Fiio E12DIY Portable Amplifier

It’s kind of appropriate to be returning to review a new Fiio amplifier given that my very first portable amplifier was the Fiio E11. The E11 was a great starting amp for me, but the E12DIY is in a whole different league!

Overview

02230003The E12DIY is a special project from Fiio and is a limited editing offering for audio enthusiasts and tinkerers. The DIY is designed to let enthusiasts tweak the amp by changing op amps (more on that later), capacitors and resistors, but it begins life as a very capable portable amp even if you do nothing to modify it.

Because of the modifiable nature of the DIY, the specs provided (other than dimensions) are indicative and by no means fixed:

  • Dimensions:  124 x 65.5 x 14.5mm
  • Weight:  163g
  • Signal-to-Noise: 110dB
  • THD: 0.005%
  • Power: 600mW to 16 ohms

Inside the DIY’s box you’ll find a soft carry pouch, a hex key for opening the case, a tool for removing the op amps, a USB charging cable, 3.5mm to 3.5mm interconnect, rubber bands to attach the amp to your player, and a tin containing a variety of op amps, buffers, capacitors, resistors, and adapters.

Design & Features

The E12DIY is a relatively large amplifier, but it’s slim so total volume is similar to other portables like the Tralucent T1 – it’s just packed in a different shaped box. Personally, I figure that the moment you add an amp to a portable rig you’re choosing to sacrifice “pocketability” so they’re all going to be much the same overall once total size and weight are considered. Sure, there are tiny offerings out there like the Shozy Magic and Ray Samuels Mustang, but the majority of amps are similar in overall size and weight.

The E12DIY is a little heavier than other amps I’ve tried, partly due to its solid aluminium shell and partly due to its large battery. I imagine that the battery also partly defines the DIY’s form factor too, but the battery is a key part to the E12DIY’s performance so no complaints here.

The E12DIY is sold (if you can still find one) in either natural aluminium silver or in a gold finish that I haven’t seen “in the flesh”. Both colours differentiate the DIY from the standard E12 models which are black.

Connectivity & Controls

The E12DIY is nice and simple – 3.5mm input and output jacks (1 of each), a micro USB power socket, 2-position gain switch (high / low), and a volume knob that doubles as a power switch (zero volume = amplifier off). Unlike the standard E12 model, there is no bass boost switch or crossfeed circuit. According to comments I read somewhere from Fiio, the E12DIY was deliberately kept simple to allow more space for the best (simplest?) possible audio and power circuit designs and I believe it was a great choice.

Power

02230001Fiio struck a perfect balance with the design of the E12DIY by making it low-powered enough to drive sensitive OEMs, while also providing a high gain mode and plenty of power to drive much more challenging headphones.

The DIY pairs spectacularly with my Unique Melody Miracles, but is equally adept at powering my beyerdynamic T1s and Fischer Audio FA-011 LEs. That’s excellent versatility and means that the E12DIY could easily be the only portable amplifier you ever need to own. Of course, being a portable amp, it doesn’t quite replace a quality desktop, mains-powered amplifier, but is excellent for portable listening.

Something I really liked about Fiio’s provided set of buffers and op amps is that one of them (the LMH6321) is more focussed on high impedance loads (that’s Sennheisers and beyerdynamics mostly), while the other 2 are more general in operation. This means you can focus your amp to drive your exact headphone if you have a higher impedance model or you can keep it more versatile with the other buffer options. I should probably clarify though, that the other buffers still do a great job of driving high impedance ‘phones, it’s just that the LMH6321 is able to produce a little more oomph into higher impedance loads.

Sound Quality

Knowing that you can change the op amps and buffers in this amp, you’ve probably also surmised that the sound quality is variable as a result. Correct!

Because of the completely variable nature of the DIY’s staging and signature, I’m going to restrict this section to discussing the elements that remain consistent regardless of the chips used.

Noise Levels

In short? None!

