[Ivabign]

  The headphone plug and the USB are on opposite sides of the HA-2 ?  Reminds me of my ancient HRT iStreamer.
 
That must be a total PITA to carry inside one's trouser-pockets, or, in my case, the inside breast-pocket of a men's sport-jacket.
 
Yeah, I know...you can get a right-angled cable for the headphone and have that on the bottom end as there is no, AFAIK, right-angled Lightning cable.
 
Form factor and usability are very important to me.
 
Any solutions? 
(I admit to having read only the past ~10 pages.)

Honestly with the stubby USB/Lightning cable I am now using, it isn't a huge bother to put in a pocket USB side first - and the size is perfect to mate with my iPhone 6 in its case....
 

 

 

 

 

 
Uh oh - you can see the Hot Wheels on my desk in the last picture 

 

[Neo Zuko]

My one user issue so far is that the iPhone 6+ is so much bigger than the HA-2 that the stack is less than ideal for the rubber band placement. I think there should be a bigger HA-2 with more battery inside to stack better with 5.5" phones that are all the rage today, plus be of more use charging your phone, etc.

A center plate with another set of rubber bands would also work. Then the two items can mount at different points separately to the center plate.

 

[howdy]

My one user issue so far is that the iPhone 6+ is so much bigger than the HA-2 that the stack is less than ideal for the rubber band placement. I think there should be a bigger HA-2 with more battery inside to stack better with 5.5" phones that are all the rage today, plus be of more use charging your phone, etc.

A center plate with another set of rubber bands would also work. Then the two items can mount at different points separately to the center plate.

You should get the IPod touch 5g with it, fits perfect and is really slim and light. And you get your phone back.

 

[SteveNZ]

  pm-3 have only 26 Ohm impedance and quite high sensitivity at 103 db, so i think the low gain is fine for them
 

I have the HA-2/PM-3 combo and they work great. No need for high-gain mode at all.

 

[alerma]

I've found interesting information about HA-2 on OPPO Japanese site. There is a product feature description that seems missing in US variant on US OPPO site. According to the description (Google translated) HA-2 has TRRS output connector and uses separated grounds design, similar to ZX2 and Hifiman. 
 
The original link: http://www.oppodigital.jp/products/headphone-amp/ha-2/
 

[size=15.0799999237061px]Stereo headphone output which adopted the GND separate design[/size] Traditional portable audio equipment, deterioration of channel separation could not be avoided due to the commonality of Lch and Rch of GND of the headphone output (ground). Stereo headphone output of HA-2 will be to adopt a design that was completely separate the GND in the left and right up to the jack part of the four-pole type from the amplifier circuit (※), we are held down by thorough deterioration of channel separation . As a result, we have achieved a wide sound field reproduction is not only clearer localization.Also is possible GND separate drive in combination with PM-3, which has become a GND separate design.

※ 3-pole plug of the earphones, there is no hindrance to operate even use our headphones. Earphone of 4-pole plug in the case to take advantage of the GND separate design, please use headphones. Pin assignment, please refer to the following image.

 
The another article in Japanese has a lot of talking in great details about advantages of separated grounds design, see it here (use google translation): http://www.phileweb.com/review/article/201505/13/1626.html
 
In addition the article has some valuable information about internals of HA-2, see below (google translated):
 

 TI's op amp to headphone amplifier "OPA1602", as well as constitute a differential amplifier circuit using a "OPA1662". In addition it has the company's headphone amplifier IC and "TPA6120" and analog amplifier design for mounting a class AB current amplification transistor. By using a part which has been sorted while achieving a compare match to the output stage, and is thoroughly care both power and quality of the output signal.

 

[zilch0md]

Thanks alerma!
 
This is very interesting stuff, but it immediately begs the question:
 
If Oppo designed both the HA-2 and PM-3 with TRRS jacks instead of TRS jacks, why aren't they offering TRRS-to-TRRS cables for the PM-3?
 
