I've been holding back from writing a review because it is important to live with a mobile product for at least a month before espousing its virtues. At least I think it is.
I'm sure there are many internal technical merits to this dac/amp that others can cover in more detail, but I don't care about the internal components as much as I do about it doing its job so I'm going to recount my month's experience with this dac/amp.
Who am I? Just another audio fan. I aim for an audio reproduction that will match what the recording's producer perceived. Clearly not possible, but it is a goal none the less. This means that I will eq any system to get it close to perceptually flat. For my home stereo this meant considering room reverb and nulls more than digital eq, but for headphones there is little I can do in terms of room acoustics though I have dabbled in stuffing headphones to aid eq. IEMS however permit no mods except tips for a good seal, so parametric eq processing has become my friend and graphic eq otherwise.
Where/when do I use this amp? I use it at my desk at work all day during the week for 4 to 8 hours (sometimes more). I use it when going to bed if I want to listen to music to help me relax and fall asleep (maybe an hour). I use it when the baby is asleep at home. Where I once used to use headphones on public transportation, I no longer use public transportation so I can't comment on the impact there. That said it fits fine in any of my paniers as I bike to/from work.
How do I use the dac/amp? At my desk I use Winamp and EqualizerAPO on Windows 7 with the PHA-3 set to 24bit/192kHz giving the eq lots of room to manipulate the source and have little affect on the final output in terms of dynamics. Everywhere else I mostly use the Onkyo audio player because of the greatly customizable eq. I would consider a player with a parametric eq, but I've only found Neutron to have it and that app has been a pain to try out so I haven't bothered any more with it.
Physically I find the amp large, but it complements the size of my Note 3 phone that I use as a DAP. With extended play time the amp is warm to the touch. The aluminum casing was clearly a necessary heatsink part of the design.
Recharging via various usb chargers(500ma to 2400ma) is fine except the Samsung charger that outputs 5.3v that the PHA-3 refuses to work with so I'm guessing Sony put some over-voltage protection into the design to keep the batteries from being over-charged and having a shorter life span. As noted in the manual charging time can be as short as 6 hours, but only with a high current charger.
When I first got the PHA-3 I plugged in my Beyer DT880 600ohm at home because it was what I had nearby and used an un-eq'd feed from my pc. It drove them fine on high-gain, but the sound was exactly like the frequency-response of the headphone. This is great for the amp, not so great for the headphone as they have a big bump up around 8kHz that bothers me, so I headed for the eq. While keeping the fatiguing part of the frequency response in check I also decided to bump up the sub-bass. Now the DT880 has a low sensitivity and high impedance which combined with a -12db pre-amp level rendered the DT880 just barely loud enough to constitute my normal engaged listening level. Turning the volume dial on the PHA-3 past 3-o'clock made the phones bottom out. Distortion in the driver was clear from the sounds of the diaphragm hitting its excursion limit and breaking up. This happens with the same settings on my tube amp, but at a slightly higher listening level. Likely this is due to the tubes having a sub-bass roll-off that the PHA-3 does not have. I do not use the DT880 to get my sub-bass fix so not a big deal, but the experience had me wondering if I was missing other rolled-off sound elsewhere.
Next on my trial list was the MDR-1R. I didn't have the T1, SZ2000, or Westone 4 on hand, and I wanted volume and couldn't hold myself back from using the PHA-3. The 1R I had not used in some time as the closed design leaves something to be desired in terms of sound stage. The end result is that I have new found appreciation for these phones. The amp can control them so well that with a really small amount of eq I got the response that I was looking for and sub-bass. So much so that I thought they were in competition with the SZ2000. Later on when I did have the SZ2000 hooked up there was no contest, but the point is that the PHA-3 happily took the +10db at 16Hz Q0.25 and the 1R responded with audible reproduction of the frequency. With music the 1R sounded good albeit closed and less clear than I'm used to with the T1, but good none the less and with fewer/minimal higher frequency eq tweaks than any other headphone I have.
By the time Monday rolled around I was really looking forward to continuing the experimentation. The T1 was first and I was noticing some better sub-bass control, but nothing stellar so I just kept listening. The next day I wanted more sub-bass out of the T1 for electro-tango, but I just couldn't get the PHA-3 to give me the same volume and bass control that I felt I could get with my vacuum tube amp + m-audio fast track i/o DAC/ADC. After more comparison I was staring to feel let down a bit in that they both had pros and cons. The PHA-3 had good sub-bass control, but not as good volume whereas the tube amp had the volume, but rolled off sub-bass. I was thinking that a high-power dedicated desktop amp was in my future and the PHA-3 would become my home/mobile dac/amp. Scouring the web for any/all impressions on the T1 and PHA-3 I found several comments on how the balanced output was really fantastic; So I decided to re-terminate the T1 with a 4-pin mini-XLR and make an adapter to make use of the balanced output. The results were fantastic. Volume was there in spades. High-gain was no longer needed. I was enjoying the T1 more than ever. Micro-details were clear and dynamics effortless. Weeks later, I miss the glow of the tube amp on my desk, but it was brought home because I had no more use for it at work. Much time was spent with the T1 tweaking the eq. It amazed me how well the DAC/amp could drive the T1 with whatever large eq changes I made and not loose information. I have finally settled on two parametric eq profiles for the T1. One for regular listening and one with extra sub-bass for demanding tracks that have acoustic instruments and electronic sub-bass such as electro-tango. The fact that I can take the pre-level down 16db so that the sub-bass can stay at line level and then further drop some other levels another 6db and still hear the dynamics clearly speaks volumes to me about Sony's DAC and amp implementation. I love the resolution of the T1 and in 24bit processing, it does not feel as if I'm missing much with the PHA-3 and eq. I couldn't do that with the 24bit m-audio dac and get the same volume/control/detail out of the tube amp. The m-audio DAC's headphone out was just too weak to drive the T1 with such an eq.
I've now been slowly converting my headphones to balanced cabling. The Westone 4 is efficient, sometime annoyingly so, but I wanted to see if the conversion helped at all and it did. I just got them back from being re-cabled and was even more worried that maybe I could now hear more about what was going on in the building's power fluctuations than ever, hiss abound. With the PHA-3 that didn't happen. Silence in lo-gain and silence in high-gain. On high-gain If I have no music playing(would be deafening otherwise) I can start to hear the noise floor with the volume set to a little past 1-o'clock. Everything sounds tighter and better controlled. I haven't yet converted the SZ2000 to balanced as I use it for more sub-bass heavy music occasionally, but it is on my list. It is too bad that the 1R has a single ended plug in the headphone as I was hoping to convert them to balanced, but I'm not about to go get the MDR-1A.
The hardest review for me to write is one that finds little or nothing wrong with a product. I find nothing wrong with the PHA-3, it just works as advertised, no weakness, no roll-off, no emphasis, it just does its job quietly and admirably.
It feels as if the character of the rest of the audio chain is very clearly on display. With digital in, the chain isn't very long, so headphone differences come to the fore.
If anything it has peaked my interest in balanced headphones.
Looking forward to a decade or more of use.