FiiO AM3 - Balanced Amplifier Module for X7


Formerly known as K400Lover
Pros: Sound: Way more resolution and clarity
Cons: Sound: None
Have to get your headphones balanced too
When I switched from my X5 to X7 I stumbled upon the option "AM3 balanced" in Brookos review. I started browsing around what this is all about and got the feeling, this is something that actually may make sense.
My first try was then with my TripleFi 10 and the FiiO cable (RC-UE2B).
The results were really impressive! But I didn't know if maybe just the cable was so much better or if it really also was the balancing. So I tried my other headphones too.
Next was Shure SE535 with a Fidue A83 replacement cable that is balanced and fits to SE535. Same impressive result.
Now I had to try the more difficult ones. Over ear AKG K400 and K500.
For the K400 I bought a cheap video camera cable that had a 2.5mm balanced plug and soldered it myself to the K400 drivers. The result looks crappy, but hey it sounds fantastic !!!
Next round was using a K701 cable, solder the four inside wires in a balanced way to the K500 and also manually solder a 2.5mm plug after cutting of the original K701 plug. This result looks like original AKG and ... yes also this one sounds better!
To sum it up I guess I can assure that we should all go balanced. It seems to be clearly better that unbalanced. I compared to AM3 unbalanced and AM2A.
Which just leaves me with one question: Why is the industry not only offering balanced mode? It seems not to be more expensive and creates better sound. Any opinions about it?

P.S. IN all the praising for balanced I almost forgot: This is about an AM3 review. Since I have all modules I would rate them like this:
AM3 balanced > AM2A > AM2/AM5 > AM3 unbalanced > AM1
But all on a high level. I could also live with any of them alone.


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Pros: Sound quality, power output, low impedance, easy to swap in and out, balanced option as well as single ended, better battery life than AM5
Cons: Still relatively low battery life compared to alternatives
For larger (1200 x 800) images, click any picture


A lot of you will see the style and information with this review as being pretty similar to the one I did on the AM2 and AM5. And the reality is that a lot of the physical aspects are very much the same. So for similarity I can't do much about it. I can assure you however that I performed the same testing, and the same comparisons I've done previously. I reviewed FiiO's TOTL Android based touch screen DAP – the X7 – in early November 2015, the AM2 module in February 2016, and the AM5 module in May 2016.
Please note that the X7 (with subsequent firmware updates) is now a much more complete DAP than when first released. I can now go artist, album, track, the DAC works beautifully, the blue light can be turned off, the battery indicator seems to be a lot more accurate, and with the release of most of the amplifier modules, there is plenty of choice for no matter what headphones you are driving.
By now, most Head-Fi members should know about the FiiO Electronics Company. If you don’t, here’s a very short summary. FiiO was first founded in 2007. Their first offerings were some extremely low cost portable amplifiers – which were sometimes critiqued by some seasoned Head-Fiers as being low budget “toys”. But FiiO has spent a lot of time with the community here, and continued to listen to their potential buyers, adopt our ideas, and grow their product range. They debuted their first DAP (the X3) in 2013, and despite some early hiccups with developing the UI, have worked with their customer base to continually develop the firmware for a better user experience. The X3 was followed by the X5, X1, X3 2nd Gen (X3ii), X5 2nd Gen (X5ii), M3 and X7. They also have a full range of amplifiers, DAC/amps, cables and are even starting to develop earphones.
FiiO’s products have followed a very simple formula since 2007 – affordable, stylish, well built, functional, measuring well, and most importantly sounding good.
The X7 and add on AM3 module were provided to me gratis as a review samples. I have made it clear to FiiO in the past that I did regard any product they sent me as their sole property and available for return any time at their request. I have continued to use X7 and its modules for follow up reviews, and I recently inquired if I could purchase the devices from FiiO. They have insisted I keep the X7 + modules for my own use. So I acknowledge now that the X7 I have is supplied and gifted completely free of any charge or obligation. I thank FiiO for their generosity.
