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Bakoon HPA-21 headphone amplifier

post #1 of 589
Thread Starter 

The thread http://www.head-fi.org/t/649056/two-high-end-bakoon-headphone-amp-japan-version-discussion-and-appreciation-thread was more or less hijacked for Bakoon HPA-21. I felt that one of the best headphone amplifiers in the world needed its own thread so please continue to post discussions, reviews etc. of Bakoon HPA-21 in this dedicated thread.



Review Bakoon HPA-21



Samsung laptop, Windows 7, JRiver Media Center 17 with 112 dB Redline Monitor plug-in

Flac-files, mostly 16/44, some 24/44-96

Wireworld Starligth USB cable

Lynx Hilo DAC

Special Wireworld XLR to RCA cables*

Red Astrachan headphone cable with ¼” to XLR adapter cable

Toxic Silver Widow headphone cable

Audez’e LCD-3 (RMA’d)

Audez'e LCD-2 (r2)

Sennheiser HD 800

HiFiMan HE-6

Ultrasone Signature Pro

Reference headphone amps:

Bryston BHA-1 with similar Wireworld XLR to XLR cables to Hilo, no ¼” to XLR HP adapter cable, i.e. balanced in and balanced out

Built-in headphone amp in Lynx Hilo (SE out)


* Explanation on the special XLR to RCA cables: Lynx Hilo only has balanced outputs and HPA-21 only has unbalanced RCA + SATRI-LINK inputs. I had the shop (Audio Concept) made me balanced to unbalanced cables according to Lynx recommendations: XLR pin 1 (ground) to shield but no connection to RCA, XLR pin 2 (+) to RCA center pin, XLR pin 3 (-) to RCA sleeve.


Redline Monitor

I always listen to headphones using the plug-in Redline Monitor from 112 dB. This plug-in fixes the stereo image so it more corresponds to listening to speakers, compare to the corresponding (analogue) functionality in SPL Phonitor. There are other plug-ins for this, but most are toys that totally change the sound. Tone Boost Isone is also good, but it changes the sound too much IMO. Head-fit and bs2b_vst use simpler crossfeed algorithms that affect the sound less but are not that effective. My current settings for RM is center level = -2.5 dB, soundstage width = 60 degrees and speaker distance = 2 m. The max setting for speaker distance amplifies high-mids (above 2 kHz) a very tiny bit, that suits LCD-3 well since it is a little bit attenuated in this area. For other headphones I set distance to 1.2 m (since this is the real distance to my monitors).


Of course you cannot use plug-ins like this if you still use CD players as your source. Most music is mixed and mastered using speakers, so things like reverb, which usually has a big stereo spread, gets too prominent when listening via headphones without crossfeed. To me that is an added effect, definitely not “bit-perfect”. Try this experiment: Listen only to the left or right channel with RM and then without RM (click on the RM icon or name for “intelligent bypass”). Which sounds most natural?


I have done all listening with Audez’e LCD-3 via the current output, unless otherwise noted.



The purpose of this review is to compare Bakoon HPA-21 with my Bryston BHA-1. In February I was lucky to be able to listen to a pre-production unit at the Stockholm High End Show. That was the world premiere for HPA-21. Then I waited and waited, remembering the clear sound from HPA-21 and wondering how it would sound like with my own equipment and music. Last year I bought BHA-1 as a “good enough / end of the road” headphone amplifier, but if HPA-21 is clearly superior to BHA-1 I intended to buy it. From an economical point of view I hoped that the differences would be so small so that it would not be worth the money to buy HPA-21.


I have also done some comparisons with Hilo’s built-in headphone amp, which reminds of BHA-1, minus some power and other qualities of a dedicated headphone amp. Since switching between HPA-21 and BHA-1 involves switching XLR cables to the DAC plus switching the headphone cable’s XLR plug it was more convenient to just switch the ¼” plug between HPA-21 and Hilo.


I will not describe HPA-21 specifications or technical solutions here since this information can be found elsewhere. For more information on HPA-21, technical details etc. please see the review by Srajan Ebaen at 6moons and my previous posts about HPA-21 in this thread.



Since there were some production delays my expectations rise for every week. Now it had a lot to live up to! Finally the shop got one of the first HPA-21 production units. Using an Esoteric CD player, Toxic Silver Widow headphone cable (kindly lent by Michael at Klutz Design) and my own LCD-3 headphones I listened to some CDs I know well at the shop. I recognized the clear sound I remembered from the world premiere at the Stockholm High End show. Robert at the shop also confirmed the differences between the current output and the voltage output.


