[qsk78]

Would I be better off going with a portable amp/dac like the HA-2 with my Note 4 or getting a DAP like the iBasso DX50 for my IEM's?

I had the DX50 / DX90 in the past. OPPO HA-2 will outperform both. 

 

[NZtechfreak]

Is this the one? http://www.ttvjaudio.com/Nightscout_TTVJ_Micro_USB_to_Micro_USB_Cable_p/ttvj000001.htm



What phone are you using? Do you have the short or long? It says the [COLOR=FF0000]red[/COLOR] end is for the phone. I didn't know OTG cables had device specific ends. I just grabbed the stock cable and plugged it in at random when I tried the HA-2 last night in the store.

Yes, that is the one (short).

For a cable to be recognised as an OTG cable, and therefore to trigger host mode in the handset, the pins are altered (I forget the specifics, one pin is shorted, or something like that). I think they have done that to both terminations in the Oppo cable, as I spent a minute looking for a way to discern the end to connect to the phone, couldn't find any indication and just randomly plugged it in.

 

[NZtechfreak]

Would I be better off going with a portable amp/dac like the HA-2 with my Note 4 or getting a DAP like the iBasso DX50 for my IEM's?

I prefer using my phone as a transport, but you can argue either way depending on your use case. Things I like about using a smartphone this way, rather than carrying a separate DAP: no hokey UI, ability to use apps like Spotify/Tidal/DS Audio (for my NAS), ability to use with my laptop and work computer, not having to concern myself with what DAC and implementation a manufacturer has used when it comes time to buy my next phone (although granted a DAP will also do that for you).

 

[Gr8Desire]

That's pretty strange. My 88 dB SPL/mW, 669-ohm AKG K240 Monitor headphone gets plenty loud for me with the HA-2 on high gain, maximum digital volume, and level 4 analogue volume as a PC USB soundcard as well as a USB DAC with my iPhone with some of my quietest music tracks. I'd say the K240 Monitor is a tougher load for the HA-2 compared to the HE-560 because as I mentioned earlier, the HA-2 is voltage limited due to the battery. Analogue volume level 5 is too loud for me in a quiet room and volume 2.5 is about my comfortable listening volume level.

Low gain, maximum digital volume, level 5 analogue volume is still pretty loud for me and for not-as-quiet music, I would probably never use high gain.

Spoiler: Math, for the fun of it

As per OPPO's official specifications:
https://www.oppodigital.com/headphone-amplifier-ha-2/headphone-amplifier-HA-2-Features.aspx
300 mW into 16 Ohm, or 2.19 Vrms voltage output, 136.93 mA current output
220 mW into 32 Ohm, or 2.65 Vrms, 82.91 mA current output
30 mW into 300 Ohm, or 3 Vrms voltage output, 10 mA current output

So 136.93 mA is the maximum current the HA-2 can deliver, and 3 Vrms is the maximum voltage the HA-2 can deliver



AKG K240 Monitor's official sensitivity rating
88 dB SPL @ 1 mW

My measured impedance rating: 669-Ohms

P = I * V
P = Vrms^2 / R
0.001 W = Vrms^2 / 669-ohms
0.8179 = Vrms

0.001 W = 0.8179 Vrms * I
I = 1.22 mA

Voltage limited to 3 Vrms, so how much maximum power can be outputted into a 669-ohm load?
P = (3 Vrms)^2 / 669-ohms = 0.01345 W or 13.45 mW

13.45 mW = 1 mW * 2^x
13.45 = 2^x
log(13.34) = x * log(2)
x = 3.74

88 dB SPL + 3 dB SPL * 3.74 = 99.22 dB SPL maximum loudness


Remember that the HA-2 can get the HE-560 to 108 dB SPL. So yes, the K240 Monitor is a more difficult headphone for the HA-2 to drive.

Thanks for the detail.  Are these are DC calculations?

I get the impression something is missing.   The HE-6 planar headphones have DC resistance of 50 Ω yet most people seem happiest with speaker amps.  

In there some type of AC impedance change with planar phones that means they need to be amped differently?

Or do they need higher voltage?  Some portable headphone amps tout output of 7V or higher. 



 

 

[TheChillburger]

My HA-2 drives my Alpha Dogs, HE400i, and HD600 well beyond comfortable listening levels. What a beastly little device. Going to be nice to not have to lug my O2 / ODAC stack to work

 

[Uberzone]

Maybe someone compared HA-2 vs Herus?

 

[rschoi75]

I had a great listening session last night with this set up here: 
iPhone 6 > Tidal > Oppo HA-2 > Noble K10
 
It makes a nice and tidy little stack with the iphone 6. Dimensions are pretty close, but I think it would do better with an iphone 5/5s or touch 5g. 
 
