[jacal01]

  After much reading and research, I have decided to order one of these units.
 
But, I want to give the HPA-21 a real honest listen. After all, I believe this
current-mode circuit is the only thing I have not had the pleasure to try yet. And I have
tried many different amps and headphones, which usually means me purchasing it
and living with it for a while before I decide if it will stay with me, or get sold.
 
And so it will be with the HPA-21.
 
I can't wait to take delivery!

 
Hi banger.  Sorry for the delayed response, but everyone here is being a little reserved at this point.  However, don't let all the apparent contention surrounding the HPA-21 on this thread make you feel less than welcome.  Welcome to the order 

, and please post your progress and impression for us. 

 

[Dr. Roberts]

  After much reading and research, I have decided to order one of these units.
 
Can't understand the hate towards the HPA-21 demonstrated by some members here,
without even listening to it.
 
 

 
Strange isn't it since hardly anybody on HF has even heard a Bakoon amp. Too bad you don't have the LCD-3.

 

[banger]

Had the LCD-3, sold them. I tested them with the HD800 and TH-900. Their sound was between the other two. I did not like the clamping pressure, or weight either. Just did not reach for
them very often. Don't miss them at all with the HD800 and TH-900 to choose from.
 
Should receive my unit this Monday. Ordered direct from Soo In in Korea.
 
Will post my take on it after break in and some real world testing.

 

[Dr. Roberts]

It's just that much of the controversy on this thread involves the HPA-21 being able to properly drive the Audeze even though the amp was designed using the LCD-3.
 
I have the Bakoon Amp-11R which Soo In informs me is awesome with the HD800. This amp also uses the SATRI circuit of course.
 
I use the orthos with it and love the sound of classic rock I get with that pairing.

 

[bmichels]

Had the LCD-3, sold them. I tested them with the HD800 and TH-900. Their sound was between the other two. I did not like the clamping pressure, or weight either. Just did not reach for
them very often. Don't miss them at all with the HD800 and TH-900 to choose from.

Should receive my unit this Monday. Ordered direct from Soo In in Korea.

Will post my take on it after break in and some real world testing.

I Will be VERY VERY interested to read your thought about the HPA-21 with the TH/900 Since i have myself à TH-900 that i love and i am STILL looking for the VERY BEST " transportable battery-operated amp" to drive my headphone.

I bought à RWA Bellina Pro thinking it was for me THE solution, but it generates HISSS that i can't bear With the TH-900 (that is apparent l'y too sensitive for it ( ! ...). Hope the HPA-21 Will not suffer from the same problem with TH-900

Bertrand

 

[Dr. Roberts]

I Will be VERY VERY interested to read your thought about the HPA-21 with the TH/900 Since i have myself à TH-900 that i love and i am STILL looking for the VERY BEST " transportable battery-operated amp" to drive my headphone.

I bought à RWA Bellina Pro thinking it was for me THE solution, but it generates HISSS that i can't bear With the TH-900 (that is apparent l'y too sensitive for it ( ! ...). Hope the HPA-21 Will not suffer from the same problem with TH-900

Bertrand

 
 
I realize that the ATH-3000ANV is not quite the TH900 though many on HF have compared both cans and some even prefer the AT (Skylab does) but I have found that my NOS tubed EAR HP4 sounds much better with those sealed-back cans than the SS integrated Bakoon does. The EAR does cost about 3k more than the HPA-21 though and is not battery powered. Cost aside, the EAR is one of the finest sounding tube amps on the market today however.
 
Don't know about a potential sensitivity noise problem though with the HPA-21. The integrated Bakoon AMP-11R which I use has absolutely no noise using the high sensitivity HD 650. Sennheisers and the integrated Bakoon mate real well according to Soo In and my own ears as well.The EAR HP4 is dead silent no matter how sensitive the headphones are. Now the Leben 600......that is a completely different story.

 

[Llloyd]

  It's just that much of the controversy on this thread involves the HPA-21 being able to properly drive the Audeze even though the amp was designed using the LCD-3.
 
I have the Bakoon Amp-11R which Soo In informs me is awesome with the HD800. This amp also uses the SATRI circuit of course.
 
I use the orthos with it and love the sound of classic rock I get with that pairing.

 
I use the HDA-5210mk3 from which the HPA21 is very similar to with the HE-500 and it is effortless. It's my understanding that the HPA21 is like all boutique parts. One thing I noticed with the HPA21, is that (i think) it doesn't use the "upgraded" satri circuit like I would have expected. This was an option for me when I was ordering my amp but it was far too much for me. I have no doubts about the driving capabilities of this amp. I leave the volume at 1(8 o'clock, where 7oclock is totally off), and i switch to high gain for more involved listening which is a perfect volume boost for me without touching the dial.
 
