So, the X10 is a pain to use without an amp with low output impedance. Actually iPhone 4/4S has a decently low output impedance and its performance can put some of those external amps and DACs (Fiios included) to shame. But it costs SGD$500 (16GB) with a plan (the one I'm planning to get), does not have a 16:9 screen, and cannot play Pokemon Online. So screw it, Android FTW.
With my recontract still a while away, I am relying on my PSP for video duty on my daily commute. The amp's performance is quite acceptable, but with a high output impedance it messes with the X10's sound. I need an amp, small enough and just decent enough. Fiio E5 comes to mind.
Why E5 and not E6 or E11? Well, it's slightly cheaper than the E6 (USD$20 before shipping now, actually it once hit $15 before shipping but I didn't buy it then although I was tempted to, ため息。), but more importantly, according to NwAvGuy, E6 and E11 both have a nasty power supply noise (does it count as power supply if the switching power supply is inside the amp chip itself?) at high magnitude and frequency. From personal experience, ultrasonic noise can show up as whine or hiss in the audible frequencies depending on your setup, which probably explains why some people complained of hiss with certain earphones. And with X10 having a sensitivity of 110dB/mW, this is not a chance I'm going to take.
But then, in a sudden twist of events, I became the owner of an E11, hours after I received the E5 in the mail.
And then, I decided to just also measure both amps the way I usually do. So this review will have two parts - Xonar DX Edition, where I test them with Xonar DX's output at a high volume setting (the usual way), and PSP Edition, where I test it in conditions closer to real life.
And then, I decided to put the PSP Edition in a separate post and make Xonar DX Edition the main one, in order to make things less messy because I don't know how to do multi-page posts in blogger so I can do it the way professional review sites do it.
Arta + Xonar DX loopback results
This review is also the first time I use Arta to measure THD+N @ 20Hz, 1kHz and 10kHz to supplement RMAA's results. THD+N is more important than THD, because often the output level can be reduced to result in lower THD at the expense of more noise; THD+N measures both THD and noise so a good balanced is needed. And then 20Hz and 10kHz, because 1kHz doesn't tell the whole story - what if the power supply is too weak to produce 20Hz, for example.
(RMAA does measure TDH+N @ 1kHz, but it is only visible in the HTML report.)
As with all measurements, we need to know the limits of the measuring equipment so that we know if a bad result is due to bottleneck by the equipment being measured or the equipment measuring.
These results are measured @ -3.7dB:
As you can see, Xonar DX's 20Hz performance is not as good as its others. Not too shabby,but 0.0021% is rather average, which means the DX may bottleneck some measured equipments' performance. Also the 0.030% TDH+N is suspicious, but with no way to verify it I can only accept it. It is going to limit the TDH+N 20Hz measurements big time.
The noise near 30kHz, this is noise from where I live and it shows up on the speakers when it is high enough.
The measuring, Xonar DX Edition
Xonar DX volume: Max, resulting in 1.69Vrms
E5: Amp volume @ max, Xonar DX's output @ 50%
E11 high: Gain switch is set to low, amp overall gain @ 1
E11 low: Gain switch @ low, amp overall gain @ -2.3dB
E5 suffers from input clipping at a rather low voltage. So to be safe I tested with Xonar DX's output @ 50% and set the E5 to max, resulting in -7.3 left / -7.1dB right at Xonar DX's input.
At low power setting and 33Ω load, the E11 clips rather early with distortion rising sharply after 1.3Vrms. So instead of overall gain @ 1, the volume control is adjusted such that overall gain is -2.3dB, resulting in 1.3Vrms
The results, Xonar DX Edition
|Unloaded||E5||E11 high||E11 low|
|33Ω load||E5||E11 high||E11 low|
Results discussion (Xonar DX Edition) - E5
For such a small amp, it does not lose much performance when driving a 33Ω load compared to when unloaded (1.5 times is around 3dB higher). While that is commendable, that is because the unloaded performance of the E5 is not good to start with. 0.014% @ 10kHz and a horrible 0.23% @ 20Hz puts it slightly below "marginally usable". (So should I call it marginally fail?) So loaded performance, which is similar to unloaded, is also "marginally fail".
That said, the THD@1kHz is pretty good for its size and price, and if this number, unloaded and loaded, is indicative of an amp's general performance, then I believe there are many worse amps out there. Much, much worse and way, way more expensive.
Results discussion (Xonar DX Edition) - E11
I won't say that it is a high-end amp, for I have seen desktop amps that do 0.001% THD @ 1kHz, but for its price and portability, the E11 is one heck of a performer. In high power mode, with a 33Ω load, it does 0.003% THD @ 1kHz. Good players/phones have around that much distortion, maybe a little bit better, without driving a load. So you won't be losing much sound quality with this amp.
As a preamp (i.e. unloaded), here is where it does wonders for its price/size. All numbers are around the same as without the E11 in the loopback chain, some numbers slightly better, some slightly worse, and all excellent. Except the 20Hz which is due to DX bottlenecking so the E11 probably does better.
It performs better than cMoyBB, if you want to know. And it's not really that much more expensive either... in fact after considering the casing, the li-ion battery, charging circuit, and the cables, E11 is cheaper than cMoyBB. Oh well.
Performance @ low power mode is slightly worse than high power, but the amount of degradation is acceptable in exchange for longer runtime. However the output clips way too early when loadede. Low-sensitivity and high-impedance headphones will want to stay away from this mode. In my opinion, the battery life of such amplifiers is very long anyway, so just stay with high power.
E5 input clipping
If you have read NwAvGuy's review of E5, the clipping threshold was measured to be 760mVrms. Well, clipping is one thing, but distortion will also be rising as the limit is approached.
0.0070% of E5 max, Xonar @ 70% vs 0.0075% of E5 gain 1, Xonar @ 50%.
While distortion is indeed higher with higher input levels, the difference is minimal. So it'll be safe as long as input level is within or below this range. Which is the case for majority of portable devices @ max volume. So you'd probably want to operate your player @ near max volume, so you will get less quantization error and noise. But not high enough to make the player clip though.