It's especially curious, given this glowing account of the benefits of using a TRRS-to-TRRS cable:
 
Quoting page 4 of the Google-translated article at http://www.phileweb.com/review/article/201505/13/1626.html:
 

Headphone PM-3 is, when combined with HA-2, corresponding to the "4-pole ground isolated output" using the adopted cable 4-pole stereo mini terminal. Replacement cable that comes included with the PM-3 thing of the three-pole type, but this time the top of the cooperation in OPPO Digital Japan to deal with the product of OPPO, and OR ANTICIPATED your prototype of the four-pole ground isolation cable for PH-3 Te, and I had the opportunity to be able to listen to the sound with special 4-pole ground isolation. 
 

Capable of 4-pole ground isolation connection, headphone cable employing a 4-pole stereo mini terminal prototype. 
Because it is made of the same material as the PM-3 included in the three-pole cable, it is possible to pure comparison
 
 
Listening to the cable of 3 terminal and four terminal, we tried the effect listening while re-cable to the music each alternately. HA-2 is being mounted to two stages of gain switching function, since in combination with the current PM-3 obtained good listening sense "Low", and listened by setting here. 
 

Above 4-pole stereo mini terminal. Under the 3-pole stereo mini terminal.
 
Jane Monheit of album from "The Heart of The Matter," "Depende De Nos" session by the band of vocals and acoustic instruments. Plump sound and clear bass of acoustic instruments, even listening in 3-pole cable, I was surprised to reproduction force of the natural texture of vocals. But if you change the cable of the 4-pole specification, the more it is difficult is to believe suddenly that you are listening at the same headphones, playing three-dimensional sense of imminent come as took off even many pieces the veil. Only the vertical and horizontal direction of the sound field is spread at once rather than the depth direction, percussion of sound takes shine to Tsubudachi. Vocal sense of resolution mouth increases, the voice of vibrato and breath of expression are more vividly image. Acoustic guitar and accordion, color increases the tone of the piano, the low frequency of the wood-based further increase the depth of the carving. 

 
Why would Oppo Digital not offer a TRRS-to-TRRS cable as a PM-3 option for those who also have the HA-2?
 
Could it be that it doesn't really offer any audible benefits? 
 

 
We have no evidence that the HA-2 offers more power when running with a TRRS-to-TRRS cable to the PM-3.  In my opinion, unless the amp actually produces more power to each channel with balanced output, as is the case with the HA-1 or a portable like the iBasso PB2, there are no audible benefits - and even then, the headphones must be sufficiently inefficient to actually enjoy the greater dynamics and bass control that accompany an increase in power.  If unbalanced operation supplies sufficient power for an efficient headphone, it's unlikely you'll hear any benefit by going to balanced cables with an amp that offers more power when doing so. There's even less likelihood of enjoying audible benefits if the amp offers no increase in power with balanced output vs. unbalanced.
 
For more on my opinion of balanced operation, see: http://tinyurl.com/paxte3t 
 
Mike

 

[alerma]

I am not sure why OPPO doesn't offer a TRRS-TRRS audio cable for PM-3, maybe because these cables can be bought cheap on internet? BTW, OPPO also doesn't offer balanced cables for PM-3... I personally don't think that separated grounds design is a gimmick. The same design is used in ZX2, so there should be a reason. As I heard, the separated grounds design has all advantages of a balanced design except a doubled voltage sweep. You should hear a better sound stage and separation...

 

[gerelmx1986]

  I've found interesting information about HA-2 on OPPO Japanese site. There is a product feature description that seems missing in US variant on US OPPO site. According to the description (Google translated) HA-2 has TRRS output connector and uses separated grounds design, similar to ZX2 and Hifiman. 
 
The original link: http://www.oppodigital.jp/products/headphone-amp/ha-2/
 

[size=15.07px]Stereo headphone output which adopted the GND separate design[/size] Traditional portable audio equipment, deterioration of channel separation could not be avoided due to the commonality of Lch and Rch of GND of the headphone output (ground). Stereo headphone output of HA-2 will be to adopt a design that was completely separate the GND in the left and right up to the jack part of the four-pole type from the amplifier circuit (※), we are held down by thorough deterioration of channel separation . As a result, we have achieved a wide sound field reproduction is not only clearer localization.Also is possible GND separate drive in combination with PM-3, which has become a GND separate design.