Maybe someone can confirm this. Just from the pictures I saw it looked like the HPA21 had the EX circuit, which if so, seems strange considering the price of the HPA21. Not that I can vouch for any sonic advantages of the UL, but if they're selling the other one with the UL board I would think that there would be a reason for it.
 
SATRI-EX is equipped 48 transistors by miniaturization of parts, therefore it achieves super precision amplification. 
Distortion factor is 0.05%

 

SATRI-UL is equipped 72 transistors by miniaturization of parts, therefore it achieves ultimate precision amplification.  Distortion factor is 0.007%

 

 

[Dr. Roberts]

   
I use the HDA-5210mk3 from which the HPA21 is very similar to with the HE-500 and it is effortless. It's my understanding that the HPA21 is like all boutique parts. One thing I noticed with the HPA21, is that (i think) it doesn't use the "upgraded" satri circuit like I would have expected. This was an option for me when I was ordering my amp but it was far too much for me. I have no doubts about the driving capabilities of this amp. I -leave the volume at 1(8 o'clock, where 7oclock is totally off), and i switch to high gain for more involved listening which is a perfect volume boost for me without touching the dial.
 
Maybe someone can confirm this. Just from the pictures I saw it looked like the HPA21 had the EX circuit, which if so, seems strange considering the price of the HPA21. Not that I can vouch for any sonic advantages of the UL, but if they're selling the other one with the UL board I would think that there would be a reason for it.
 
SATRI-EX is equipped 48 transistors by miniaturization of parts, therefore it achieves super precision amplification. 
Distortion factor is 0.05%

 

SATRI-UL is equipped 72 transistors by miniaturization of parts, therefore it achieves ultimate precision amplification.  Distortion factor is 0.007%

 

 
 
Very interesting. The pics in the 6 Moons review clearly show the HPA-21 equipped with a SATRI-EX circuit.There is one individual that has posted on this thread recently that he ordered an HPA-21 directly from Soo In of Bakoon.  I wonder if he was offered the choice of the upgraded SATRI-UL.
 
Doubtful if this will happen soon since Bakoon amps aren't as cool as Headamps on HF so consequently few have had the pleasure of listening to one but I would be interested in a comparison of your Japanese HDK-5210mk3 and the Bakoon HPA-21. It is my understanding that Bakoon uses different parts than their Japanese cousins but of course both employ the SATRI circuit and it is difficult to get the Japanese version in most countries.

 

[jacal01]

Yes, I also saw on the 6 moons review that the SATRI-IO-EX board is the one offered in the HPA-21.  And no, I wasn't asked if I wanted an IO board upgrade.  I suspect that the SATRI-IO-UL board is the one implemented in the Bakoon AMP-11R that Dr. Roberts has, and that the reason Llloyd was offered a choice is because the HDA-5210mk3 is hand built per order, and the UL board was also available to the Bakoon Japan parent company, as opposed to the mass produced HPA-21 by Bakoon International.  I also suspect that Llloyd didn't avail himself of this option because there's most likely an appreciable cost increase associated with the UL board, and hence perhaps accounts for some of the considerable cost difference between the HP amp and its big brother. 

 

[jacal01]

I Will be VERY VERY interested to read your thought about the HPA-21 with the TH/900 Since i have myself à TH-900 that i love and i am STILL looking for the VERY BEST " transportable battery-operated amp" to drive my headphone.

I bought à RWA Bellina Pro thinking it was for me THE solution, but it generates HISSS that i can't bear With the TH-900 (that is apparent l'y too sensitive for it ( ! ...). Hope the HPA-21 Will not suffer from the same problem with TH-900

Bertrand

 
 
I actually bought a Ciúnas DAC based on an earlier comment (M-13) made in jest about your "very best" transportable DAC/amp set-up, but I haven't yet availed myself of this configuration.

 
I will say that the TH900s with the HPA-21 is a very enjoyable combination, with no detectable hiss.

 

[Llloyd]

  Yes, I also saw on the 6 moons review that the SATRI-IO-EX board is the one offered in the HPA-21.  And no, I wasn't asked if I wanted an IO board upgrade.  I suspect that the SATRI-IO-UL board is the one implemented in the Bakoon AMP-11R that Dr. Roberts has, and that the reason Llloyd was offered a choice is because the HDA-5210mk3 is hand built per order, and the UL board was also available to the Bakoon Japan parent company, as opposed to the mass produced HPA-21 by Bakoon International.  I also suspect that Llloyd didn't avail himself of this option because there's most likely an appreciable cost increase associated with the UL board, and hence perhaps accounts for some of the considerable cost difference between the HP amp and its big brother. 