01170025The E12DIY provides a completely black background with no noise or hash through any earphone or headphone I’ve tried with it. I did notice that using the BUF634 buffer introduced a potential for some noise to be picked up when I moved the interconnect and earphone plugs around inside the sockets (i.e. if I had the amp in my pocket and was walking), but I think this might have been a sign that I needed to re-seat the buffer by removing it and plugging it back in to ensure full contact in the socket. In any case, this was a situational issue while 95% of the time the amp was dead silent with this buffer and is 100% silent with my preferred LME49600 buffer, bur more on that later.

Back to discussing noise levels, the most noticeable benefit of a black background is that it allows every nuance, detail and texture of your music to be heard easily and clearly, but without having to over-emphasise anything. The E12DIY is able to deliver incredible clarity and detail while never sounding like it colours or enhances anything.

Channel Separation

Some years back I worked in car audio, designing and installing stereo systems. My focus was always sound quality and imaging, not necessarily sound pressure levels (i.e. ear-drum-rupturing volume). One of the tricks I often employed to create epic sound quality without spending too much money was to have separate amplifiers for each channel. For example, we’d use a 2 channel amp for the left side of the car (1 channel for the front and 1 channel for the rear) and a second 2 channel amp for the right side of the car. This kept each half of the stereo signal completely isolated so there was nearly zero crosstalk (only what occurred inside the car’s head unit). The term crosstalk refers to the sound from one channel bleeding slightly into the other channel and it has the ability to compress or completely kill the stereo image.

The reason I told that little story is because some amps do a better job than others at replicating this type of isolation of the 2 stereo channels. You can always tell when an amp does it well because the auditory image is always deep, beautifully defined, and engaging. The E12DIY does this extremely well! There are no crosstalk measurement published, but to my ears, the stereo channels are beautifully isolated and this is particularly true when using the OPA1611 op amps (2 mono op amps being used much like my 2 separate car amp analogy above).

Overall, the E12DIY’s ability to provide a “blank canvas” for the sound and to keep the stereo channels well isolated results in a wonderfully fun foundation with which to chop and change op amps and buffers to tailor the sound to your tastes and your gear while always maximising the performance of the components you install.

Op Amps and Buffers

I am a complete newbie when it comes to op amps and buffers, or at least I was when I bought the E12DIY. I would suggest that I have progressed from newb to beginner or amateur over the last few months, but am still far from an expert so what follows is a layman’s explanations of what I have discovered and learned with the chips supplied by Fiio and a few others I’ve bought myself.

Op Amps vs Buffers

02230012My layman’s understanding of op amps and buffers is that they are both very similar, but used differently. In my understanding, an op amp processes the incoming signal a bit like a pre-amp. The buffer then provides the gain (or voltage) to drive the signal into the headphones. To put it another way, the signal comes from your device (let’s say an iPod line out) and is first fed to the op amp which outputs an amplified signal. The amplified signal now needs power applied to allow it to effectively drive the headphones you’re using and this is the role of the buffer as I understand it.

As I said, I am still learning this area of audio and electronics, but I think of the op amp as a pre-amp of sorts and the buffer as the interface between the amplifier and headphones – the engine that drives the headphones according to the directions provided by the op amp.

If you know more about this topic and can clarify (or correct) my explanation, please feel free to share your knowledge with me and others via the comments section.

What Fiio Provides

The silver tin that comes with an E12DIY contains a selection of 4 op amps and 3 buffers. The op amps essentially offer different flavours of sound while the buffers offer a combination of flavouring, but also tailoring the power output to suit your chosen ‘phones.

The op amps provided are:

  • AD8620
  • OPA1611
  • OPA604
  • AD797

02230007I will hopefully be able to dedicate a whole post to the different sounds and flavours of various op amps in the near future, but my personal preference from these op amps is the OPA1611 which balances near-neutrality with a touch of bass warmth and lots of detail and clarity.

Until I can write in more detail about these op amps, there is some great discussion of different op amps scattered throughout the E12DIY thread over on Head-Fi.

