FiiO K5 PRO Review - Student-Fi!

This review is posted here in partnership with Soundnews.net . It was originally written and published by Sandu Vitalie of Soundnews.net on Aug. 28, 2019.

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Disclaimer: FiiO K5 PRO was sent to us free of charge in exchange for our honest opinion. We thank team FiiO for this opportunity.

I am an old-school guy and I like the simplest DAC/Amp units, especially desktop ones that can be wall-powered. Sadly, for the past years FiiO forget about this segment and sincerely they never had a powerful desktop solution. You might think that K3 or Q5/Q5S could be that device but they both are not really capable of driving power-hungry headphones. I still remember when K5 was released and I was impressed by its design but was a bit underwhelmed by its performance, especially with IEMs.

FiiO recently quietly announced the K5 PRO on their social media – an upgraded version of K5 with an additional DAC inside. I see the K5 PRO as an underdog, as the one that always stays in the shadow of bigger things. I still dig it and I cheer-up every time I see a new desktop DAC/Amp be announced. I can’t lie, these kinds of devices are my biggest fetish, just take a look around here, half of my articles are about exactly these types of units. You can be certain K5 PRO will get the love it deserves.

K5 PRO is a beefed-up version of K5 and a lot of things that made no sense to me on K5 (who used the 3.5mm balanced line-out please rise a hand) were replaced by cool things.

So, what exactly was changed or improved?

• Gone is the dock on top of K5, so if you wish to use your X or M series of DAPs from FiiO you will need to use the Line Input (via RCA) of K5 PRO
• Gone is the useless 3.5mm balanced line-out and instead a coaxial and an optical input made its way to K5 PRO
• The USB type-B input of K5 PRO now uses its internal DAC section
• Of course, biggest change is the internal DAC of K5 PRO (that was not present on K5) and what a DAC! It’s the newest AK4493 from AKM.
• K5 PRO is a full-blow desktop DAC, so it will decode PCM and DSD, it even has a clean Line-Out on the back in case you want to use only its internal DAC section
• K5 PRO also uses a cleaner headphone amp section, offering a lower noise (8uV compared to 10V of K5) and uses the more musical OPA 1642 JFET op-amp.

Inside the box

K5 PRO is packed in an ordinary card-board box, it isn’t too big and has thin protection foams only on front and on the back of the device.

Inside there is a bigger box that houses the external switching power supply, a power cable, a USB type-B cable with ferrites, a headphone adaptor (6.35mm or 1/4” to 3.5mm or 1/8”), a quick start guide, warranty information and additional small 4 silicon feet in case the ones applied on the device will peel off. As far as I know K5 PRO will only be offered in a black color only, K5 had a grey body.

Design & Build Quality

I find the K5 really cool looking, futuristic even, the light around the volume pot added a cool factor to it. K5 PRO looks exactly like that but instead of a simple blue light, the one on K5 PRO will tell you about the its state and bitrate: RED means it is off or that the USB connection is not established, BLUE means it is all good and that music played is 48 kHz or below, YELLOW is PCM material above 48 kHz and GREEN is for DSD material, neat.

FiiO and Hi-Res logo are of course laser engraved directly on the metallic case. Speaking about the case, it is quite thick and it is made out of aluminum that is beautifully polished and CNCed. I really like that besides anodizing it, FiiO decided to finely sandblast it, so it will be more resistant to drops or scratches.

K5 PRO has a perfect size for a desktop workstation, at only 120 x 130 x 55 mm and at about 450 grams (exactly one pound) it is quite small and can be easily integrated in any desktop rig be it at home or not.

Inputs & Outputs

Since K5 PRO can be considered a desktop class DAC and headphone amp, on its back you will find 3 digital inputs (USB, Coaxial and Optical), a RCA Line-In and a RCA Line-Out, this means than K5 PRO can be used as a DAC/Amp, as an Amp only or as a DAC only, I really like that.

On the front you have a simple input switch: Optical/Coaxial is first position, line-input is second, USB is third. It also offers a much-needed Gain switch with 3 positions: Low uses the unity-gain of 0 dB that will please the IEM users, mid gain is adding 6dB and high gain is adding 10dB.