Before leaving the shop, of course with HPA-21 and the Toxic cable with me, I tried the same setup with Sennheiser’s HDVD 800 amp, not using its DAC, driven unbalanced from the CD player and also unbalanced to LCD-3. So the setup was not optimal for HDVD 800. The sound was not bad but not in the same class IMO. The sound was kind of softer and “thicker”, maybe a little bit more low mids. Probably suits HD800 fine, though.


Here are some unboxing pictures:








HPA-21 with Lynx Hilo and LCD-3:




The only problem I have had with HPA-21 is that the nut for the left RCA socket was loose when I got home. However I could easily tighten it with my fingers and later Robert at the shop tightened it properly. Having looked inside HPA-21 he said it is very tidy built. I hope this mishap is just an isolated case. The HPA-21 has worked flawlessly ever since.





So how does it sound like? The first note I made at home was “Clear, dynamic, details, blackground”.  I noticed details and low level rhythmic figures I have not noticed before in songs I have listened to for years. Reviewers always say that, don’t they! But it is true.


I also quickly noticed that there is no lack of gain! With Hilo line out trim level set to +0dBV (lowest setting) and HPA-21 gain set to high I always set the volume less than 12:00 when using LCD-3. For modern über-compressed music I set the volume as low as 07:30. With Resonessence Concero, which outputs 1.2Vrms, the volume is a little bit louder.


It actually feels a little bit silly trying to describe the sound in ordinary terms like bass, mids, treble etc., but here we go...



The bass is excellent! It has more attack/punch and it is also more detailed compared to BHA-1. Maybe this makes it appear a little bit more prominent. On Pink Floyd’s The Wall (remaster) you can clearly hear the sharp attack when the kick drum beater hits the skin and then the short decay of the vibrating drum skin. You can of course hear all this with BHA-1 as well, but everything gets a little bit “mixed up” and “fluffy”, more “boomm” where HPA-21 presents a distinct “Boom”.  I heard similar differences when I compared the DACs Lavry DA11 (“boomier”) with Lynx Hilo (more exact and dynamic bass).



The mids is excellent! I noticed that the Hilo’s built-in headphone amp seems to have a tiny bit louder upper mids/lower highs. Reading my notes I cannot find any comment on differences in mids between HPA-21 and BHA-1. I do not connect the differences I hear with the terminology of “mids”, even though there are differences in the mids technically speaking. Hence, mids is excellent for both HPA-21 and BHA-1.



The treble is excellent! It is clean and almost “polished” with LCD-3. In comparison the Hilo amp is blunter with less attacks and, as already said, maybe a tad brighter. As for mids I rarely think in the terminology of “treble” when listening to HPA-21.



Dynamics is excellent! Notes hits you from nowhere with very “precise” attacks. Every note lives in its own space and is easier to discover, examine and enjoy than with BHA-1. When listening to electro-pop it can almost be too much with all sharp attacks. But then you just switch to the voltage output and everything softens up a bit, more like a “normal” amp. The sound of Hilo’s built-in amp and, to a lesser degree, BHA-1, can almost be perceived as being compressed compared to HPA-21. This makes it harder to match the levels by ear.


The rest

Imaging, blackground, micro details, PRAT etc., everything is excellent! Someone described another Japanese Bakoon headphone amp as having a “slight v-shaped tonality”. This is not true for BHA-21 IMO. HPA-21 and BHA-1 are both flat, but it is true that initially you may perceive HPA-21 as being more V-shaped while BHA-1 has a “fuller” sound. I recognize this phenomenon from when I bought my Event Opal monitors. The Opals’ have less distortion than some other monitors so they may sound a little bit on the “thin” side. But when you listen carefully everything is there, having the correct level. What’s missing is the distortion, which normally makes a more initially impressive sound. I have my own term for that type of sound, I call it “paper cone sound”. Think of the sound from an old speaker with a wobbly paper cone. It hardly sounds correct, but nice and “cozy”. Perfect for guitar amps! smile.gif


BHA-1 is a very very good headphone amp! It definitely does not sound like a Marshall stack on 11 (or 1)... smile.gif You have to compare these amps side-by-side to be able to describe all the differences. When listening only to HPA-21 it is an excellent amp. When listening only to BHA-1 it is also an excellent amp. It is when you switch between these amps that you start to notice, and also to learn and remember, the differences.


Note that HPA-21 is in the “output = input” category. If you want a colored sound to your taste or maybe to compensate for other components in the chain, if too many details distract you from the music or if you do not want the slightest hint of sibilance or edgy sound on badly recorded music, this amp may not be for you.