The buffers provided are:

  • BUF634 (general)
  • LME49600 (general)
  • LMH6321 (more focussed towards powering high impedance headphones)

To my ears, the BUF634 and LME49600 provide different presentations of the sound with the BUF634 creating a more intimate, warmer presentation and the LME49600 feeling more spacious and transparent. The BUF634 might have a slight edge in the texture and weight of midrange, but I find myself preferring the LME49600 and the consensus (by a small majority) on Head-Fi points towards the LME49600 being the preferred buffer.

The LMH6321 presents sound quality that, overall, is almost on par with the LME49600, but it is able to provide greater power and therefore may perform even better than the LME49600 when paired with higher impedance headphones. THe LMH6321 is a bit of a specialist in that respect because it is less capable with lower impedance ‘phones than the other buffers. It still sounds great, but just not as great as the other two “generalist” buffers. If I were using the E12DIY solely with a headphone like the Sennheiser HD650 or beyer T1, the LMH6321 would likely get the nod.

Extra Adapters

In addition to the range of supplied chips, Fiio went one step further and provided all manner of adapters so you can try your own selection of op amps. The design of the E12DIY won’t allow for DIP-8 style op amps like the OPA2107, LM4562, or MUSES 01 (to name a few), but you can grind / file the inside of the case slightly to allow sufficient clearance if you’re brave enough. So far I’ve resisted this urge because I’m worried that it would require making the aluminium housing a bit too thin, but maybe I’ll get brave one day…

Back to the supplied adapters though. When you lift out the foam inside the tin full of op amps, there are a myriad of adapters stuck to the bottom of the foam (just using the 8 pin connectors pushed into holes in the foam). These adapters include options for both buffers and op amps including dual and mono varieties. It means you can have plenty of fun trying unusual, cheap, expensive, and exotic op amps to your heart’s content… so long as you’re happy to wield a soldering iron. No soldering is required with the stock provisions, but any op amps or buffers you buy yourself will either require soldering (for surface mount options) or filing / grinding (for DIP-8 options).

So far I have only tried an AD8599 which is the same op amp as used in the Tralucent T1 and while it’s magic in the T1, I preferred the OPA1611 in the DIY.

Summary & Wrap

01170026As I write this summary, there are probably a few new, retail units of the E12DIY in captivity so if you’ve read this far and it’s still close to April / May 2014 then you might want to get hunting for a remaining E12DIY at a dealer. For the price you pay you will not find a comparable package of sound quality, power and bespoke sound. It’s a sleek package of brushed aluminium that happens to perform somewhere in the range of twice it’s price point. In terms of transparency, neutrality and overall quality, the E12DIY will absolutely not disappoint the most demanding users as a portable amplifier and will be equally as much a bargain second hand (if you can find one) as new.

With the E12DIY, Fiio seem to have announced their arrival into making serious, headphone performance gear and have taken a step beyond their previous (excellent) mid-fi offerings. The recently released X5 portable media player is a further step in this direction and I’m looking forward to reviewing it in the coming weeks so stay tuned!

Audio-gd NFB-5.2 DAC/Amp

For a while now I’ve been using a Creative X-Fi USB soundcard as my quality DAC and amplifier and it’s done an amazing job, but as a USB-powered amp, it was never going to shine with any truly high quality headphones. And so it came to pass that I decided on my first step into the realm of dedicated headphone amplifiers – the Audio-gd NFB-5.2

I decided on the NFB-5.2 because it is a combination digital-to-analogue converter (DAC) and headphone amplifier. Reviews I read seemed good and it was available from the great crew at Addicted to Audio where I buy a bunch of my stuff (often with their wise advice).

Specifications

Signal to noise ratio:  119dB
Output power:  3500mW @ 25 ohm – 150mW @ 600 ohm
Output impedance:  2 ohm (headphone out)
Sampling support: 44.1kHz – 192kHz (16-bit or 24-bit)
Inputs:  Optical, Coaxial, USB

I’ll review the NFB-5.2 in 3 stages: first a quick overview, then the DAC, and then the amp.

