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INTRODUCTION

 
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 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, and the AM2 module in February.
 
For my full review of the X7 go here, and of the AM2 go here. And 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 the AM2 medium power module, and now the AM5 high power module, those with harder to drive cans now have choice for the power they may be looking for.
 
ABOUT FIIO
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.
 
FiiO’s products have followed a very simple formula since 2007 – affordable, stylish, well built, functional, measuring well, and most importantly sounding good.
 
DISCLAIMER
The X7 and add on AM5 module were provided to me gratis as a review samples. I have made it clear to FiiO that I still regard any product they send me as their sole property and available for return any time at their request. But I thank them for the ability to continue use of the X7 – both for follow up comparisons and also for my own personal use. It is still my intention to purchase the X7 from FiiO at some stage in the future.
 
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. 
 
PREAMBLE - 'ABOUT ME'.

Spoiler: Click here for a summary of my known preferences and bias

REGARDING THE X7
This review is essentially about the AM5 high power 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. For information regarding the AM2 module you can ready my review or the other one listed by Alex (Twister6)
 
This is a purely subjective review of the AM5 high-power 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.

THE REVIEW

PACKAGING AND ACCESSORIES
The AM5 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 AM5 module attached and some text telling you that this is the AM5 amplifier module. On the rear of the box are QR codes which will take you to FiiO’s website or Facebook page.
 

Front of the retail box	Rear of the retail box	Inner metal container

 
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 AM5 module nestled safely inside.
 
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.
 

The FiiO envelope containing the accessories	Full package including the AM5	My modified container for the amp modules

 
As far as the AM5 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 module, and this includes the lack of specifications on the packaging. The good thing is that FiiO have already listed the specs for the AM5 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 above).
 
TECHNICAL SPECIFICATIONS
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 module.
 

	AM5 Module	AM2 Module	AM1 Module
Dimensions	~ 64 x 25 x 16mm	~ 64 x 25 x 16mm	~ 64 x 25 x 16mm
Weight	32g	32g	29g
Voltage amplification	Muses02	Muses02	OPA1612
Current Drive	TPA6120 A2	Buf634	AD8397
S/N (H/O)	≥120 dB (A-Weight)	≥118 dB (A-Weight)	≥115 dB (A-Weight)
THD+N (H/O)	<0.001% (32Ω/1 kHz)	<0.001% (32Ω/1 kHz)	<0.0008% (32Ω/1 kHz)
Output into 16 ohms	>800 mW (16Ω/1 kHz)	>350 mW (16Ω/1 kHz)	>200 mW (16Ω/1 kHz)
Output into 32 ohms	>500 mW (32Ω/1 kHz)	>300 mW (32Ω/1 kHz)	>100 mW (32Ω/1 kHz)
Output into 300 ohms	>55 mW (300Ω/1 kHz)	>30 mW (300Ω/1 kHz)	>10 mW (300Ω/1 kHz)
H/O impedance	<0.5 Ω (32Ω)	<0.5 Ω (32Ω)	<0.2 Ω (32Ω)
Peak output voltage	>11 Vp-p	>8.8 Vp-p	>5.2 Vp-p
Peak output current	>250 mA	>250 mA	>250 mA
Channel Separation	>72 dB (32Ω/1 kHz)	>72 dB (32Ω/1 kHz)	>73 dB (32Ω/1 kHz)
Play time	6 hours+	8 hours+	9 hours+

 
BUILD / DESIGN
 

Front and bottom of the AM5 including ports	Back and bottom of the AM5	Internal connector

 
Again not much to talk about here – the AM5 has the same dimensions as the AM1 and AM2, and the main differences are internal, but also in their exterior colouring. Where the AM1 has a brushed titanium appearance on the front and powdered titanium appearance on the rear, the AM2 and AM5 are both slightly darker shades, and powdered finished on both front and back. Otherwise they all look and feel identical. The AM2 and AM5 colouring appears to be the same. There is white text on the back of each designating the model number.
 

AM5, AM2 and AM1 - with cap, hex screwdriver and screws	AM5, AM2 and AM1	AM5, AM2 and AM1

 
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 AM5 is perfectly flush, and the only thing very apparent with the AM5 fitted is the change in colour (compared to X7). This of course disappears when used with the cover.
 