Now we are getting to the heart of the matter. HPA-21 presents all instruments, voices, tiny sonic and rhythmic details, effects, you name it, so naturally and clear! The music is just there for you to listen to. It grabs your attention. You do not listen to a DAC with a fancy headphone amp, you listen to the music, period. With BHA-1 you tend to listen to “technical” details, at least when reviewing, while with HPA-21 you soon forget about all that and listen to the music instead. Here are some comments from my initial listening notes:


Switching to BHA-1:

"Ordinary" again. Not bad though.

Not as clear.

Lots of details!

"Thicker", more of a "wall of sound" where everything gets mixed together.


Switching to HPA-21:

Precision! Exactness! Details! Calmness! Naturalness! Unsmudginess! MUSIC!


The following episode is typical for HPA-21. I had switched to BHA-1 and listened to Pink Floyd The Wall (remaster), 2nd record. Sounded really good! Roger's voice was maybe a tad brighter than I remembered from HPA-21. While listening to the record I also read a review. I saved half of the review for later. When I had listened through the whole record I switched to HPA-21 and matched the levels. I then listened to the same record again. I could not start reading the second part of the review since my attention was drawn to the music, even though I had just listened to the record! I noticed the more detailed kick drum, the clean sound, how I could almost touch all instruments, I noticed small details etc. Finally I managed to continue reading, but I was always present in the music in a way I was not with BHA-1. I also noticed my right foot started moving... This is typical for HPA-21, the music is just there and always grabs your attention.


A week later I listened to and viewed Peter Gabriel’s Red Rain from Growing Up Live from YouTube, first on HPA-21 (because I couldn’t stop myself), then on BHA-1, then once again on HPA-21. On a way too loud volume... It was ridiculous. HPA-21 presents a clean, dynamic, studio-like sound with you present at the concert. And the bass, wow! You feel the joy of the musicians, you’re inside the music. With BHA-1 you get most of the details, but everything is kind of mixed up into a mush and you are not at the concert in the same way anymore, you are listening to your headphones via a good amp. So you do not need high-res audiophile recordings to get the best out of HPA-21. Of course high-res classical music also sounds excellent via HPA-21 (I have listened to that too). But with HPA-21 you can easily concentrate on the music, resolution is secondary.


According to Bakoon the SATRI circuit has no slew rate and you get 1/10th of the headphone distortion with the current output. Now I know how that sounds like.



I have done some listening with HiFiMAN HE-6 (leather earpads, standard cable). When switching from LCD-3 to HE-6 you get this “wow so clear” experience since the HE-6 treble is a little bit exaggerated. HE-6 has a more “hifi” type of sound than the “monitor” sound of LCD-3.


“Can HPA-21 drive HE-6?” Yes it can, IMO. For the current output I set the volume to 12:00 - 01:00 with most modern records with a level around -3dBFS. For quieter records (around -10dBFS) I go up to 03:00. When using the voltage output and listening to quieter records you may need a DAC that outputs the standard 2Vrms. Hilo set to +4dBV gives enough juice for this.


The bass has great impact, but not the attack of LCD-3 or HD 800, more like a sub plus satellites. The mids is very clean, but I miss the fullness of LCD-3. The treble is crispy but slightly exaggerated. All this is the nature of HE-6. HPA-21 does nothing to compensate for the tonality of HE-6. There are perhaps other amplifiers with a sound more adapted to HE-6. But instead of +1 + -1 = 0 I always prefer 0 + 0 = 0.


I enjoyed listening to HE-6 with HPA-21. Your brain quickly adapts to a new sound signature. Darker records now get some treble and sound “normal”. However it can easily be too much since HE-6 in itself makes everything sound “cleaner than the real thing”. Modern electro-pop with lots of treble and transients, like the excellent record “Tomorrow” by Niki and the Dove, is perhaps not a perfect match for HE-6. But I still enjoy the music, albeit at a lower volume.


The difference between the current output and the voltage output is useful with HE-6. The voltage output sounds more like a "normal" headphone amplifier while the current output presents a knife-sharp and exact sound with a very powerful bass. I agree with what Srajan says regarding this matter: "Now paler mellower voltage drive didn't seem boring but welcome and more natural. This was the one exception to the general rule that current mode always beat out voltage drive - playing the HE-6 at very high levels." I have to add that some sub-bass is lost when using the voltage output.


When switching to BHA-1, using balanced inputs and output, I have to change the Hilo output trim level from +0dBV to +4dBV to get enough juice for HE-6. The more ordinary amplifier type of sound in BHA-1 makes it easier to listen to HE-6. Voices get a little bit fuller and rounder. But at the same time I miss the dynamics, the raw power, the exactness and the clearness of HPA-21 (both outputs). I prefer the HPA-21 voltage and current output to BHA-1. However the BHA-1 bass is a good combination of the fuller voltage output and the more sub-bass current output on HPA-21.