Overview

The front panel of the Audio-gd NFB-5.2The NFB-5.2 is quite simple and that’s good. On the front of the unit is:

  • A power button (left)
  • Volume control (right)
  • 6mm stereo headphone socket with a securing system to keep the plug in place
  • Simple, 4 character, blue display
  • 4 control switches (under the display)

All of the buttons and the volume knob are brushed metal and the case of the unit is also all metal. It’s not super heavy, but seems very well built.

The 4 buttons under the display allow you to select different options.

Button 1: Filter

The “Filter” button lets you select from a number of filters used to remove unnecessary frequencies from the DAC output. It’s generally not something that you’ll notice in the sound and is used more to remove subtle digital artefacts and noise from the signal. I played around a bit and now leave my NFB-5.2 set to filter #6 which has creates an output that looks like this:

A graph showing the effect of filter #6

Filter #6 frequency response chart

As you can see, it only starts to affect the sound at around 20kHz and above – all frequencies which are beyond normal human hearing limits, but it should help to clean up the overall signal.

There’s a full listing of the possible filter options here.

Button 2: DAC/HP

This button has 4 options. Options 1 & 2 activate the headphone amplifier output either without (option 1) or with (option 2) the OP amp. Options 3 & 4 activate the RCA line outs on the back of the NFB-5.2 and allow you to use it as just a DAC with a separate dedicated amplifier. Once again the two options are for the OP amp being used or not used.

The OP Amp

The OP amp (OPA) is modular circuit that can colour the sound to suit individual tastes. Audio-gd supply the NFB-5.2 with their OPA-2134 model, but you can buy 3 different options as aftermarket (or custom) options. The 3 other OPAs offer neutral sound, warm sound, or dynamic sound. I hope to review the OPAs separately in the future.

In relation to the OPA-2134 that comes standard, my feeling is that it’s better left switched off. Engaging the OPA using setting 2 or 4 of the DAC/HP switch results in a flatter sound with less depth and a weaker sound stage. There’s really no improvement that I can discern.

Button 3: Gain

A very simple option here: “high” or “low”. The “high” option apparently adds a 12dB boost across the range (from the DAC, not the amp). When I’ve used high gain, the sound seems to become a bit edgy when compared to the equivalent volume on low gain. I’m sticking to the low gain option, but others might like the extra energy delivered by the high gain.

Button 4: Input

3 options here: USB, Optical or Coaxial. Very simple.

All work the same although I have read claims of slight sound variations between the 3 inputs. As I don’t have a source with all three outputs I can’t do a fair comparison.

NFB-5.2 DAC Stage

The DAC in the NFB-5.2 is really nice. I’ve run my Bang & Olufsen BeoLab 3 speakers using the line out of the NFB-5.2 and the sound is beautifully clean, well-layered with plenty of separation between instruments and creates a stunning sound stage through the BeoLab 3’s acoustic lenses.

As I’ve already explained, the filter system is a nice feature for those who are more technically inclined, but once it’s set you’ll probably not think about it ever again so essentially the NFB-5.2 DAC stage is a set-and-forget affair and it does a fine job.

The TE8802 Chip

The NFB-5.2 is an upgraded version of the NFB-5. The only difference (according to what I’ve read) is the inclusion of the TE8802 USB chip. The TE8802 allows for asynchronous transfer… yeah, I didn’t understand either!

What all this really means is that the NFB-5.2 should be less susceptible to minor issues with errors created by the USB chip in your computer slowing down or running inconsistently. In short, it’s a minor upgrade that’s nice to have, but likely won’t be a game changer.

Compatibility

The NFB-5.2 worked perfectly with my laptop running Windows 7 (64-bit) and MediaMonkey as my media player. The Audio-gd drivers, combined with the TE8802 chip allow the NFB-5.2 to work all the way up to 192kHz/24-bit. After doing some reading, I believe there’s no real benefit (and possibly some disadvantages) to using 192kHz output sampling so after testing that it worked, I reverted to 96kHz sound and it’s brilliant!