I'm a 49 year old music lover. I don't say audiophile – I just love my music. Over the last couple of years, I have slowly changed from cheaper listening set-ups to my current set-up. I vary my listening from portables (including the FiiO X5ii, X3ii, X7, LP5 Pro and L3, and iPhone 5S) to my desk-top's set-up (PC > USB > iFi iDSD). I also use a portable set-up at work – usually either X3ii/X7/L3 > HP, or PC > E17K > HP. My main full sized headphones at the time of writing are the Beyerdynamic T1, Sennheiser HD600 & HD630VB, and AKG K553. Most of my portable listening is done with IEMs, and lately it has mainly been with the Jays q-Jays, Alclair Curve2 and Adel U6. A full list of the gear I have owned (past and present is listed in my Head-Fi profile).
I have very eclectic music tastes listening to a variety from classical/opera and jazz, to grunge and general rock. I listen to a lot of blues, jazz, folk music, classic rock, indie and alternative rock. I am particularly fond of female vocals. I generally tend toward cans that are relatively neutral/balanced, but I do have a fondness for clarity, and suspect I might have slight ‘treble-head’ preferences. I am not treble sensitive (at all), and in the past have really enjoyed headphones like the K701, SR325i, and of course the T1 and DT880. I have a specific sensitivity to the 2-3 kHz frequency area (most humans do) but my sensitivity is particularly strong, and I tend to like a relatively flat mid-range with slight elevation in the upper-mids around this area.
I have extensively tested myself (ABX) and I find aac256 or higher to be completely transparent. I do use exclusively red-book 16/44.1 if space is not an issue. All of my music is legally purchased (mostly CD – the rest FLAC purchased on-line). I tend to be sceptical about audiophile ‘claims’, don’t generally believe in burn-in, have never heard a difference with different cables, and would rather test myself blind on perceived differences. I am not a ‘golden eared listener’. I suffer from mild tinnitus, and at 49, my hearing is less than perfect (it only extends to around 14 kHz nowadays).
This review is essentially about the AM3 balanced amp module released by FiiO for the X7. For a detailed look at the features of the X7, and a quick run-down on the AM1 (default) IEM module, I would recommend you read my X7 review or indeed any of the 30 something reviews on the X7 currently listed.
This is a purely subjective review of the AM3 balanced amplifier module – my gear, my ears, and my experience. Please take it all with a grain of salt - especially if it does not match your own views.


Front of the retail box
Rear of the retail box
The AM3 arrived in a small black retail box measuring approximately 90 x 120 x 25mm. On the front of the sleeve is a picture of the bottom half of the X7 with AM3 module attached and some text telling you that this is the AM3 amplifier module. On the rear of the box are QR codes which will take you to FiiO’s website or Facebook page.
Removing the outer packaging reveals a plain tin box with a nice powder coated finish. Removing the lid reveals a black cardboard envelope, and under this is a foam cut-out with the AM3 module nestled safely inside.
The powder coated tin
Accessory envelope
Inside the envelope is a warranty booklet in multiple languages, a full set of stickers (which match the ones from the X7) and 2 replacement screws. The stickers are a nice touch and show FiiO are thinking about their customers. If you’ve brought and applied stickers to your X7 already, the last thing you’d want is a new amp module with no adornments. Although I don’t use them, I can appreciate the foresight.
Stickers and documentation
AM3 safely nestled in its foam enclosure
As far as the AM3 goes, the other nice thing to note once again is the rubber dust cover/protector over the connection pins. So far everything is a mirror of the AM2 and AM5 modules, and this includes the lack of specifications on the packaging. The good thing is that FiiO have already listed the specs for the AM3 in the X7 section on their website. One last thing before we conclude this section – the case is actually large enough to store 3 modules. So my suggestion for FiiO would be to modify at least one of their releases to give that option. If not, then you can modify yourselves (see below).
Nice touch - internal rubber sheath
My modified container for all modules
The table below lists most of the relevant specifications. I have (as a comparison) also listed specifications from the default AM1 and also the AM2 and AM5 modules.