If you want the sound to be as clear, detailed, dynamic and exact as possible out of your HE-6, try HPA-21.


HD 800

Since I bought my (first) LCD-2 I have not listened to my HD 800 because I think they are too trebly. It got a little bit better when I bought the Cardas cable (used for this review) but still too much treble (and too little bass). But here comes HPA-21...


Like HE-6 HD 800 presents a “cleaner than the real world” type of sound. But it is much easier to listen to HD 800 than to HE-6 IMO. It has been said before, there are similarities between the LCD-3 sound and the HD 800 sound. It probably has something to do with the exact control of the diaphragm.


Do not forget to switch the gain to low before plugging in HD 800! I did once and wondered where all the hum and noise came from. Then I pressed Play... basshead.gif  It was a good thing that Soo In adjusted the low gain on HPA-21 at the last minute, I think the volume range suits HD 800 well. I set the volume up to 12:00 for quieter records.


The sound with HD 800 plugged into the current output is organic, very detailed, soft and airy with extended treble. While the treble is a little bit exaggerated it is not as sharp and edgy as with HE-6 but have a rounder character instead. When switching to the voltage output you get the trebly sound I associate with HD 800. Voices get a kind of nasal and trebly "Donald Duck" character. With the current output the sound is more "grown-up". Voices get more fundament and are less forward. Everything gets more organic. Interestingly this difference between the voltage output and the current output does not exist for LCD-3 or HE-6.


The bass can be compared to the bass from a smaller monitor speaker, very alert, dry and clean but the real full-blown bass with the physical sub-bass from a bigger speaker is not there, like it is with LCD-3. Note that HD 800 has some sub-bass, but more in an “analytical” way, not as physically present as with LCD-3. It sounds like HD 800 almost has some extra energy around 100Hz. The bass character is similar to the LCD-3 bass, while the bass from HE-6 lacks the “punch” but has a lot of sub-bass instead.


The mids is super clean and organic but a little bit distant, like you want to move closer to the speaker to hear it better. As with HE-6 I miss the fullness of LCD-3 a little bit. The treble is super detailed, crispy and exact. Strangely enough I’m not much bothered by the treble peak, a little bit dependent on the music though.


The sound stage is über wide and airy. It is quite amazing, almost like an added effect! It is very easy to listen to and, with suitable music, probably will affect your state of mind. Hakuna matata! rolleyes.gif  Remember that I use the RM plug-in. Without it the soundstage is way too artificial.


When switching to BHA-1, using balanced inputs and SE output, the treble gets sharper, more of the standard HD 800 sound again. But the bass is great out of BHA-1, a little bit less defined but a perhaps a little bit more physically present than with HPA-21. Switching back to the HPA-21 voltage output you get almost the same sound, but a tiny bit more organic, less sharp and less trebly. Maybe you lose a little bit sub-bass compared to BHA-1. Then you switch to the current output and the sub-bass is back again, but more distinct than with BHA-1. And voices are organic, you can almost touch them. This is fun!


I will definitely start using my HD 800 cans again. HD 800 fans, you have a new amplifier to check out!



If you forget to turn off the power when you do not use it for a while the batteries may be dead when you want to start listening again. Then you have to wait for the batteries to re-charge. You will soon make a habit to turn off the power when appropriate, but sometimes you will forget...


There are no balanced inputs. This is understandable since Bakoon have their own SATRI-LINK standard instead, but if you do not use other Bakoon products (like their upcoming DAC) with HPA-21 the preamp or DAC of your choice probably has balanced outputs at this price range. However sound wise this should not be a problem in most cases (for example my special cables are just 50 cm long).


Final words

If you read this you have most probably already read the review by Srajan Ebaen at 6moons. I agree with what Srajan says, but you need to listen to HPA-21 for a while to fully understand it.


Do I exaggerate? Not IMO. Magnifying maybe. I only try to describe what I hear. YMMV, of course.


Of course I bought it! I guess I will only use my BHA-1 when the batteries in HPA-21 are dead. Once again I have reached the end of the road when it comes to headphone amps, but now at the highest possible end. I cannot imagine how any headphone amp can be better than this! Different, yes, but better, no.


OK, one last analogy... Compare listening to music to looking out through a window. Some windows are dirty. Some windows are colored. Some windows have very old glass, and while very clear they distort the view in funny ways. Some windows do not distort the view in any noticeable way (like for BHA-1). But you still look through glass. Then you open the window. This is HPA-21. Welcome to the music!