The music coming out of this combo sounds on par with an Astell & Kern AK100ii + K10's. Clean, crisp, airy, and tight. Like a brisk morning walk after a night of rain. I love it. 
Excellent Hi-Fi sound for a Mid-Fi price (the amp, not the ciem's). I'm seriously tempted to sell the AK100ii that I own, and go out and buy an ipod touch 5g so that I can free up my phone for texts/calls, and pocket the cash difference in price. 
 
Very nice job Oppo. I think you guys have an outstanding product here. 
 

 

[money4me247]

I prefer using my phone as a transport, but you can argue either way depending on your use case. Things I like about using a smartphone this way, rather than carrying a separate DAP: no hokey UI, ability to use apps like Spotify/Tidal/DS Audio (for my NAS), ability to use with my laptop and work computer, not having to concern myself with what DAC and implementation a manufacturer has used when it comes time to buy my next phone (although granted a DAP will also do that for you).

+1. makes so much more sense to me to get a portable dac/amp rather than a dap that will be out of date in an year or so. so much more flexible.

 

[money4me247]

  Maybe someone compared HA-2 vs Herus?

I have both the Herus & HA-2 and I just recently updated my Oppo PM-3 review w/ impressions (currently in progress though, so may be subject to change). Full PM-3 review in my signature, Ctrl+F to "Portable amp/dac" to just skip down to the Herus and HA-2.
 

Spoiler: quoted portion of the review

[size=14.9499998092651px]Portable Amp/Dacs: I tested the PM-3 with the Resonessence Herus and Oppo HA-2 individually on my S5 and laptop. Greatly enjoyed both pairings and they were adequate to drive the PM-3 without any noticeable clipping. Improved detail resolution and sound stage with both the Herus and HA-2. Precision of the imaging is stellar on both portable devices. The Herus has a brighter presentation than the rest of the dacs I own. This pairing can help improve the treble clarity and sharpness of the PM-3 without any excessive edginess. The Herus would be a good match if the treble presentation is too smooth or recessed for your personal tastes or if you like to subtly dial down the warmth in the sound signature. The PM-3's tuning and presentation prevents the sound from ever getting piercing or strident even with a bright dac. Link to the head-fi Herus thread here. I am still getting familiar with the HA-2; may comment in more detail on its sound later. Initial impressions are extremely positive and I feel that it is a great pairing for the PM-3. So far, the HA-2 does not appear to significantly alter the PM-3's overall sound signature to my ears, but it does improved the overall clarity throughout the frequency response. I immediately noticed improved sub-bass quality, deeper lower frequency extension, and better defined solid bass impact with the HA-2. The HA-2 is more revealing of subtle micro-details in the texture and improved the overall tonality with a realistic weight and presence to the notes. The bass boost feature provides an extremely clean bass 5dB boost frequencies below 100 Hz that tapers to 500 Hz. There is no muddiness or bleeding into the rest of the frequency response. You actually cannot hear a difference in the sound at all with bass boost on/off if you play music that does not have any notes below 500 Hz. I normally have the HA-2 set on low gain, no bass boost, volume pot at 1-2 out of 5 with the S5's volume maxed out. The HA-2 can even drive my HE-560 without any clipping to my preferred listening levels (maxed out volume on the S5 with analog volume pot at 2-3 out of 5 on high gain). Do note that precise volume-matching was a lot harder to do here with the Herus on the S5 having large volume steps, while the HA-2 allows extremely precise fine-tuning of volume levels with the combination of the Sabre dac chip's bit-perfect internal digital volume control and analog volume pot. There is no digital signal processor in the HA-2 and the bass boost is performed by pure analog audio circuits for a clean signal path. Link for HA-2 head-fi thread here.[/size]

 

[miceblue]

Does the Apple USB input NOT draw power so that it will not be a problem for iPads etc with restricted power out of the USB.
I don't use Apple anything, but using the internal battery would be good for insuring clean power to the DAC/amp.

If this doesn't work the way I hope, what is the real differences between the two US inputs?

Is this the one? http://www.ttvjaudio.com/Nightscout_TTVJ_Micro_USB_to_Micro_USB_Cable_p/ttvj000001.htm



What phone are you using? Do you have the short or long? It says the [COLOR=FF0000]red[/COLOR] end is for the phone. I didn't know OTG cables had device specific ends. I just grabbed the stock cable and plugged it in at random when I tried the HA-2 last night in the store.