AM1 Module
AM2 Module
AM3 Module (SE)
AM3 Module (Bal)
AM5 Module
~ 64 x 25 x 16mm
~ 64 x 25 x 16mm
~ 64 x 25 x 16mm
~ 64 x 25 x 16mm
~ 64 x 25 x 16mm
Voltage amplification
Current Drive
TPA6120 A2
S/N (H/O)
≥115 dB (A-Weight)
≥118 dB (A-Weight)
≥115 dB (A-Weight)
≥115 dB (A-Weight)
≥120 dB (A-Weight)
<0.0008% (32Ω/1 kHz)
<0.001% (32Ω/1 kHz)
<0.001% (32Ω/1 kHz)
<0.0008% (32Ω/1 kHz)
<0.001% (32Ω/1 kHz)
Output into 16 ohms
>200 mW (16Ω/1 kHz)
>350 mW (16Ω/1 kHz)
>250 mW (16Ω/1 kHz)
>420 mW (16Ω/1 kHz)
>800 mW (16Ω/1 kHz)
Output into 32 ohms
>100 mW (32Ω/1 kHz)
>300 mW (32Ω/1 kHz)
>190 mW (32Ω/1 kHz)
>540 mW (32Ω/1 kHz)
>500 mW (32Ω/1 kHz)
Output into 300 ohms
>10 mW (300Ω/1 kHz)
>30 mW (300Ω/1 kHz)
>25 mW (300Ω/1 kHz)
>70 mW (300Ω/1 kHz)
>55 mW (300Ω/1 kHz)
H/O impedance
<0.2 Ω (32Ω)
<0.5 Ω (32Ω)
<0.3 Ω (32Ω)
<0.3 Ω (32Ω)
<0.5 Ω (32Ω)
Peak output voltage
>5.2 Vp-p
>8.8 Vp-p
>7 Vp-p
>11 Vp-p
>11 Vp-p
Peak output current
>250 mA
>250 mA
>80 mA
>160 mA
>250 mA
Channel Separation
>73 dB (32Ω/1 kHz)
>72 dB (32Ω/1 kHz)
>72 dB (32Ω/1 kHz)
>110 dB (32Ω/1 kHz)
>72 dB (32Ω/1 kHz)
Play time
9 hours+
8 hours+
6 hours+
6 hours+
6 hours+
The AM3 has the same dimensions as the AM1, AM2, and AM5. The main differences are internal, and of course also the addition of the balanced 2.5mm port. The AM3 follows the same look of the AM2 and AM5 with a darker shade of the powdered titanium appearance. Otherwise they all look and feel identical. The AM2, AM3 and AM5 colouring appears to be the same. There is white text on the back of each designating the model number.
Left = 3.5mm SE, middle = USB, right = 2.5 mm TRRS balanced
Internal view ​
I think one of the best things FiiO has done with the AM3 module is to include both single ended and balanced ports in the one module. On the left is a 3.5mm single ended port, and on the right a standard 2.5mm balanced port (TRRS).
Side view
Underside of the module
Replacing the modules is extremely easy – just a matter of using the small hex screwdriver included with the X7 – undoing two screws, sliding one module out, and sliding the new module in. The fit on the AM3 is perfectly flush, and the only thing very apparent with the AM3 fitted is the change in colour (compared to X7). This of course disappears when used with a cover for the X7 (if owned).
Attaching/detaching the modules
With cover fitted, there are no visible colour differences
Although you can’t see them, it is probably a good idea to mention the internal electronics (also see the table above). The AM3 uses a brand new amplifier chip from Texas Instruments – the OPA1622 – which has been designed exclusively for audio products. It is the successor to the OPA1612, and boasts some pretty impressively low distortion figures. The AM3 utilises a pair of OPA1622 for the single ended output, and 4 of them in the balanced output. FiiO's website quotes “an ultra low THD+N of -119.2 dB (0.000018%) while driving a 32 ohm load at 10-mW output power – 12 times better than the most similar competitive product”. In both balanced and single ended modes, one OPA1622 is used for voltage amplification, and the second as a current buffer.
Image courtesy of FiiO
Everything is combined on a single circuit board (unlike the AM5's dual boards), and there is a protection cover sandwiched between the board and housing to protect the amplifier chips and other components.
Whilst the AM5 has most powerful output of the X7's amplifier modules into 16 ohms (AM5 = 800 mW vs AM3 = 420 mW), the AM3 actually outperforms it in balanced mode at higher impedances delivering an impressive 540mw into 32 ohms (vs AM5 500 mW) and 70 mW into 300 ohms (vs AM5 55 mW). Sadly, I have no balanced cable for my HD600 – but you can bet that will shortly be on my list of things to buy.