Expanded schematics, courtesy of FiiO	X7 with AM5 (front)	X7 with AM5 (rear)

 
DESIGN – INTERNALS
Although you can’t see them, it is probably a good idea to mention the internal electronics. Where the AM1 uses an OPA1612 for voltage and AD8397 for current, and the AM2 uses the Muses02 and Buf634, the AM5 this time uses a combination of the Muses02 along with the Texus Instruments TPA6120 A2. All have impressive measurements for distortion, SNR, output impedance and channel separation. The biggest difference is really the voltage output, and power delivery. As far as power goes, the AM5 is able to produce more than five times the output of the AM1 into 300 ohms, and almost double the output of the AM2 medium power module. It also has a higher peak voltage output.
 
POWER OUTPUT – REAL WORLD
So the specs are listed above, bit what does that mean in the real world? The obvious test was going to be with my HD600, so armed with a 1 kHz test tone, and my trusty calibrated SPL meter, I set about volume matching. To aid quick swapping in this exercise, I simply undid the screws, and left them off – so I could easily slight amp module in place, and then quickly swap as I needed to. The SPL meter was left in a fixed position, and comparative measures taken were (with the 300ohm HD600 – I couldn't get the cups fully sealed – but close enough):
AM1 at 77/120 = AM2 at 66/120 = AM5 at 66/120
AM1 at 86/120 = AM2 at 75/120 = AM5 at 71/120
 
All the above were within 0.2 dB. I then used those measurements playing actual music and recording maximum peaks – and again all were within 0.2 dB. 
 
I also checked the SPL level at max volume from the X7 (120/120) and measured 93.8 dB (AM1), 99.4 dB (AM2) and 99.7 dB (AM5) respectively (A-weighted). So what does all of this mean and why isn't the AM5 showing double the volume? Well simply because the AM2 is able to drive the HD600 pretty well, it isn't exactly a difficult load, and the extra power on tap simply isn't gaining anything. Or is it? The thing we haven't taken into account is peak voltage, and the HD600 is a headphone which subjectively seems to respond to more voltage than current. I should also note that all 3 amp modules supply the same current peak current (250 mA) so maybe this is why the volume appears to have reached its limit in my set-up?
 
Please note – I didn't bother testing IEMs in this scenario as nothing I have requires a high power module. And I also did not check hiss as it is the same output impedance as the AM2, and also because the general use of this module will be fore higher impedance, lower sensitivity headphones, so hiss won't be an issue.
 
BATTERY LIFE
Although FiiO publishes their own real world tests with their modules, I also like to conduct my own. Using the HD600 with a volume of 80/120 I'd managed 9 hours and 42 minutes life, the AM2 module at 70/120 managed 8 hours and 49 minutes, and the AM5 module at 70/120 managed 6 hours and 29 minutes.
 
This was with the screen off most of the time, and continuous music playing. The level of 70/120 would give me 65-70 dB average listening volume which actually ties in nicely with my normal listening levels. I should also mention I was using low gain on the X7 with all 3 tests.
 
Of course this will also be dependent on what else you have running, what headphones you are driving, and also if you are using Wi-Fi, Blue-tooth, or using the screen a lot.
 
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 - http://www.head-fi.org/a/brookos-test-tracks and concentrated mainly on tracks exposing detail, dynamic contrast, sound-stage, bass quantity and vocal quality. This is just a comparison between AM2 and AM5 as the AM1 (whilst is is capable of driving an HD600) is probably more suited to IEMs and portables.
 
Remember this is pretty subjective!
 
With the HD600
My first test was sound staging (Amber Rubarth – Tundra). If there is any difference in stage it is very slight, and tends to favour the AM5 just a little in depth and width (really small differences). This could be in the very slight tonality change – in my critical listening I've already found that the AM2 is just a slight hint warmer than the AM5 with the HD600. The AM5 is to me just a hint more vivid / dynamic.
 
With the bass test the feeling continued – so much so that I had to recheck volume. Nope – still matched. The AM2 just seems little flatter and warmer, maybe a little more relaxed. The AM5 in comparison is a bit more dynamic, more raw and more vivid. I'm not sure if this is the added voltage or simply the tonality difference between the BUF634 and TPA6120 A2, and to be honest I don't care. I really like the pairing of the HD600 with the AM5, and I'm pretty sure I could pick it blind. The two modules are visually identical, and I've been losing track of which is which sometimes, so without looking at the screen I've been guessing and haven't had it wrong yet.
 
Switching to vocal tracks and its close between the two (they both sound really excellent actually), but I'm still in the AM5 camp. Female vocals still have that slightly more dynamic presence, and there is a little more bass slam with some of my rock. It's really hard to describe overall, but the more I listen the more it is apparent.
 