I received confirmation from OPPO Digital about these things:

When connected to a PC, the HA-2 draws power from the PC. The power is used to operate the circuits and charge the battery. You will see the charging indicators blink if the battery is not already fully charged.

When connected to an Android device using the supplied USB Micro B cable, the HA-2 does not draw power from the mobile device. If it is connected using a common OTG dongle, the HA-2 will not know that it is connected to a mobile device and will try to draw power.

iOS devices are special because Apple has a protocol called iAP for the iOS device and its peripherals to negotiate everything, including power consumption, charging current and audio data. The HA-2 does not draw power from the iOS device. It can supply power if the power bank function is turned on.

There is no ground galvanization or isolation (in the strict sense) between the HA-2 and the source device. However the ground from the input ports are considered "power ground", and there are design measures taken to treat power ground, digital ground and analog ground properly in order to avoid problems caused by improper ground current or by interference.



The supplied USB Micro B cable is the key for the HA-2 to know that it is connected to an Android device. The cable is basically two common OTG dongles connected back to back with a special resistor on the detection line for identification. When this cable is used, the HA-2 does not draw power from the Android device.

If the HA-2 is connected to a computer or an Android device using regular OTG dongle, it will draw power from the source device. The charging circuit inside the HA-2 will decide how much power it can draw by gradually stepping up the current and monitoring the voltage. If the voltage drops too much it will back off to a lower charging current. Of course if there is no power to draw (such as in the case of the Sony Walkman connection), the HA-2 will use its own battery power.

Thanks for the detail.  Are these are DC calculations?

[COLOR=A52A2A]I get the impression something is missing.[/COLOR]   The HE-6 planar headphones have DC resistance of 50 Ω yet most people seem happiest with speaker amps.  

In there some type of AC impedance change with planar phones that means they need to be amped differently?

Or do they need higher voltage?  Some portable headphone amps tout output of 7V or higher. 

I'm guessing they're DC calculations, yeah.

The HE-6 is a different beast all together. I don't expect the HA-2 to drive them well at all because they legitimately require a powerful amplifier that, until recently, most headphone amps didn't deliver more than 1 W of power output. The HE-6 is an extremely inefficient headphone, probably the least efficient one I've ever seen and requires 19.69 mW of power (1.018 Vrms, 19.34 mA) at 53-ohms to reach 90 dB SPL according to Innerfidelity's measurements, 1.26 W (8.17 Vrms, 144.51 mA) to reach 108 dB SPL.

Planar magnetic headphones are purely resistive because they contain no inductive elements unlike a cone driver. I don't think there's some AC stuff we need to worry about here....AC is far more dangerous to work with than DC. Only in an AC-powered DAC and/or amplifier would we need to worry about AC, but since the HA-2 is run on batteries, that only outputs DC.

What portable amps output 7 V or higher? I'm guessing it's a balanced amplifier. The FiiO E12 handles up to < 8 Vp-p, or 5.302 Vrms, which quite frankly already outputs more voltage through a singled-ended connection than any of Sony's portable balanced headphone amps.

As for speaker amps, I don't buy that argument. I've listened to the HE-4 on normal headphone amps as well as Emotiva speaker amps and although the Emotivas did indeed sound better, I also heard the same benefits on a really efficient, easy to drive, V-MODA M-100. I think any benefit from a speaker amp would be from a better amplifier design, not the power output necessarily. I've already mentioned that I heard no appreciable difference between my Geek Out 450 (2.68 Vrms) and 1000 (4.272 Vrms) using the HE-560 and I got plenty of volume wiggle room with the GO450 and I'd expect that for the HA-2 too since it outputs a similar voltage level.

If anything, the speaker amp made the listening experience worse overall because it has so much power output that it made the volume knob pretty much useless to use even with 50% digital volume and losing bit depth through the DAC, as is to be expected of any powerful amplifier. The owner of the speaker amp eventually sold it exactly because of that after reading numerous statements around hi-fi websites saying that speaker amps really make planar magnetic headphones "shine."

Anyway, this is getting a bit off topic. XD

 

[NZtechfreak]

Interesting comment about volume control in the speaker amp scenario, can't say that's ever been a problem for my 6. What was the setup? Sounds poor if using volume control in the digital domain like that. Even when I used Merak monoblocks at 200W per channel I didn't have that problem.

Thanks for the info from Oppo on their bundled OTG cable, interesting approach, if only the cable wasn't so impractical!

 

[swimmintunes]

Received my HA-2 yesterday but have only had time to try it with my iPhone 6 and Senn Momentums over ears. Initial impression was very positive. I've never been a fan of the iPhone's music capabilities and have always sided with a separate DAP like, IBasso DX100, 50 or the new Cowan which is on my wish list. I have to say that my first few songs listened to (all 320 MP3) sounded pretty damn good. Decent across the spectrum with increased imaging and seperation.