I will add comments on using other headphones with HPA-21 (SP, LCD-2).

Edited by CanDude - 5/28/13 at 3:26am
post #2 of 589
Thread Starter 

Here are all my (and others) questions and the answers I got (via proxy) from Soo In at Bakoon. Most of the Q & A were first posted in the previous thread. I will update this post with new Q & A.


Q: Why no balanced output?


A: There is no need for balanced output as our SATRI circuit is current based topology and is far stronger against outside noise (also in longer runs) and maintaining signal purity when it comes to transferring signals. For example, you may connect our two equipment via SATRI-LINK with a pair of 100 meter long interconnect cable (BNC equipped) and still sees no signal loss.


Q: Why no remote control?


A: We do not consider the remote controller is necessary for headphone. You are not likely to listen to headphones 10 meters away. It's also possible to develop better sounding products without the remote controller as you won't have to worry about all the internal EMI generating from the controller IC. We use a high quality Tokyo Ko On VR in the HPA-21 and the result is very good.


Q: Amps normally perform the best when they are warm. Do I need to "sacrifice" one half to one hour of the battery time to warm up the amp before I get the very best performance out of it? Or is there non-battery power connected to the amp (to warm it up) when the power is off?


A: This is due to behavior of bias circuit and with the new advanced bias circuit inside the HPA-21, you will get optimal result starting from 10 minutes or so.


Since I have had some problems with a recessed headphone socket on my Lynx Hilo, and on the picture of the final production unit the sockets seem a little bit recessed, I had some concerns about this (silly me).

A: The internal PCB has been redesigned for the new thicker front panel so that the sockets fit perfectly as before.


Q: Concerning the question on balanced output I did not mean that there is a problem with noise reduction. What I was referring to was that for a so called “balanced” headphone output both channels are totally separated and each channel has its own ground or minus connection (normally a 4-pin XLR is used), as opposed to an “unbalanced” or "single ended" headphone output where both channels share the same ground. Maybe this is not a problem in a current driving amp? Doesn’t the current for the two channels “affect” each other in some way via the common ground? Even though the output resistance is 2.5MΩ, does the movement of the voice coils still generate any current, altering the movement?


A: The balanced driving methodology is effective when the ground is not clean or not precise enough. Our SATRI Circuit's ground impedance is very low and highly precise so that the circuit performs better than the balanced driving method.


Q: When the battery runs out of power, does HPA-21 automatically switch to recharge mode, or do I manually need to turn off the power switch to start recharging the battery? Not used to battery power, I will forget to turn it off and the next day the battery will be empty if it is not automatically recharged.


A: When the battery runs out of power, it switches off automatically but does not star to charge automatically. You still have to manually turn off the power switch as the recharger only begins charging when the switch is physically at the off position. This method is to minimize the recharger interference during the play time.


I can add that I think I’ve already learnt to switch it off while I’m not listening. The battery recharger has a handy LED that is green while not charging and turns red when charging the batteries.


Q: One thing bothers me a bit with the HPA-21, the battery. Although I understand the advantages of using a battery I'm still concerned about the longevity/life-time of the battery. A $3000 rendered more or less useless after a couple of years usage isn't very appealing. Also, is it possible to change the battery without too much hassle (i.e. sending it to S. Korea.)?


A: We are using one of the best and most reliable batteries from Samsung SDI, they guarantee 500 recharge cycles for the battery to reach at is 80% lifetime capacity. So after about 3500 hours, its running time will drop to around 5 hours, but is still usable. (also consider that one can use more than 3 years with 3 hours/day usage)


The two battery packs inside the HPA-21 are easily replaceable and will cost approx. EUR 125 + VAT and labour to replace – if ever needed.

Edited by CanDude - 5/23/13 at 4:03pm
post #3 of 589
Thread Starter 

Alex from Audeze listened to HPA-21 + LCD-3 20 minutes or so at the High End Show in Munich and then he noted that this was the best sound he had ever heard from their LCD-3!

post #4 of 589

In terms of sheer technicalities, the Bakoon HPA-21 was undoubtedly the best single-ended headphone amp I've heard. It is an excellent pairing with Fostex TH900 too.

post #5 of 589

Committed.  wink.gif

post #6 of 589

Great review, thank you !


Having lived with the Amp-11R for sometime now, I know Bakoon is top notch quality.

I love that the headphone amp was not an afterthought of this integrated !

It's great to see them putting out another wonderful product that gets people excited about music again !


I actually preferred my d7ks (on the lowest output settings) to my LCD-2's (middle output setting) on the Amp-11R.