It’s worth noting that ASIO drivers seem to give the best sound and best compatibility with the NFB-5.2. I started out using WASAPI drivers, but they created some nasty cracks and pops from the computer (not the NFB-5.2’s error) and the sound seemed better when using ASIO.

NFB-5.2 Amp Stage

The amplifier in the NFB-5.2 is probably slightly weaker than the DAC. Where the DAC seems to be beautifully clean and crisp, the amp strikes me as just a touch soft around the edges. Perhaps it’s just a warm sound signature when I prefer a more analytical sound in general. There is also a hum that’s audible through my Shure SE535 LE in-ear monitors, but read on because that’s not necessarily a bad sign.

Power

The NFB-5.2 has plenty of grunt. I’ve just received my new Sennheiser HD650s (thanks Gavin!!) and the NFB-5.2 volume control only just clears 50% (on low gain) to drive the 300ohm HD650s. There are very few (if any) conventional headphones that the NFB-5.2 couldn’t drive. Obviously there will be much more expensive amps that will sound better, but it’s got the power.

Noise

This is a tricky one. With the 300ohm HD650s, the NFB-5.2 sounds pitch black – no noticeable noise. On more sensitive cans like the Audio Technica AD900s, there is some hiss when you turn the volume right up (>75%), but none at normal listening volumes. From this perspective, the NFB-5.2 is nice and clean.

What put me off slightly here is the noise I heard when I connected my Shure SE535 LEs. The Shures are hyper sensitive (119dB SPL/mW) and this showed up a background hum from the amplifier. The NFB-5.2 is listed with a 119dB signal to noise ratio so there’s a good chance the SE535 is picking up the end of the NFB-5.2’s quality control limits and that’s OK – it’s not meant for driving hyper-sensitive IEMs. The main reason for my concern was that the hum isn’t balanced – it is louder in the left channel. That might not mean anything, but I look forward to testing the SE535s on another NFB-5.2 next time I visit Addicted to Audio. Maybe the right channel on my unit is just slightly cleaner than Audio-gd’s quality control standards, but I’m keen to make sure there’s not an error somewhere in the circuitry of my amp.

NOTE: It’s important to note again here that an amp like the NFB-5.2 is not really designed to drive super sensitive, low impedance monitors like the SE535s so this isn’t a major flaw, but until I can test a few other similar amps, the unbalanced hum leaves a tiny doubt in my mind.

Control

The NFB-5.2 amp is really well controlled. My Ultrasone HFI-680s can be quite bassy and that can cause them to lose clarity and control if not well driven. The NFB-5.2 does a great job of tightening the bass and keeping it punchy and full.

I mentioned earlier that the NFB-5.2 amp seems slightly soft around the edges and while that is definitely the case, there is no doubt that it does an amazing job for the cost. It’s an incredibly good amp for the cost (especially when you get a great DAC built-in).

Overall Conclusion

Would I buy the NFB-5.2 again if I had my time over?

Absolutely!!

For less than US$400 plus shipping costs (about AU$480 here in Australia) you get a really nice DAC with a solid, powerful amp that will drive anything very well. The amp may tend towards being slightly warm, but it reveals detail well and definitely won’t create fatiguing edginess in the sound. Being able to bypass the amp in the future while maintaining the really nice DAC stage of the NFB-5.2 is a massive bonus!

The high gain mode seems to bring some unwanted distortion or edginess to the sound, but there’s so much power on tap that you don’t need to use it if you don’t want to.

Of course, there’s also the fact that you can buy different OP amps for around $40 each and modify the sound to your tastes. I look forward to trying these out and sharing some thoughts in a future blog post.

If you’re looking for a nice entry point into DACs and amps, the NFB-5.2 is an excellent option – well priced, clean, powerful and simple to use – I’d recommend it.