I'll be pairing with the IBasso DAPs this weekend but will hold off on all reviews until I get my custom 1964 ADEL A12s in the next week or two.

 

[argustimewas]

 I received my HA-2 today.  Before I purchased it, I emailed Oppo and they said it would be compatible with my iPod Classic 160 GB firmware 2.0.4 and I could bypass the DAC in the iPod using the USB connection.  wood1030 also confirmed that his iPod with that same firmware worked in an earlier post on page 37 of this thread, and he posted a picture on that page showing the HA-2 as recognized in the Settings>About screen from the iPod.  I tried the same thing and it did not work on my iPod.  I don't know why his worked and mine didn't, maybe he has a different model with a different serial number.  My serial is MC297LL.  Also, I can't get the fourth click spot in the Settings>About mode to show up on my iPod.  Mine has only three spots. 

This is identical to my experience.
 
I'd appreciate any advice on how to get my 7th Gen iPod Classic to be able to make use of the DAC in the HA-2 please? I don't think it's a cable problem as the same cable allows me to use my iPhone 4 running iOS 7 into the HA-2 DAC section.

 

[Uberzone]

  I have both the Herus & HA-2 and I just recently updated my Oppo PM-3 review w/ impressions (currently in progress though, so may be subject to change). Full PM-3 review in my signature, Ctrl+F to "Portable amp/dac" to just skip down to the Herus and HA-2.
 

Spoiler: quoted portion of the review

[size=14.9499998092651px]Portable Amp/Dacs: I tested the PM-3 with the Resonessence Herus and Oppo HA-2 individually on my S5 and laptop. Greatly enjoyed both pairings and they were adequate to drive the PM-3 without any noticeable clipping. Improved detail resolution and sound stage with both the Herus and HA-2. Precision of the imaging is stellar on both portable devices. The Herus has a brighter presentation than the rest of the dacs I own. This pairing can help improve the treble clarity and sharpness of the PM-3 without any excessive edginess. The Herus would be a good match if the treble presentation is too smooth or recessed for your personal tastes or if you like to subtly dial down the warmth in the sound signature. The PM-3's tuning and presentation prevents the sound from ever getting piercing or strident even with a bright dac. Link to the head-fi Herus thread here. I am still getting familiar with the HA-2; may comment in more detail on its sound later. Initial impressions are extremely positive and I feel that it is a great pairing for the PM-3. So far, the HA-2 does not appear to significantly alter the PM-3's overall sound signature to my ears, but it does improved the overall clarity throughout the frequency response. I immediately noticed improved sub-bass quality, deeper lower frequency extension, and better defined solid bass impact with the HA-2. The HA-2 is more revealing of subtle micro-details in the texture and improved the overall tonality with a realistic weight and presence to the notes. The bass boost feature provides an extremely clean bass 5dB boost frequencies below 100 Hz that tapers to 500 Hz. There is no muddiness or bleeding into the rest of the frequency response. You actually cannot hear a difference in the sound at all with bass boost on/off if you play music that does not have any notes below 500 Hz. I normally have the HA-2 set on low gain, no bass boost, volume pot at 1-2 out of 5 with the S5's volume maxed out. The HA-2 can even drive my HE-560 without any clipping to my preferred listening levels (maxed out volume on the S5 with analog volume pot at 2-3 out of 5 on high gain). Do note that precise volume-matching was a lot harder to do here with the Herus on the S5 having large volume steps, while the HA-2 allows extremely precise fine-tuning of volume levels with the combination of the Sabre dac chip's bit-perfect internal digital volume control and analog volume pot. There is no digital signal processor in the HA-2 and the bass boost is performed by pure analog audio circuits for a clean signal path. Link for HA-2 head-fi thread here.[/size]

Big thank you mate. If you choose both devices exclusively for laptop, would you choose?

 

[money4me247]

  Big thank you mate. If you choose both devices exclusively for laptop, would you choose?

for exclusive laptop usage, I would actually go in a completely different direction and get a desktop dac with its own power supply. The draw of both the Herus and HA-2 in my mind is their portability. To achieve the smaller portable size will require certain sacrifices in the design, and I imagine it should be possible to find a better performing desktop dac at that price range. Fro example, the Bifrost (without USB or Uber) is just $350. Do note that from my experience, scaling up with dacs do end up with pretty extreme diminishing returns. Will depend on your source and headphones how much improvement you notice, so I usually spending your budget into nicer headphones first until you get into the flagship territory.