Hopefully soon I will get to try the LCD-3's !!

post #7 of 589

Finally set up my HPA-21 this weekend.  These are my initial impressions (all on current output) per my notes:


Coming off my EAR HP4 tube amp, and with TH900 phones, my initial impression upon plug in was a disappointing comparatively dark sound.  Almost muffled.


Noticed a distinct loss of a layer of texture re. my HP4.  After these initial impressions, I started to pay attention to the HPA-21 in absolute terms.


The sounds are reproduced intact.  The vocals are articulate and the instruments sound true, especially the percussion.  No bloat or smear.  No sibilance.  Good data retrieval.


Good piano. Mids are accentuated?


Good air.  No compression detected.  Ample space between individual instruments and vocals.  Soundstage carryover from the TH900s?  If so, nothing is lost in signal amplification.


Very good mids and bass reproduction.  If anything is missing, it might be a slight treble rolloff?  Most probably my music selection for the evening’s entertainment.  Aside: Did anyone else go to the Bottlerock music festival weekend before last?!


Musical engagement increasing.  Non-fatiguing listening.  Probably the best thing one can say about a SS amp (e.g. vs. Soloist).


Periodically, I found myself getting up to adjust the volume downward.  This volume creep can be either amp warm-up or burn-in.  I suspect the latter, since I also noticed the music richness/texture is increasing along with the increasing engagement.  Very satisfying and full sound at this point.  The veiled darkness, if any vestigial lingering at all, has completely become a non-issue.


Switched to my LCD-2s.  Discerned less of a difference between the HPA-21 and the EAR HP4, which is a very good thing in terms of texture and sound reproduction fidelity.  A good tube amp will always be a tad smoother, however, which will be the output transformer quality reporting in.  Nothing to do about that; the HP4 is a higher end amp.  The fact that the HPA-21 compares favorably at all is a distinct mark in its favor.  Admittedly, the TH900s are special; they enhance everything, especially bass.  I guess that’s what “euphonic” means.


To snejk:  I listened with my LCD-2 orthos on low gain, and with the volume at 9 o’clock.  My guess is this amp has more than sufficient power to drive your HE-500s.


All in all, the Bakoon HPA-21 showcased the TH900s to good advantage.  I think that the LCD-2s are a good match, too.  If a general headphone match statement can be made at this point, perhaps considering its dark beginning, the HPA-21 might best be matched with “brightish” headphones, although I don’t consider either the TH900 or LCD-2 particularly bright.


Last evening postscript:  Continued listening with my LCD-2s to maintain a more neutral observation.  There was a seminal moment when I heard a distinct wonderfully full low frequency response reminiscent of the TH900, as in “Booya!”.  This is most likely the continuing amp burn-in.  If so, the prospect is exciting, since my Bakoon is already sounding pretty damned good IMO.  This may very well be the most “tubey” sounding SS headphone amp around, albeit with the caveat that I’m only comparing it against my HP4, without a whole lot of SS amp auditions under my belt.


You guys are going to love this amp.  Perfect for desktop.  Anyone wanna buy my Soloist?  wink.gif

Edited by jacal01 - 5/21/13 at 6:56am
post #8 of 589

Thanks jacal!

Sounds promising, although the comment regarding muffled sound with the TH900 is a bit worrying as I think the TH900 is on the border on being to warm as it is. 

post #9 of 589

That was only the initial impression on startup.  The amp subsequently opened up beautifully.  Its roots may be dark, but the bloom is open and airy, with tons of musical detail and individual placements.  You will not be disappointed.


It's becoming apparent that the HPA-21’s unique niche might be its remarkable clarity of individual instruments and vocals and faithfulness to the original music, and yet presenting a rich and full bodied gestaltic engaging sound.  A fine balancing act, but the HPA-21 somehow manages it with seemingly effortless aplumb.  I think that “euphonic” may also be applied to the amp, and this is with the LCD-2s.  Can you imagine what the combination of the HPA-21 and TH900s must be like?


I’m continued to be impressed with this amp.  I’m now a believer of current driven output for headphones.  This amp needs to be heard to fully comprehend ‘distortion free’.  It’s not only detectable, it's palpable. 

Edited by jacal01 - 5/21/13 at 10:23am
post #10 of 589
Thread Starter 
Originally Posted by kcee View Post

Great review, thank you !


Having lived with the Amp-11R for sometime now, I know Bakoon is top notch quality.

I love that the headphone amp was not an afterthought of this integrated !

It's great to see them putting out another wonderful product that gets people excited about music again !


I actually preferred my d7ks (on the lowest output settings) to my LCD-2's (middle output setting) on the Amp-11R.