 
Yeah, it was a hefty price increase for the UL board and yeah they are built to order. mine was ordered factory direct so they offer any power supply as well.  The price basically ranges from approx $1800 usd to $3,000. I think you can pay extra for attenuators, metal film resistance, or "winging resistance" as well as the EX/UL circuit. But yeah I just went with the base model as I've usually found with a lot of amps / electronics with lavish options, the base model ends up being the best value, and based off of the headfonia review I figured I'd be satisfied with the base model as well. If I had no care in the world about money I would probably go back and buy the top of the line version, but I'm more than satisfied. I was expecting slight improvements, or maybe even a side step of improvements vs the taboo, but to my ears it is superior in just about every category that I can think of.
 
I realize the HPA-21 is mass produced, but I also rememeber reading that they have an array of upgrades in the internal parts vs the japanese model(hence the battery for all out sound quality), that's why I was wondering if they used the UL board. Maybe it does not offer as significant of a sonic advantage as the other changes they made. I would love to hear the two side by side as well.

 

[jacal01]

   
Yeah, it was a hefty price increase for the UL board and yeah they are built to order. mine was ordered factory direct so they offer any power supply as well.  The price basically ranges from approx $1800 usd to $3,000. I think you can pay extra for attenuators, metal film resistance, or "winging resistance" as well as the EX/UL circuit. But yeah I just went with the base model as I've usually found with a lot of amps / electronics with lavish options, the base model ends up being the best value, and based off of the headfonia review I figured I'd be satisfied with the base model as well. If I had no care in the world about money I would probably go back and buy the top of the line version, but I'm more than satisfied. I was expecting slight improvements, or maybe even a side step of improvements vs the taboo, but to my ears it is superior in just about every category that I can think of.
 
I realize the HPA-21 is mass produced, but I also rememeber reading that they have an array of upgrades in the internal parts vs the japanese model(hence the battery for all out sound quality), that's why I was wondering if they used the UL board. Maybe it does not offer as significant of a sonic advantage as the other changes they made. I would love to hear the two side by side as well.

 
 
As would I.  Given the $1000 differential, that is the burning question.  We now know that the distortion specs are the same, so perhaps the difference in is indeed in the music fullness, its body and timbre.  I'm beginning to feel like the HPA-21 has the edge on even the Krell for warmth and body.
 
The Krell's presentation however does seem a bit smoother and laid back.  The Questyle seems to be the brightest, but also more expansive and detailed.  They all offer exceptional clarity and fidelity to the recording.  Still a lot more sampling and familiarization to go....

 

[Dr. Roberts]

  Yes, I also saw on the 6 moons review that the SATRI-IO-EX board is the one offered in the HPA-21.  And no, I wasn't asked if I wanted an IO board upgrade.  I suspect that the SATRI-IO-UL board is the one implemented in the Bakoon AMP-11R that Dr. Roberts has, and that the reason Llloyd was offered a choice is because the HDA-5210mk3 is hand built per order, and the UL board was also available to the Bakoon Japan parent company, as opposed to the mass produced HPA-21 by Bakoon International.  I also suspect that Llloyd didn't avail himself of this option because there's most likely an appreciable cost increase associated with the UL board, and hence perhaps accounts for some of the considerable cost difference between the HP amp and its big brother.

 
 
I haven't opened the case but I would be surprised if the AMP-11R comes equipped with the SATRI-UL board since my understanding is that it is the latest iteration of the SATRI circuit. The 11R is basically obsolete in a sense (although one can hear music sounding beautifully from its headphone output) with the release of the integrated 12R retailing at $5995.00. I believe that amp would come equipped with the UL. I don't know for sure but those would be my suppositions.

 

[jacal01]

$6000 for a racing car HP amp...  My palms are sweating already.

 
But I think that my amp rolling days are over.  Not much room left to grow.

 

[Dr. Roberts]

  $6000 for a racing car HP amp...  My palms are sweating already.

 
But I think that my amp rolling days are over.  Not much room left to grow.

 
 
Well, you can hook up a pair of speakers to it as well but I won't be purchasing one either. Talk about the process of diminishing returns. I know you have a lot of amps. Do you own a Master 8? If so, how does it stack up against  your Bakoon?