So the specs are listed above, bit what does that mean in the real world? This time (because I didn't have a balanced cable), I couldn't test my HD600, but I did have a pair of single-ended and balanced MMCX terminated ALO Audio Tinsel cables, and the perfect IEM in the form of the MEE Pinnacle P1 (50 ohms impedance, 96 dB sensitivity). I also had the newly arrived Fidue Sirius and the bonus of having it balanced plus having an adaptor to quickly convert to single ended.
The first test was to measure the P1 in balanced mode, switch to the single-ended cable and remeasure. I then went back to the balanced cable, and checked again using Fidue's adaptor. Everything matched perfectly – so from that point on I simply left everything in balanced, and simply used the adaptor when comparing with single ended. Because I had everything here – I then used all 4 modules and measured the C-rated decibel output of a 1 kHz test tone with the P1 as load. Unfortunately – because the load was pretty easy to drive, you won't see the same differences in volume, and for now I don't have the right adaptors to drive a more powerful mode to showcase the differences. When I manage to get the correct cable for my HD600 – I'll come back and redo this.
But for now:
In each case the X7 was in low gain mode, no EQ, using a 1 kHz test tone, constant 40/120 volume setting.
AM1 (SE) = 69.9 dB
AM2 (SE) = 75.3 dB
AM5 (SE) = 75.6 dB
AM3 (SE) = 73.3 dB
AM3 (bal) = 77.6 dB
What it does show is that even at a relatively benign 50 ohm load, as far as power output goes, the AM3 in balanced mode will outperform all the other amps into higher impedances.
Although FiiO publishes their own real world tests with their modules, I also like to conduct my own. I noticed FiiO used relatively easy to drive IEMs and earbuds – their own M3 for the single ended test and the SE846 for the balanced test. Both achieved “+6 hours” at 58/120 and 50/120 respectively.
For my test I turned again to the MEE P1 which with its lower sensitivity and higher impedance really needs a little more power than most IEMs. I stayed with the 40/120 power on the X7 – because with the P1 in balanced mode the average track was hitting the 65-70 dB mark which is pretty normal listening for me. I then shuffled my entire library, and started playing – turned the screen off (after disengaging both wifi and bluetooth). I was using FiiO's pure music mode.
In balanced, the X7 managed to last 7 hours and 5 minutes – which I thought was a pretty good effort. I'd imagine that once I get the HD600 balanced cable – I should be able to run them comfortably at around 60/120 volume, so even with the increased volume I should have no problems running 6+ hours.
I repeated the test in single ended at the same volume, and the running time was almost identical – this time clocking up 7 hours and 9 minutes.
Of course your results are going to vary depending on the volume you use, the load you're driving, the amount of screen time you have on, and the apps you have running.
SONICS (subjective)
So here we are again, after covering the specs, build, power and effect on battery life. I'll repeat what I said last time - my ears are probably not as sensitive as many of you, I volume match very closely, and I’m subject to the same amounts of potential placebo as all humans. The swapping for the comparisons were as quick as I could make them to preserve auditory memory (same procedure as before – screws undone – swap units, adjust volumes to the pre-set levels, and listen). I varied between rapid swapping (portions of a track about 10-15 seconds) and longer listening periods (a full track at a time).
I used a mix of my usual test tracks - and concentrated mainly on tracks exposing detail, dynamic contrast, sound-stage, bass quantity and vocal quality. I'm just going to summarise here – rather than go through section by section – because a lot of the time the results were so close that in the end I was guessing.
Remember this is pretty subjective!
AM3 SE vs balanced
I'll call this one early. To me they sound the same. I spent hours trying to track down any differences, and either my ears aren't sensitive enough, or there simply aren't any. Stage, imaging, and immersion had no difference – and that's probably where I expected to hear something (crosstalk). As far as tonality goes – I can't discern any difference at. A couple of times I've thought I had it nailed, only to discover I'd bumped the volume button, and when repeating the differences disappeared. The big difference for me is in power output (volume).
AM3 vs AM5
Again – with the P1, these two amp are so close they are almost identical. Staging, imaging and immersion have no real discernible difference, and there is no change in detailing. What I am getting is that the AM3 sounds ever so slightly more vivid (more present), with the AM5 being very slightly flatter. I really wish I could try this with the HD600 – as I think I would get a better sense of where the truth is. With the P1 – I'm favouring the AM3. I hate the term musical because it does a poor job of explaining anything – but that's what I'm reverting to because this module seems to be drawing a little more out of the music I listen to. One thing I will say – the changes are small, and again both modules sound very good indeed.