The volume knob works also as an On/Off switch and on the far right there is your 6.35mm or ¼” headphone out. It’s really simple, just plug in a USB cable or an RCA cable, pick your input and start listening to some music.

Tech Specs & Detailed Info

FiiO already introduces to the world the newest AK4493 DAC chip in their M11 DAP, it is a really good and great performing mid-tier DAC chip, they decided to use it inside K5 PRO as well and I’m very glad they didn’t go for a cheaper alternative.

AK4493 is of course part of the Verita Velvet Sound architecture for a natural sound without any listening fatigue.

The USB input in handled by the XUF208 from XMOS, it is a well performing chip and most importantly it is very stable. I already tested multiple devices with it inside, literally tens of devices and for a good reason. I still consider XMOS to be making the best USB decoding chips of today.

XUF208 is capable of natively decoding DSD material and PCM material of up to 768 kHz at 32 bits.

What is kind of interesting is the volume wheel implementation that works in the analog domain with a digital chip, so bits of resolution will not be lost once you lower the volume down. The NJRC NJW1195 is an ultra-low noise volume adjustment chip with a -118dB of noise that will adjust the volume with steps of 0.5 dB.

Headphone amplification is handled by an OPA1642 JFET op-amp followed by the flagship TI TPA6120 op-amp for the voltage amplification and current drive.

Add an external power supply of +/- 15V and up to 1.6 Amperes and K5 PRO can provide some astonishing power output for your headphones. How much more exactly? A whopping 1.65 W of power per channel in 16 Ω and 1.5 W of power into 32 Ω, for this weight and size the power output is impressive if you ask me, more about it in a minute.

I’m really glad FiiO introduced unity gain of 0 dB (low gain setting) that should work nicely with IEMs and very sensitive headphones, the HP out is also at less than 1.2 Ω which is not that high to be concerned about.

The line-out is following the standard of 2 Vrms which is nice, THD is at a safe 0.004%, the only thing that’s not really cool is the noise floor at 8 uV or less.

As you probably guessed putting such a powerful headphone amp section meant K5 PRO to be used mostly with headphones, but in case you want it can be used with you speaker-based setup as well.

Sound Performance

I. Using K5 PRO with sensitive In-Ear-Monitors

FiiO states that the external power supply is still filtered inside the unit so the noise floor would be always in check.

I connected the FiiO’s own FA7 and later on the IKKO OH1 to check the noise floor. On the Low gain with the music paused and putting the volume at the highest setting there is zero noise whatsoever, background is as clean as it can be. If I unplug the K5 PRO from my power conditioners then there is just a faint noise on the background, but it is really faint, almost non-existing, I don’t consider it worrisome.

Switching to medium and then to high gain the noise intensifies but with its power reserve, low gain is enough even for desktop class headphones. IEM users should never use more than the low gain setting, even multidriver IEM designs would be Ok with low gain.

To put into perspective how it compares to other units, the noise with IEMs is about on the same level with the Headamp Gilmore Lite Mk2, it is a bit higher than that of Aune S6 PRO and S7 PRO, lower than that of Burson Play and Playmate and much lower than that of xDuoo TA-10. Hell, it is even lower than that of KECES S3.

Of course, once I press play the noise is nowhere to be found and a black background will appear in front of me. Listening to it for a week or so it reminded me so much of a device that I really adored: the $600 Aune S6 Pro. These two units are sounding close to each other but of course K5 Pro is not as refined, not as clean and not as wide sounding but the overall tonality is the same.

On a close inspection it seems that both use AKM DAC chips and TPA6120 for headphone amp duties. To me K5 PRO revealed that naturalness, flow and musicality can be also had for a much lower cost.

I’m on a listening spree with Tool as they just hit streaming services. Listening to Tool - Ænima on the FA7 I’ve heard a very good liquidity, the flow was very reminiscent of their M11 DAP, you just don’t want to stop from listening. The AKM Velvet Sound is very obvious as K5 PRO is completely opposed to digitus and is free of any harshness.

What made my head turn was the slam and control K5 Pro had with IEMs. If you are an avid IEM listener it will impress in terms of tactility, texture and in the slam department. FA7 are awakened to something else, they are sounding quite different on portables. FA7 started sounding jumpy and a bit hysterical, especially on fast punchy music. The bass notes were more prominent, the notes carried more air and the impact was more impressive.

