FiiO E5 Headphone Amp

INTRO (updated 4/7): The little FiiO E5 typically sells for under $20 and is so small you barely notice it. It’s “Apple-Shuffle-size” small. And, despite the ultra slim metal package, it has a Li-Ion rechargeable battery tucked inside, volume control, and selectable bass boost EQ. They even wisely made it rechargeable from a standard mini-USB cable so you probably have a cable laying around already if you lose the one that comes with it.

FOOD INGREDIENTS: Ever watched any of those “chef shows” on TV? They give a team of chefs a simple assortment of ingredients and challenge them to make something amazing. The best chefs take common everyday items and create really tasty mouth watering entrees. That’s what FiiO has done here. This is in sharp contrast to certain “boutique” audiophile companies that take high-end exotic ingredients and combine them in ways that don’t taste very good. The difference, in my opinion, is engineering talent and resources.

To put this another way, a good French chef can do more with a few eggs, cheese, butter and a piece of bread than a bad chef can do with $500 worth of exotic ingredients. What good is including exotic ingredients if the entrée tastes awful? FiiO seems like they have a French chef on staff able to transform inexpensive parts into something that’s relatively impressive.

CLIP IT ON: Like the Sansa Clip+ (see my review) it has a built in clip (sexy metal even!) to help with cable management. So you can have your player in your pocket, and the E5 clipped to your shirt, or whatever might work.

OTHER FEATURES: For the price, the E5 impressed me as being relatively well designed. Here’s a link to the features & specs.

OPERATION: It has a small power button, EQ switch, and a volume up/down “rocker” switch. The volume steps are impressively fine with no big jumps and you can hold down the rocker to steadily increase or decrease the volume easily. You can also use it while it’s charging or just leave it plugged into USB power. On my PC I didn’t hear any extra noise using it on the wimpy headphone output while charging it from a USB port on the same PC. There’s a 3.5mm input and a 3.5mm output jack, the mini-USB charging port, and that’s about it. It comes with all the necessary cables. The LED indicates charge status when it’s re-charging. There are plenty of volume steps so you don’t find yourself wanting for finer resolution.

BASS EQ: The bass EQ subjectively is fairly pleasant, relatively subtle, and particularly welcome with headphones that have flat bass response (i.e. those from Etymotic, RE-1’s, etc.). With bass shy headphones it adds a bit of of “heft” without creating any boom. The curve is shown in the Tech Section but it’s about a 3 dB boost centered at 80 hz.

HISS & NOISE: For such an inexpensive amp, it’s impressively quiet. It doesn’t have much noise of it’s own. Even with my ultra sensitive Ultimate Ears SuperFi 5 Pro’s, the hiss at full volume with no input is barely noticeable. It will, like any amp, boost whatever noise your source device has. See my article on headphone amps.

SUBJECTIVE SOUND (updated 3/21): The E5 sounded impressively good for its size and price. It’s clean, clear, plays plenty loud, and has no issue with low impedance, high impedance or balanced armature headphones. I had no complaints with the sound.

QUALITY CONTROL? My E5 sample has a slightly audible 3.8 dB channel imbalance but only with the bass EQ off. And it’s relatively constant regardless of the E5’s volume setting. Many other E5 owners have confirmed this is not normal. So apparently I got a slightly defective one.

MEASUREMENT SUMMARY: The good news is the maximum output level, output impedance, distortion, and most everything else was amazing for a such a small inexpensive amplifier. The frequency response was –3 dB at 20 hz which isn’t likely to be a problem but isn’t as flat as say the Sansa Clip+ either. And the noise was a few dB higher than I would have liked to see but still respectably low at around –88 dB. The distortion also climbs at very low frequencies but this isn’t likely to be audible as human hearing is not very sensitive to deep bass distortion.

BOTTOM LINE: This a respectable little amp for the size and price. It’s surprisingly well designed, well made and it performs much better than I expected. To put it in perspective, this little $20 amp easily outperforms the amp in the $130 NuForce uDAC-2 in several respects. It has a much lower output impedance, lower overall distortion across most of the audio spectrum and higher output into low impedances. The lower output impedance, in particular, allows it to deliver much better performance with IEMs that use a balanced armature, multi-driver, or similar technology (i.e. Shure, Etymotic, Ultimate Ears, Westone, etc.).

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TECH SECTION (optional reading for more details):

THD & REFERENCE LEVEL: With approximately a 200 mV RMS input (which just about any source should be able to provide), I adjusted the E5’s volume control for 400 mV of output (a gain of “2X”) as this should approximate real world use. With a 15 ohm resistive load, here’s the result:

The distortion of 0.01% is quite good. By comparison, for example, the NuForce uDAC-2 measures about 0.05% on this same test with the same load. What’s really not so good is the 3.9 dB of channel imbalance. This isn’t a “tracking” problem as it’s essentially the same at any volume setting. It’s just one channel has nearly 4 dB more gain than the other but, interestingly, if you turn the bass EQ switch on, it goes away (the channels are balanced). To measure the output impedance, here’s the same set up with no load. The voltage in Channel A went from 401 mV to 420 mV and doing the math, that’s a very impressive 0.7 ohms—that’s even better than I measured with the Sansa Clip+ and I thought it was impressive:

MAXIMUM GAIN & OUTPUT: Here’s the E5 with its volume at maximum. I raised the input voltage until it was close, but not yet clipping. Here, even with 1.27 volts of output into 15 ohms—over 100 mW of output and the THD is still under 0.02%! This is very impressive. And 100 mW is a very impressive output level. This is about twice what the NuForce uDAC-2 could manage into the same load. Note also, this is referenced to the input voltage. So the maximum gain of the E5 is 8.5 dB in one channel and 4.6 dB in the other. I didn’t bother testing into a higher impedance load, because with the 0.7 output impedance it makes little difference. It always starts clipping around 1.3 volts RMS.