AM3 vs AM2
Similar to the comparison with the AM5 – except more noticeable. The AM2 is a little warmer, a little flatter, and a little relaxed in its presentation. The AM3 in comparison is cleaner, clearer, more vibrant, and to me more dynamic.
AM3 vs AM1
This is an interesting one because in terms of overall tonality the AM3 to me is a lot closer to the AM1. It has that same clean, and clear presentation. The difference is in the overall dynamics with the AM3 – it has more life, is more vivid, and there is a greater feel of dynamic contrast. Staging is once again very similar – but this time on pure imaging I'd give it to the AM3 by a small margin.
This was a lot harder to measure – as I couldn't use loopback (I didn't have a balanced to single ended converter). What I could do though was connect the MEE P1 to Veritas, use the X7 as DAC, and measure the P1 with ARTA using each amplifier module.
What you'll notice here is the same curve with no real deviations. Please ignore the section after 5 kHz as this is a combination of the P1's frequency response, the X7's DAC (under Windows) and Veritas not measuring well below 4-5 kHz (it always measures low).
What the measurements did show though was that the P1 is pretty linear under different amplification, and also that my readings earlier with the SPL meter are being accurately represented with Veritas and ARTA. I have no doubts that I'm not really showing what both the AM3 (balanced) and AM5 are capable of with a tougher load to drive – but until I get a balanced cable for my
In the graph – the two blue lines are the AM3 (darker is SE, lighter is balanced). Red and yellow is the AM5 and AM2 respectively, and the AM1 sits at the bottom (orange). Again the only reason the AM5 and AM3 balanced aren't showing more volume difference than the others is because they need a tougher load to showcase their strengths.
Sirius balanced
Sirius single ended with adaptor
I mentioned earlier that the Sirius comes balanced by default, and also with the adaptor I've been using for my quick switching for the comparisons. I'd be remiss if I left without mentioning the combo. The Sirius is quite vocal or mid-range centric as far as IEMs go, but it also has a brilliantly clean and clear and nicely balanced presentation. Couple that with clean, dynamic X7 plus AM3, and you have a combination that lovers of detail and clarity (without excessive brightness) are going to love. One of my favourite combos, and even rivals my U6 at the moment.


I'll keep this short, as I’ve pretty much already summarised everything – but once again to put it in a couple of sentences …..
The AM2 module (like the AM1, AM2 and AM5 modules) has a great build, is easy to fit, and measures as well as it sounds (check FiiO's specs). It will cost you some battery life from the original AM1, but in balanced mode it should have no issues driving headphones like my HD600.
Tonally the AM3 is closer to the AM1 than the slightly warmer AM2 and AM5 modules, but to me has a step-up in dynamic presentation, and is cleaner and clearer while avoiding being clinical.
I've managed to acquire 2 different balanced cables with MMCX connectors, and one with a dual pin configuration (for my U6), and I'm finding I just leave the AM3 in place all the time now. When I'm not using the X7 + AM3 (balanced), I'm switching to the L&P L3 (again balanced).
At an approximate release price of USD 99.00, if you own the X7 and have balanced headphones already, it is a no-brainer.
Once again thanks to Sunny at FiiO for giving me a chance to try the AM3.
Clockwise from left - AM1, AM2, AM5, AM3
Internals all look the same
Left to right - AM5, AM3, AM2, AM1
Two balanced DAPs - X7 + AM3 vs L&P L3
I don't hear the AM1 as having overpowering treble though - which probably means you are very treble sensitive.  So if you don't need a balanced output, I'd suggest you stick with AM2 or AM5.  The Muses chipset is a little warmer and will suit your preferences.
I am new to balanced amp modules. How would I set it up with my HD650. If you can advise, I would appreciate it


500+ Head-Fier
Pros: Balanced gives noticeable advantages over SE, drives a wide range of headphones well, overall build quality
Cons: Lower battery life, color doesn’t exactly match rest of X7
Table of Contents
  • Introduction
  • Specs
  • Build Quality
  • Battery Life
  • Sound quality
    • Volume-matched Comparisons with other amp modules
  • Conclusion
(Before I even begin with the introduction, I wanted to say that the above table of contents is for your convenience. I’ll also include a tl;dr summary at the beginning of each major section.)