If anyone has the X5 original and X5ii they'll know what I mean. The X5 original was every bit as refined and had the same detail as the X5ii, but the difference was in the presentation. The X5 was very neutral, and slightly flat. The X5ii was a lot more dynamic – it sort of takes you along for the ride.
 
With the T1
So how does the AM5 do with the 600 ohm  Beyer T1? Well for starters, at around 80/120 on low gain it's easily getting me my usual listening level of around 70 dB with peaks toward 80 dB. And I'm also noticing the same differences I had with the HD600. Slightly more dynamic and vivid presentation, maybe a bit more holographic in presentation of stage. The differences are small, but if I'm listening to full sized cans, there is no question – I'd be grabbing the AM5 despite the reduced battery life.
 
GRAPHS
Like last time, the last thing I did before the final edit was to hook the X7 up as DAC on my PC, and record the output under loop-back to see how well the overall measurements were on frequency response. Again the one thing I need to stress here is the roll-off in the top end is the filter set-up on the X7 DAC section.
 

AM1 vs AM2 and AM5.  E17K (green) included for reference	Same graph with scale magnified

 
You’ll see the three curves for AM1, AM2 and AM5 are practically identical. The roll-off you're seeing there is the filter on the DAC, and just so people aren't alarmed, I've seen the same on the all the FiiOdevices with DACs engaged (the exception being the E17K), and also the Luxury & Precision LP5 which is the most expensive (and one of the best sounding) DAP/DACs in my possession. If you want to have a look at this graphically, check out the very bottom of my AM2 review.
 
So this tells us that all 3 amps are pretty linear, and that the output of the AM5 under loop-back is actually really close to the output of the AM2 – and it also confirms the close to 6 dB difference between AM1 and AM5 we recorded earlier using the HD600. 
 
COMPARISON
I was pretty happy with the output of the X7 + AM5 combo with the HD600. So happy in fact that I thought it might be pretty close in SQ to the aforementioned Luxury & Precision LP5 – a USD 1300 DAP which is easily the best sounding DAP I've ever heard with full-sized headphones.
 
So I volume matched both devices with test tones with the HD600 (this is not easy to do – but the meter shows I'm within about 0.2 dB, and they sound exactly the same volume when I'm switching). I then queued the same album and set both devices playing continuously (used adaptors so they wouldn't stop when I unplugged). I could then rapidly switch mid-song and essentially get continuity with bothdevices.
 
 
I chose Sarah Jarosz album “Build Me Up From Bones” because it has such wonderful tonality with the HD600, and also because there is some quite high level detail woven throughout.Now this testing isn't blind – so it's highly prejudiced – and I expected the X7 to come close, but ultimately the LP5 to win out (because it really is one of the most complete sounding DAPs I've ever heard with higher impedanceheadphones). To give you an idea of how good the LP5 is with the HD600 – it rivals my iDSD with or without a very good tube amp in tow.
 
I didn't see this one coming – they sound so similar now, that I'd be hard pushed to tell them apart. There is the slightest bit of further depth with LP5 – but it is so minor as to not matter (to me anyway). And that is probably the easiest way to sum up the AM5. It isn't just good with the X7 and HD600 – it is spectacular. I can't believe this $650 player and $100ish add-on module are now combining to be one of the best set-ups I've heard.

CONCLUSION

This will be pretty short and sweet, as I’ve pretty much already summarised everything – but once again to put it in a couple of sentences …..
 
The AM5 module (like the AM1 and AM2) has a great build, is easy to fit, and measures as well as it sounds. It will cost you some battery life, but it easily handles both my HD600 and T1 with headroom to spare. Paired with a headphone like the HD600 it is quite simply one of the best combinations I've personally heard, and I'd put it in the same league as the Luxury and Precision LP5 (if not an equal, then at least playing in the same ballpark).
 
At an approximate release price of USD 99.00 there is nothing I can think of which makes me hesitate at all in recommending it. If you already have an X7 and want to take your higher impedance cans to another level, I simply cannot recommend this amplifier module enough.
 
When I eventually have the funds to purchase the review X7 from FiiO, the AM5 will automatically be the next purchase.
 
FINAL THANKS
Once again thanks to Sunny at FiiO for giving me a chance to try the AM5 before its global release.
 

X7 + AM5 is simply an amazing match	and even rivals the LP5