Hopefully soon I will get to try the LCD-3's !!


Thank you!

I wonder how things are going for Tyll? And Andy?

post #11 of 589
Thread Starter 

I’m happy that you like it jacal01! Good to not being alone. When you seem to be almost alone in the world praising something this much you sometimes think “is this really true, do I exaggerate too much, am I crazy”. But then I just listen to HPA-21 again and I’m in heaven, feeling sorry for everyone not owning an HPA-21...  biggrin.gif


I just did a little experiment. I listened to Robbie Robertson’s song Straight down the line from the excellent record How to Become Clairvoyant. You could say that the tonal balance on the record is reminiscent of the LCD cans... First I listened via HPA-21, then via BHA-1. I tried to adjust the volume to the same level by ear. Then I went back to HPA-21, again trying to get the same volume level by ear. Then I measured the sound levels, using an app in my phone (so no higher precision here). The volume level was approx. 1dB lower for HPA-1. Then I adjusted the volume on HPA-21 and Hilo’s built-in amp to match as closely as possible using the phone’s app. When switching between HPA-21 and Hilo’s amp I perceive HPA-21 to be a little bit louder, especially on dynamic songs.


I think I distinctively turn down the volume on HPA-21 because it is so dynamic and clean compared to the other amps. And when you turn down the volume you also perceive the treble as more attenuated due to the equal-loudness contour. Maybe not noticeable for 1dB but maybe noticeable if you turn down the volume on HPA-21 even more. This could be part of an explanation of the darker sound. Or not!  tongue.gif


Another possible explanation is the lack of slew rate and distortion in HPA-21. As you know when you add a very tiny amount of distortion to bass it suddenly sounds “better”, “fuller”. For example the bass on DA11 is perceived to be stronger than the bass on Hilo, which is more dynamic. I think this is true for all frequencies. When switching to the other amps after listening to HPA-21 I hear kind of a “haze” surrounding everything, making the music more compressed, “flatter” and boring. When treble attacks are “smeared” due to timing problems in other amps (slew rate) and you multiply the distortion ten times I guess you get this “haze”, that also adds energy to attacks. The length of a sound decides how well you hear it. That’s why gun shots etc. always have a lot of reverb added in movies. Without the reverb you would not hear the gun shots as well. I’m not making this up, BTW. So if an amp makes a percussive treble sound a tiny bit longer you will hear it better. However this is just a theory I’ve made up... tongue.gif Still, when I really concentrate on percussive trebly sounds I think the actual attack is as strong on HPA-21 as on the other amps. But it decays faster, which makes it a little bit easier to hear on the other amps when listening more normally.


A lot of theories and no scientific proofs, I know. This is head-fi!   beerchug.gif


Also don’t forget that HPA-21 is very transparent. So my review is also a testimony to Lynx Hilo. When switching to Concero I cannot describe the sound in the same glorious way since that DAC is not as good. I’m also surprised that different records sound so different. This is as always a good sign that you just bought an excellent piece of equipment!

post #12 of 589

Only us?  I guess everyone else is obsessing over their BHA-1s and GS-Xs.  Their loss.  Of course they won’t know what they don’t know.  wink.gif


My own growing opinion after several nights of listening is that the HPA-21 has an extensive warm up period, rather than a one-time burn-in.  The analogy I used above about a blossom opening up is actually a good one.  I think the cold amp starts out closed and dark, and then opens up continually, adding successive layers of texture, air, clarity, and fidelity as it warms up.  And this period of sonic growth is fairly long, maybe even two hours or longer, before you’re totally enraptured by the sound and fully engaged in the music.  Then it is literally bliss or nirvana or heaven or however we try to inadequately express what we’re hearing and feeling.  It really needs to be experienced, and with a warm amp, rather than objectively reviewed for advice on purchase.  It may sound cliché, but you really hear all your music again as if for the first time with fresh appreciation.  How do you put that immersion feeling into words?  In fact, that’s what I’ve been doing these past evenings, revisiting old favorites to hear previously unrevealed glories.  I slapped on My Bloody Valentine’s shoegazing classic Loveless the other night to see if the amp would tease the recessed vocals out of the overall ambient droning wall of sound because of its extraordinary clarity ability, but alas, I found that there is a limit to the amp’s divining prowess in that it can’t enhance what wasn’t there in the original recording.  In that sense it does illuminate badly engineered records.  If the recording is compressed or poorly mixed, the amp will reveal the bad recordings from the good simply by what’s not there.  But if it is there, well….  tongue_smile.gif


This extended warm-up may be the disadvantage (only?) of the current driver output circuit topology, but I think it’s the reason why I found myself repeatedly getting up to turn down the volume as the amps’ sonic signature opened up to everything: body, frequency response, musicality, enticement… you name it.  I’m out of quality descriptors.  It really needs to be heard to comprehend.  Words are inadequate, and have been so overused around here with these repetitive equipment reviews that now they tend to be dismissed as glib and trite or subjective hyperbole from someone who’s ballyhooing his purchase decision.