Tl;dr: FiiO lent me the unit for my honest opinion, and a bit of background about myself.
[size=11.0pt]A little bit about me: I consider myself to be a relatively inexperienced audiophile, having only taken this hobby seriously for the past 2 or 3 years. Funnily enough, I actually began to take an interest in my headphone system with the purchase of a FiiO E7. The next logical upgrade from there was the FiiO E17, which I appreciated but soon found it a bit lacking in sound quality after I was exposed to other audio equipment. Now, after having been away from FiiO for a while I am now back with their X7 DAP.[/size]
[size=11.0pt]I tend to like a neutral sound signature, perhaps with a bit of warmth. But if one were to ask me to pick between a very warm or a very bright sound signature, I’d go towards the brighter one. I like a large variety of music including rock, pop, jazz, classical and orchestral, J-Pop and J-Rock, and C-Pop.[/size]
This review is specifically about the AM3 amp module designed for the FiiO X7 DAP. For a review of that particular player, you may want to click here for my review or take a look at the many other reviews of the X7.
I would like to thank FiiO for letting me demo all of the X7 amp modules in exchange for my honest opinion!
Before we go onto the rest of the review, a specifications table might be useful.
Amp Module
AM3 Balanced
Voltage Amplification
Current Buffer
Output into 16 ohms
>200 mW​
(16Ω/1 kHz)​
>350 mW​
(16Ω/1 kHz)​
>800 mW​
(16Ω/1 kHz)​
>420mW (16Ω/1kHz)​
>250mW (16Ω/1kHz)​
Output into 32 ohms
>100 mW​
(32Ω/1 kHz)​
>300 mW​
(32Ω/1 kHz)​
>500 mW​
(32Ω/1 kHz)​
>540mW (32Ω/1kHz)​
>190mW (32Ω/1kHz)​
Output into 300 ohms
>10 mW​
(300Ω/1 kHz)​
>30 mW​
(300Ω/1 kHz)​
(300Ω/1 kHz)​
>70mW (300Ω/1kHz)​
>25mW (300Ω/1kHz)​
Output Impedance
<0.5 Ω (32Ω load)​
<0.5Ω (32Ω load)​
<0.5Ω (32Ω load)​
<0.3 Ω (32Ω load)​
<0.3 Ω (32Ω load)​
S/N Ratio
≥115 dB (A-weighted)​
≥118 dB (A-weighted)​
≥120 dB (A-weighted)​
≥115dB (A-weighted)​
≥115dB (A-weighted)​
(32Ω/1 kHz)​
(32Ω/1 kHz)​
(32Ω/1 kHz)​
(32Ω/1 kHz)​
(32Ω/1 kHz)​
Channel Separation
>73 dB​
(32Ω/1 kHz)​
>72 dB​
(32Ω/1 kHz)​
>72 dB​
(32Ω/1 kHz)​
>110 dB​
(32Ω/1 kHz)​
(32Ω/1 kHz)​
Peak Output Voltage
>5.2 Vp-p​
>8.8 Vp-p​
>11 Vp-p​
>11 Vp-p​
>7 Vp-p​
Max Current Output
>250 mA​
>250 mA​
>250 mA​
>160 mA​
>80 mA​
Battery Life
9+ hours​
8+ hours​
6+ hours​
>6 hours​
>6 hours​
Build Quality
Tl;dr: Great build quality. That the color doesn’t exactly match the rest of the X7 is probably the only con.
The AM3 amp module, even this prototype that I am evaluating, exhibits some great build quality like the rest of the X7. Despite not being a production unit, the metal feels smooth and polished, with no rough edges. AM3 also snaps in easily, where it is flush, tight and secure to the rest of the X7’s body once you put in some screws.
It pretty much looks like it belongs with the rest of the player, if it weren’t for the fact that it’s a much darker shade of grey compared to the rest of the X7’s brighter silver color, like with AM2 and AM5. Honestly, this isn’t such a big deal for me since I’m not looking at the player for much of the time. There’s also the fact that you won’t notice this at all if you buy a cover for the X7.
Not much for me to complain about here, even at this prototype stage.
Battery Life
Tl;dr: You take a pretty substantial hit to battery life compared to AM1, but that’s the price of a powerful balanced amp and it’s no worse than the AM5.