I then moved to some Balkan music where lots and lots of instruments are hitting me from different angles, this is basically the perfect layering and staging tests I could think of. First of foremost K5 PRO is not mixing all those together in a big blob of sounds but mostly puts them away from each other. I would not characterize it as having a really wide soundstage or as very airy sounding. I believe it has a medium sized soundstage with more than decent airiness. What’s important is that K5 Pro is not forward sounding and cares about your layering, so muddiness will never be spotted. If metal is your thing, of course nothing can cure that distortion, muddiness and loudness… so yeah, K5 PRO can’t cure cancer.

II. Using K5 PRO with full-sized headphones

K5 PRO is having a hard task ahead, David will meet two Goliaths as it will try do drive two planar-magnetic headphones, the Quad ERA-1 and the inefficient Hifiman Arya.

Of course, gain was set on high but due to low sensitivity and high impedance, the noise-floor can’t be spotted even at close to maximum volume. Any music I would listen to, the background would always be silent as night and will leave music breathing and enveloping my head.

I resumed my listening session with some local folk rock (sorry can’t help myself) and with the Quad Era-1 not a lot of time passed and I was already tapping my right foot, a sign that the overall performance is pleasing and engaging.

Quads didn’t transform into something else, how FA7 IEMs did, they sounded as I remember them: very dynamic, explosive and striking without mercy when asked for.

The same medium-sized soundstage remained and I was pleased to hear a very engaging and dynamic performance. From my point of view, Quad ERA-1 doesn’t need more power than this, at about 50% it was already loud and at 60% it was already too loud. The more I listen to K5 PRO the more I realize it goes mostly towards a musical and engaging sound and not a lot to the technical and super linear side of things. With K5 PRO, I don’t want to review it and write my impressions down, I just want to listen to some music and have some quality time.

If K5 PRO can easily drive the Quads, you can include all the dynamic headphones in this list as well, the Sennheiser HD660S at half volume were already sounding like speakers, so draw your conclusions.

Now, Hifiman Arya is a different, much bigger beast. With it my volume would normally sit at 1 to 2 o’clock (about 60 to 65 % volume) and I could go maximum to 3 o’clock (75% volume) for a head-bang inducing, neck-pain relieving performance.

Dynamics were there, slam was there, nothing sounded crowded or up-front, Arya were driven nicely with it. Actually, they were driven much nicer than the more expensive offerings like the Headamp Gilmore Lite Mk2 or Aune S6 Pro. K5 Pro has a lot of power and that can be easily spotted, I still had some power left on tap with Arya, that is a very good sign!

Since Hifiman Arya is a reference sounding headphone with a close to perfect linearity and with a wide spread soundstage I could put K5 PRO under its magnifying glass.

Moving on to the frequency response I can say that K5 PRO is just a bit rounded in the treble area and just a tiny bit in the sub-bass area.

Listening to usual bass tracks revealed that it loses close to zero sub-bass information. So, all my electronica tracks sounded as impressive and as engaging as I remember them on my big rig. With Hifiman Arya I was losing maybe 1 to 2 dB of sub-bass information compared to my reference setup, but that can be hardly spotted and as I previously said every electronica track sounded as impressive and hard hitting. Yeah, sub-bass is close to being perfect, but it doesn’t want to or need to be so.

Mid-bass sounded linear and defined, very present as well, among the best parts of K5 PRO for sure. I can’t fault anything in terms of mid-bass, it sounds clean, quite detailed and layered. Yes, I even spotted multiple layers of it so all in all if you care about bass, K5 PRO will render it nicely without overdoing it to bass-head levels.

The transition to lower midrange is done smoothly without a single drop, all in all I believe the midrange is absolutely the best part of it and for good reasons. AKM chipsets were always impressive in the midrange department. Vocal performance is impressive, all the pipes and string-based instruments had a longer vibration and a lower center of gravity. I really enjoyed my time listening to some acoustic music as K5 PRO is putting a small emphasis on each musical instrument, it is what it does best.

K5 PRO has a meaty tone and a natural timbre, add a longer vibration of the midrange and you could imagine its performance.

