the Woo), occasionally over-emphasize upper midrange transients to a slight degree. We thought the Blue Hawaii SE did an excellent job of taming this tendency of the SR-009s, in the process showing just how neutral and smooth-sounding the SR-009s can really be.

In a sense, we are talking about ways in which different amps manage and balance sonic qualities that, while positive in an abstract sense, also have the potential to become double-edged swords. If we look in more detail at the upper midrange and treble performance of the Blue Hawaii SE as compared to the Woo WES (with upgraded tubes), several things become apparent. First, the Woo conveys an almost otherworldly quality of purity and continuousness, and gives the impression of offering almost boundless reserves of resolution and detail. For listeners who highly prize those specific qualities, the Woo may be the amp of choice. Second, the Blue Hawaii SE has an absolutely uncanny ability to capture the constituent elements of music in a subtle and revealing way (not quite as microscopically revealing as the Woo, but close), while at the same time—and this is hugely important—showing how those musical elements combine to form a cohesive whole. Thus, the Woo tends to deconstruct music into its component parts, while the Blue Hawaii SE reveals the parts but deftly reconstructs them to present a musical whole that makes sense.

Interestingly, planar drivers often have a bit of resonance in their measured decay patterns, so in the unlikely event that you encounter moments when the Blue Hawaii SE/SR-009 combo does sound a tiny bit rough-edged (a very rare occurrence), we can’t help but wonder if the BHSE might actually be more revealing than some competing amps. This question comes to mind because of the excellent small signal accuracy shown by the Blue Hawaii SE. Small signals are important as the basis of spatial presentation because they are what you hear


when listening for the acoustics of the venue where a recording was made (e.g., the reflections of sound off of walls and floors, etc.). We found the Stax/HeadAmp combination does a great job of revealing the spaces in which various recordings were made Likewise, the overtones of an instrument are, along with delicate transient and textural details, the source of its color, but only if they are reproduced in proper proportion to the fundamentals of notes (e.g., the decay of a plucked guitar string should be audible, but not louder than the body of the note). Once again, the Stax/HeadAmp pair comes through with overtones, textural details and the like that are easy to hear, yet perfectly integrated with the fundamental sounds of the instruments that produced them.

Related to, but different from, detail resolution is the idea of instrumental separation. In live music, one can often hear the band or orchestra as a whole, but also hear individual instruments without everything being muddled. The Blue Hawaii/Stax pair is superb at allowing you to focus you attention broadly or narrowly, just as you might do when listening to live music. This ability is a hallmark of dynamic capability, and indicates the circuitry can handle passages where signals swell dramatically or become diminished in level—all without any increase (or noticeable change) in distortion. No matter what the music does in a dynamic sense, the BHSE sounds delightfully consistent and unflappable.


As we mentioned earlier, this breakdown of sound into component parts sometimes doesn’t give you a good feel for the sonic character of the equipment under review. It gives us a list of evaluative factors we can consider, but the very process we use to perform a point-by-point analysis of the sound can create the impression that all sonic factors are equally important, which experience tells us just isn’t so.

What sets the Blue Hawaii SE apart is the amp’s well-balanced ability to capture both the inner details and the big-picture view of the music simultaneously—an area where the BHSE stands as a hallmark, breakthrough design (other amps can do one thing or the other, but not both at once). If you understand that the human nervous system is designed to be highly responsive to perceived threats, then you can see that some equipment that cleverly but consistently emphasizes certain musical details will draw your attention in a way that may impress you. But, we think there is a strong argument to be made that this process is essentially a process of distraction. A more musical method is to reveal the detail without drawing your attention to it. This allows you to focus where you or the artists desire, which is often a better approach. The Blue Hawaii SE seems to be set up to present the music in just this way.


This is important because we’ve argued that the Stax SR-009 headphones produce a subtle but meaningful qualitative shift in the presentation of music. Basically, they offer a more transparent, lower distortion, more micro-dynamically accurate lens on the music that changes the way everything sounds. That improved canvas, if you can accept the metaphor, can be treated in different ways. The Blue Hawaii SE, when it comes to transients and dynamic capability, mostly seems to just not get in the way. Beyond that, we can name a few quibbles with the sound, but on the big things the Blue Hawaii SE gets things right if you want to be able to listen to all parts of the music at will.

For purposes of this review, my comments are based on listening to the BHSE with the Stax SR-009, but Playback Editor Chris Martens has heard the BHSE with other electrostatic ‘phones and reports that the amp exhibits similar strengths no matter which electrostatic ‘phones you plug into it. It is, though, important to understand that electrostatic headphones in general, and the Stax SR-009 in particular, tend to be very revealing and to take on the sonic persona, as it were, a whatever amplifiers are used to drive them. For this reason, those considering purchasing a Blue Hawaii SE would do well to try the amp with the specific models of headphones they intend to use (a point that is especially true for those who plan on using Stax SR-009s). In a Platonic world, it would be nice to imagine that an amp could be ideal for every transducer, but in the real world a smarter and better approach is to treat headphones and amplifiers as a system, and to evaluate them accordingly.