Unfortunately, more power on tap means that the battery life will inevitably suffer. In AM3’s case, the hit to battery life is notable.
For single-ended mode, I conducted my battery life testing under the following conditions: the X7 powering the Etymotic ER4S at low gain at a volume level of 39, using the FiiO Music app in Android mode, and with the screen, pulsar light, Wi-Fi, and Bluetooth off. The music the X7 cycled through was mixture of CD-quality and high-res FLAC, as well as some DSD tracks. CD-quality FLAC tracks made up the vast majority of the music.
Under those constraints, as seen in the screenshot below I managed to get about 7 hours and 14 minutes of playtime. In comparison, with the AM1 amp module volume-matched and under the same conditions, I got 8 hours and 22 minutes of playtime. With the AM2 amp module under the same conditions and volume-matched, the X7 could play for 7 hours and 41 minutes. With AM5 powering the same headphones volume-matched and playing under the same conditions, the X7 could squeeze out 6 hours and 30 minutes out of its battery.
But wait, what about battery life under balanced mode, you might ask? Well, for that, since I don’t have any IEMs with balanced cables, I tested how long the battery could last using my Hifiman HE-400i headphones, which I do have terminated in balanced. Otherwise, the conditions remained the same as explained above. I also did a battery life test with the same headphone in SE, volume-matched and also under the same conditions, to examine the effect of balanced on battery life.
As seen below on the left screenshot, under SE on the 400i I got around 6 hours and 27 minutes of play time. With balanced mode on the same headphone as seen on the right screenshot below, I got around 6 hours and 56 minutes of play time. While such a difference may be surprising, I attribute this to the fact that I used shuffle mode when conducting battery life tests. Perhaps with SE, the X7 just happened to queue up more high-res PCM and DSD tracks, leading to the lower battery life seen here. I would expect that there really is no difference in battery life between SE and balanced out, like FiiO themselves have claimed.
AM3SE400i.png AM3Bal400i.png
Ultimately, you’re going to take a hit to play time compared to AM1 if you use the AM3 even in SE mode. However, given AM3’s better sound quality over AM1 and AM3’s balanced mode (as we will see in the next section), AM3’s battery life doesn’t seem that bad in comparison to the other amp modules. But it doesn’t change the fact that you won’t be playing music for very long under battery power with the AM3.
Last thing I want to stress – the AM3 unit I am using is a prototype. Thus, you can’t exactly take these battery life numbers as final, though they do match up with what FiiO claims.
Sound Quality
Tl;dr: AM3 balanced clearly sounds better than SE mode. While AM3 SE does well with IEMs, it struggles with full-sized headphones. But AM3 balanced probably does the best with full-sized headphones out of any X7 amp module. IMO, AM3 SE sounds better than AM1.
Headphones primarily tested with: FiiO EX1/Dunu Titan 1 (SE only), Etymotic ER4S (SE only), Hifiman HE-400i (SE and balanced), and Sennheiser HD700 (SE and balanced).
You’ve waited long enough by now. How does the thing sound?
Overall, the AM3 sounds neutral. It actually sounds very similar to the AM2 and AM5 in terms of a neutral overall sound signature, despite using very different chips.
AM3 presents lots of detail and has very good separation, even in SE mode. Soundstage is of moderate width (not the largest I’ve heard), but depth is very good. When all of this is combined with the rather good imaging and layering (depth perception), the AM3 presents a very coherent and convincing 3D soundstage.
Volume-Matched Comparisons
All comparisons here were conducted under volume-matching with a C-weighted SPL meter.
AM3 SE vs. AM3 Balanced
Balanced operation isn’t really going to be of much use if it doesn’t sound better than in SE implementation, right? Well, I’m glad to say that the AM3 in balanced mode clearly sounds better than when it is being run in SE.
For full-sized headphones at least, in balanced mode notes sound more airy and less constrained, and bass is better-controlled and deeper and more textured. The soundstage also gets slightly wider and deeper while separation gets noticeably better, which leads to better imaging and layering. There’s really no contest – AM3 balanced here just sounds better than AM3 SE.