INPUT CLIPPING THRESHOLD: To measure how much signal you can drive the E5 with, I gradually raised the input voltage until clipping was detected with the E5’s volume turned down. The answer is a lot! it didn’t start to have a problem until around 760 mV RMS:

THD SWEEP: Here’s the THD swept versus frequency for both channels. The lower traces (red and yellow) are with no load. The upper traces (blue and gray) are with a 15 ohm load. The distortion rises dramatically at lower frequencies and barely at high frequencies. It hits around 0.5% at around 25 hz. Fortunately, humans are rather insensitive to low frequency distortion. Some studies have found even 5% THD below 100 hz is hard to detect. That’s a good thing because most transducers (speaker or headphones) tend to have rather large amounts of low frequency THD at higher volumes. So the midrange and high frequency performance here is excellent, the deepest bass is a bit disappointing but likely not an audible problem:

NOISE: Here’s the “worst case” noise with the E5’s volume at maximum and no input. It’s 1 – 3 dB better and lower volume settings. This is acceptable noise and similar to many portable players and the Behringer UCA202. The NuForce uDAC-2 is significantly quieter.

IMD: Here’s the SMPTE IMD at 400 mV out into 15 ohms. It’s very clean:

FREQUENCY RESPONSE: Here’s the frequency response with various loads. Note the divisions are only 0.5 dB. The –3 dB point is 20 hz. Or, put another way, the E5 is +/- 1.5 dB from 20 hz to 20 Khz which many would argue is “flat enough”. I would have liked to see a bit less low frequency roll off, but this isn’t bad at all as it’s only down 1.5 dB at 30 hz. Interestingly it doesn’t seem to be caused by an output capacitor because the roll off doesn’t change with loading:

 

LOW FREQUENCY EQ OPTION (added 4/7): Below in red is the response (starting at 20 hz instead of 10 hz as above) into 150 ohms. In blue is what happens with the Bass EQ switch turned on. it’s a fairly gentle broad rise that, at its peak, is only 3 dB higher than the reference level. The peak is broadly centered around about 80 hz. Note this nicely compensates for the low frequency roll off as the response is still a bit above 0 dB even at 20 hz. As far as bass EQ goes, this is much more subtle than most. And the channel balance problem goes away with the EQ turned on.

CHANNEL SEPARATION: Here’s the channel separation and it does very well for something so tiny with the two channel jammed close together—a mostly constant 46 dB. Note this is driving a difficult 15 ohm load. The separation improves into higher impedance loads:

1 KHZ SQUARE WAVE PERFORMANCE: The E5 also does really well here. Unlike when testing DACs with square waves, there’s no ringing from the low pass filters all DACs have. So here it shows the flat frequency response (flat top of the waveform) and stability of the amplifier (lack of much ringing):

10 KHZ SQUARE WAVE PERFORMANCE (added 4/7): The dScope above makes a great 24 bit high resolution oscilloscope but only up to 96 Khz. This is fine for testing digital sources (players, DACs, etc.) but to really “stress” an analog amplifier you can use a 10 KHZ signal with a very fast rise time (from a 25 Mhz Tektronix AFG3022 Waveform Generator). The signal is measured with a 100 Mhz digital oscilloscope to evaluate the “speed” and other behavior of the amplifier. The red waveform on the bottom is the input to the amplifier and the blue trace on top is the output. The rounded corners represent the high frequency roll off and the slope of the rising edge represents the rise time and slew rate. This is decent, but not high-end, performance:

Here’s a ‘zoomed’ view of the rise time. Rise time is usually specified from the 10% to the 90% point. I didn’t use the on-screen cursors here but the time from –0.4 volts to + 0.4 volts is about 4.2 uS. The slew rate is the “flat” sloped part of the line and is about 0.4 v/uS. That sounds like a really bad number but, in practice, an amplifier only needs about 0.2 v/uS per volt of RMS output to reproduce a 20 Khz waveform perfectly. From a 44 Khz sampled digital source (i.e. CD quality audio) that’s the fastest slew rate you need. Even a 20 Khz perfect digital square wave comes out of a 44 Khz DAC as a 20 khz sine wave. So the 0.4 v/uS of the FiiO E5 means it can reproduce 20 Khz up to about 2 V RMS without slew limiting. And, because it clips around 1.4 V RMS, there’s a decent safety margin here.

TECH SUMMARY: The performance is impressive in most areas given the size and price. The extremely low 0.7 ohm output impedance and 100 mW into 16 ohm power level at low distortion are the stand outs on the good side. The bass EQ is subtle and overcomes the slight LF roll off nicely.