We close by repeating our suggestion that prospective purchasers need to think about which aspects of the Stax headphones are causing them to pursue electrostatic listening in the first place. You might say “all of them” and that’s fair. But we do think there are likely to be two major, valid camps, both seduced by the SR-009, yet desiring different things from their headphone amps.


One camp will value the SR-009 for its amazing clarity and ability to retrieve low-level details, and we predict members of that camp might gravitate toward the Woo WES precisely because it, too, maximizes these same sonic attributes.

The other camp also values the clarity and detail retrieval of the SR-009, but will likely view the SR-009s as huge overachievers in both areas. Thus, members of the second camp will look to step beyond the transparency and detail of the SR-009 with an amp that offers analog-like qualities of musical integrity and dynamism. In other word, they will seek out an amp that lets them enjoy both “the forest and the trees” musically speaking. The Blue Hawaii SE could be the ideal amp for those listeners.


On Kate Rusby’s album 10 [Compass], the midrange of the song “I Wish” sounds natural and believable, and the instruments blend together well in the mix. We could, however, hear just a trace of tube noise on this track.


The song “Sweet Bride”, also from 10, has good bass detail and excellent guitar delicacy and clarity without stridency.

On The Eagles’ Hell Freezes Over [K2 HD Music], “Tequila Sunrise” has superb instrumental separation and less sibilance than we’ve heard on many other systems. Here, the cut-from-whole-cloth integrity of the BHSE makes a significant difference.

Later on the same album, “Hotel California” has great guitar dynamics and separation, while deep bass seems excellent and very well defined. Nonetheless, in direct comparison we thought the (upgraded) Woo WES had a bit more upper bass detail.

Turning to Shelby Lynne’s Just A Little Lovin [Lost Highway] the song “Just A Little Lovin” exhibited the best bass level and detailing through the Stax SR-009/BHSE combo that we’ve heard from this track. Vocals sound a bit darker than we might expect based on other headphones/amp, although this sound fit the overall character of the track really well.

Turning to the Shelby Lynne track “Willie and Laura Mae Jones”, we heard very good instrumental separation on a moderately complex mix. Shelby’s voice has a little whiteness or fine grain on it, but the dynamic flow of this track the BHSE is, in our experience, unequalled.


On Anna Netrebko’s Live at the Metropolitan Opera [Deutsche Grammophon], the instrumental and vocal separation is again excellent. The dynamics of opera are difficult, and the Blue Hawaii/Stax combo handles the swells with aplomb.


Given that the Stax SR-009 is the most expensive headphone on the market and the amps for the SR-009 are all in a pretty elevated price range, making for a roughly $10,000 investment, value is a tough topic here. Some will say that at that price we can’t be talking realistically about value. But, as we’ve said before, if value is a result of the “show me better for less” test, the Stax/Blue Hawaii SE combination does quite well. For music with headphones, we haven’t heard anything better. And, this $10k combo can do things that many in-room stereo systems can’t match at 2X or 3X the price.


In the Blue Hawaii SE, HeadAmp has produced an amp for the Stax SR-009 that does the important things right and gets our vote as the most musical headphone/amp combination we’ve yet heard.



HeadAmp Blue Hawaii SE Electrostatic Headphone Amp (amplifier design by and manufactured under authorization from Kevin Gilmore)
Output Voltage Swing: 1600 V p-p.
Stax bias: 580 V (adjustable).
Total Harmonic Distortion: below 0.3%.
Inputs: one analog balanced (XLR); two analog single-ended (RCA).
Outputs: 1 XLR and 1 RCA loop output, 2 electrostatic headphone jacks (users can choose any combination of Stax Pro-type jacks or Sennheiser-type jacks, although the Sennheiser option may be dropped soon, given that Sennheiser electrostatic headphones are becoming increasing rare).
Line Voltages: 100-120 V or 230 V; 50/60 Hz selectable.
Dimensions (H x W x D):

•Amp: 4.5” x15.5” x 13” (without tubes)
•PSU: 4.5” x7.5” x 13”
•Shipping Dimensions (both units in one carton): 32” x 19” x 11”


•Amp: 15 lbs.
•PSU: 15 lbs.
•Shipping Weight (both units in one carton): 39 lbs.

Price: $4995 or $5995 with optional Alps RK50 potentiometer

HeadAmp Audio Electronics, Inc.
Contact: [email protected]
(434) 981-2829

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