Vs. AM1
The AM1 in comparison to the AM3 sounds “brighter” and a little more “metallic” and “brittle.” The AM3, in contrast, sounds somewhat “warmer” but also more natural in that notes are still as detailed without sounding like the detail is forced like AM1 can at times. AM3’s soundstage in SE is about the same width as AM1 but is slightly deeper, making for a more 3D soundstage in which it is easier to perceive depth and layering of notes. With AM3 balanced, the difference gets even bigger – the soundstage increases in width and depth yet again, making for an even more 3D soundstage. All of this can be noticed even when using easy-to-drive IEMs like the FiiO EX1 in SE mode.
AM1 also sounds a tiny bit underpowered in driving full-size headphones in comparison to AM3 SE. The difference here gets much larger with AM3 balanced. Not only do we get less grainy and strained notes, more-controlled and deeper and textured bass with AM3 balanced, but separation also seems to be somewhat better.
All in all, I definitely prefer the AM3 (even in SE mode) over the AM1 purely in terms of sound quality no matter what headphones are used. However, one has to consider the significant advantage in battery life the AM1 holds over the AM3.
Vs. AM2
First off, overall AM2 sounds very similar to AM3 in terms of soundstage size, detail retrieval, separation, imaging, etc. Perhaps AM3 is very slightly “sharper” and clearer sounding than AM2, but honestly I could just be imagining it.
As for AM3 SE vs. AM2, the AM2 is as capable as AM3 SE in powering IEMs (even more power-hungry ones). I honestly can’t tell much of a difference here.
However, for full-size headphones, AM2 actually comes out ahead. AM2, to me, simply produces less grainy notes and better-controlled and better-textured bass than AM3 SE when powering larger headphones.
But with AM3 balanced, the tables completely turn. (At least with full-size headphones, since I don’t have any balanced IEMs to test with.) Notes sound more airy and less constrained than on AM2. Bass is also deeper, more well-textured, and better-controlled. AM3 balanced’s soundstage is also slightly wider and deeper, and separation on AM3 bal. is also noticeably better (which also leads to better imaging and layering/depth perception).
So if you are planning to just use single-ended headphones, go with AM2 since it sounds just as good or better (depending on the headphone) with better battery life. But if you want to get the most out of your larger headphones, go with AM3 balanced.
Vs. AM5
First off, overall AM3 sounds very similar to AM5 in terms of soundstage size, detail retrieval, separation, imaging, etc. AM3 even sounds similar to AM5 in that they both seem to present notes that are a bit “sharper” than on AM2.
For IEM’s, you’d be hard pressed to tell any differences between AM5 and AM3 SE. However, for full-size headphones, AM5 as expected comes out ahead. AM5, to me, simply produces less grainy notes and better-controlled and better-textured bass than AM3 SE when powering larger headphones.
But what about AM5 vs. AM3 Balanced? Here, I actually prefer AM3 balanced by a bit. AM3 balanced presents a slightly wider soundstage with slightly airier notes (perhaps due to the blacker background given by balanced operation). Separation is noticeably better (more separated) on AM3 balanced than on AM5. This also means that imaging and especially layering are better on AM3 balanced than on AM5.
However, both AM5 and AM3 balanced powered my HE-400i and HD700 just as well as each other. I really couldn’t hear a difference in this respect.
Overall, I wouldn’t say you are missing out on much if you choose to take AM5 over AM3 in balanced mode. The real noticeable difference between the two is the better separation of AM3 balanced (which also leads to better layering, etc.) but otherwise they both sound as good as each other when powering larger headphones. Battery life is also similar between the two amp modules. To me there’s no doubt about it, AM3 balanced is the best. However, I would say go for AM3 if you have balanced headphones that you want to get the best out of, otherwise you will do just fine with AM5.
Tl;dr: The last sentence of this next paragraph.
At $99, the AM3 amp module is a good way to really bring out the best of your balanced headphones. In balanced mode, it sounds the best out of all of the other X7 amp modules and even has enough power for moderately power-hungry full-sized headphones. The only real major con with AM3 is that battery life takes a hit, though this is no surprise due to AM3’s capabilities. Overall, if you want to extract the best out of your headphones with the X7, look no further than the AM3 balanced module.
Thanks for reading my (somewhat) long review of the AM3 amp module!
Btw very good and detailed review. Now you just made me want to spend money on the X7 for its balanced module.
Strange it was $199 initially then moved to $99 and now it's back at $199. I know because I've been waiting to buy this and have been monitoring the price on Amazon.  
I hope Fiio fixes this soon, as I know they are currently out of AM3 stock :)