Edited by jacal01 - 5/23/13 at 7:26am
post #13 of 589
Thread Starter 
Originally Posted by CanDude View Post

Here are all my questions and the answers I got (via proxy) from Soo In at Bakoon in one post. The Q & A are copied from two posts in the previous thread.



I have added Q & A with Soo In to the second post.


Concerning the warm up period Soo In says "you will get optimal result starting from 10 minutes or so."

Tonight I listened to two songs approx. 15 minutes after HPA-21 was turned on. Then I listened to the same songs again approx. 1 hour 45 minutes later. Your hearing is constantly changing, but jacal01 you could be right. At the first listen the sound was maybe a tiny bit colder. You may also call it clearer. At the second listen the sound was more organic and relaxed. Maybe...


Maybe it is a good thing to have HPA-21 placed over Hilo. Hilo gets quite hot after a while and it of course helps to heat up HPA-21 faster.  wink_face.gif

post #14 of 589
Thread Starter 

Toxic Silver Widow vs. Red Astrachan LCD-3 headphone cables with HPA-21


The first day I had HPA-21 at home I also had the possibility to compare the Toxic Silver Widow cable (used on shows by Klutz Design) with my own Red Astrachan cable. This is my micro review based on the notes I made and what I remember.


Toxic Cables should be familiar for everyone owning a headphone and reading head-fi. Toxic Silver Widow (SW) is a popular and often recommended cable for LCD-2/3. The Red Astrachan (RA) cable is made by the Swedish Audez’e importer KDM. This is the cable I currently use, see my red astrachan review.



When comparing the two cables SW has a little bit softer more refined presentation while RA is more “blunt”, "in your face" monitor-like. SW has more space, more air and almost places all instruments in a room while RA presents a more distant precise “direct-miked” sound. Funny, it seems to be less differences between HPA-21 and Hilo’s built-in amp when using SW than when using RA. RA in itself has almost an "HPA-21 effect".



RA has a little bit stronger (sub-)bass than SW, more physically present. This is the bass I absolutely love! However the RA bass is perhaps a tiny bit more bloated while the SW bass is cleaner with a higher resolution, for example bass drum details are a little bit easier to discern. While it may be a little bit easier to follow bass lines with SW this could be a result of the SW sub bass being a little bit attenuated compared to RA and therefor the bass as a whole being a little bit “clearer”.



The more room-like sound of the SW cable could be the result of SW having a tad more mids than RA, or maybe that SW can reproduce finer details in the sound, like reverb tails. SW voices are fuller, RA voices are more distant (maybe lacking some lower mids compared to SW).



The SW treble is a perhaps a little bit attenuated compared to RA in the same way as the sub-bass is, but it was not something that I noticed that much.



I think SW has somewhat softer attacks than RA. When switching from RA to SW it is almost like putting a thin blanket over the sound. Attenuated bass, treble and softer attacks. More mids. Maybe it is the RA mids that are attenuated? With SW I miss the attacks and dynamics of RA, but I like the sense of space. With RA you startle at some bass attacks and also some sharp piano attacks. This does not happen with SW that often.



The comfort for SW is very good. It is not a “shoe string” like the Q-Audio cable but it is very comfortable. The comfort for RA is not that good. A Swedish magazine described it as a “snake”. With its own will, I may add. But I have learned to live with it because of its sound.


Final words

The sound differences between these cables are far less than between HPA-21 and BHA-1, but still add to the total sound experience.


For a sense of space, room information, tiny details and comfort SW wins.

For dynamics, bass “slam”, a “monitor” sound and maybe the treble RA wins.

So the overall winner is… both!  blink.gif


Hopefully I will be able to compare the new Toxic Virus cable with Silver Widow (and my Red Astrachan) soon. Driven by the current output on HPA-21, of course!

post #15 of 589

Nice impressions, on amps and cables.


One thing bothers me a bit with the HPA21, the battery. Although I understand the advantages of using a battery I'm still concerned about the longevity/life-time of the battery. A $3000 rendered more or less useless after a couple of years usage isn't very appealing. Have any of you guys heared or seen anything about that? Also, is it possible to change the battery without to much hassle (ie sending it to S.Korea..)?

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