※ 3-pole plug of the earphones, there is no hindrance to operate even use our headphones. Earphone of 4-pole plug in the case to take advantage of the GND separate design, please use headphones. Pin assignment, please refer to the following image.

 
The another article in Japanese has a lot of talking in great details about advantages of separated grounds design, see it here (use google translation): http://www.phileweb.com/review/article/201505/13/1626.html
 
In addition the article has some valuable information about internals of HA-2, see below (google translated):
 

 TI's op amp to headphone amplifier "OPA1602", as well as constitute a differential amplifier circuit using a "OPA1662". In addition it has the company's headphone amplifier IC and "TPA6120" and analog amplifier design for mounting a class AB current amplification transistor. By using a part which has been sorted while achieving a compare match to the output stage, and is thoroughly care both power and quality of the output signal.

Hope is not a special model for Oppo japan, you know like sony does sometimes

 

[Smarty-pants]

 
Hope is not a special model for Oppo japan, you know like sony does sometimes

There is no difference between any of the Oppo HA-2 models sold around the world. They are all the same.

 

[Smarty-pants]

 
Why would Oppo Digital not offer a TRRS-to-TRRS cable as a PM-3 option for those who also have the HA-2?
 
Could it be that it doesn't really offer any audible benefits?
 

...or at least not enough of a difference that they would want to promote it as being better?
I haven't heard balanced vs unbalanced in the PM-3, but people like to believe there is a big difference when they do the work
and spend the money to convert over to the balanced setup with the PM-3.
Kind of like cleaning and waxing your car makes it feel like it runs and drives better.
Not trying to mock those who have done it, to each their own and I'm sure it's fun to do these things,
and again gain I haven't heard it both ways, but Oppo's decision not to promote the PM-3 as a balanced capable headphone
has to have some logical basis for being, and I think that negligible difference, or no difference, is probably the answer.

 

[alerma]

At least on their Japanese site OPPO advertises PM-3 as having separated grounds design "providing a clearer localization and wider sound reproduction."
 
 

[size=15.0799999237061px]Adopted GND separate design corresponding to the 4-pole input[/size] Stereo mini-jack end of the PM-3 is adopted GND separate design that separates the left and right of GND (ground) (※). Not only corresponds to the headphone of BTL (balance) drive, it can GND separate drive in combination with HA-2. 4-pole output capable player, it is possible to use a portable headphone amplifier, to improve channel separation, providing a clearer localization and wider sound reproduction.

※ the 3-pole plug of cable use our does not have trouble with the operation. Please use the cable of the 4-pole plug in the case to take advantage of the GND separate design. Pin assignment, please refer to the following image.

 

[gerelmx1986]

There is no difference between any of the Oppo HA-2 models sold around the world. They are all the same.

Glad to know now the tricky part comes into play. I received a balanced audio cable from some Z5's from a canadian head.fier and i gave him for exchange my european smarthphone cable that csme with my XBA-H3's.
 
The balanced cable has two separate TRS plugs, one for right and one for left. so is there an adapter that has two female input jacks TRS and a male TRRS pin to use with my HA-2? you know like those belkin headphone splitters. e.g to convert from two separate connections to one 4-pole

 

[alerma]

  Glad to know now the tricky part comes into play. I received a balanced audio cable from some Z5's from a canadian head.fier and i gave him for exchange my european smarthphone cable that csme with my XBA-H3's.
 
The balanced cable has two separate TRS plugs, one for right and one for left. so is there an adapter that has two female input jacks TRS and a male TRRS pin to use with my HA-2? you know like those belkin headphone splitters. e.g to convert from two separate connections to one 4-pole

 
I also would like to know if such an adapter exists. I saw some splitters from TRRS male into 2 TRS females, one for stereo and another one for mic, but I believe they have different wiring.

 

[miceblue]

How can you have more than 1 ground reference in a circuit anyway?

 

[Neo Zuko]

Oppo told me that the extra ground in the headphones and amps was there to tick that marketing box, because they could, because the competition does it. Sound quality doesn't seem to be a real issue with the older method.