Moving on to the treble region, K5 PRO is almost like a chameleon, sometimes the cymbals and hi-hats are really detailed and pushed on the same level with the rest, sometimes it rolls-off them a bit for a natural presentation. What was clear to me is that treble intensive tracks will still have a lot of presence in this area but without the aggressivity. Ah, speaking about it, aggressivity will never be present on K5 Pro, it just can’t be spotted. This little fellow is close to neutrality and choses to be a good boy instead of an aggressive one. Teeth clenching music will sound easier and more bearable on it.

Detail retrieval is good, but since K5 PRO is not boosting the sub-sonic treble area you have the (fake) impression that it has a lower clarity and it doesn’t sound as detailed. Firing some Hi-Res and DSD material showed some pretty good detail retrieval and on the right music it will be certainly spotted. It is good but not great, the higher priced offerings will have more of it.

Depth and imaging are certainly good and better than a lot of ESS Sabre based DAC/Amp units I tested of late. I consider that it sounds quite deep, with my eyes closed I can certainly tell I have a longer distance to one note and a shorter to another one. It is not super-decompressed as more expensive units are sounding but it is not neither up-front or boring. With both my planars slam was good, of course not the best I’ve heard but at $150 it slammed like crazy, especially my IEMs were shaken by it.

Comparisons

FiiO K5 PRO ($159 USD) VS Loxjie D20 ($240)

D20 is a bit bigger, heavier, uses a tiny screen on the front panel to show some important information. It also uses a more advanced AK4497 chip but a much weaker headphone amp section. D20 uses a toroidal transformer for a better power filtering, K5 PRO relies on an external switching power supply.

If headphone listening is your first priority then K5 PRO kicks the hell out of D20. It has much more power on tap (1.5 W versus 0.22W on 32 Ω) and as a result will sound livelier, more dynamic, will slam better and overall will sound much more engaging. K5 PRO can basically drive anything you want, by comparison D20 will struggle even with some multidriver IEMs.

K5 PRO will also sound more expansive, airier and will unleash the potential of your headphones. D20 has a rolled-off performance, sub-bass and upper-treble are hardly spotted and with headphones it is far from neutral sounding.

If I move my listening session to the living room then D20 with its superior DAC chip and power filtering will sound better with my speakers. It sounds a tad wider, more spacious and slightly more focused with the KEF LS50W. D20 will also push forward the detail retravel and will reveal just a bit more nuance and detail, a really nice pairing with my speakers. What is kind of weird is that D20 doesn’t sound rolled-off with speakers and actually carries more treble information than the FiiO. K5 PRO is not much worse, but lags behind for sure.

Conclusion

I’m so glad FiiO didn’t forget their old customers that are still shopping for desktop DAC/Amp units. At last those people have an upgrade path, if you are still using an older E07K, E17K, E18, then I think I found your replacement. Even K3 users will see a big appeal in the K5 PRO with its robust build and easy to like sound performance.

Build quality wise there is nothing to complain about: it’s black, it’s entirely metal made and looks futuristic on any desk.

Sonically, as a DAC and headphone amp combo it kicked ass even with hard to drive planars and drove those to ear-bleeding levels. IEM users are blessed with unity gain at 0 dB (low gain) that made wonders with my IEMs and if you are craving for some hard-hitting slam, K5 PRO will deliver that to any multidriver IEM.

Can you ask for more at ~$159? I personally can’t and if you are on a low-budget and headphone listening is important to you, then I consider it the best current production student-fi DAC/Amp combo.

I recommend getting it from here (Apos is offering free shipping in the USA, free 30-day returns in case you don’t like it, an extra 1 year of warranty and lowest price guarantee).

PROS:

• Beautiful, clean design without rough edges
• Has a natural sound signature
• Engaging and lively sounding, good slam
• Great balance between technical and musical
• Decent sized stage, deep sounding as well
• Decent detail retrieval, sounds clean as well
• Clean headphone out section
• Lots of power on tap
• Has an impressive value

CONS:

• No more Infinity Sound? (balanced headphone out)

ASSOCIATED EQUIPMENT:

• DACs: FiiO K5 PRO, Q5S, Matrix Audio Element X, KECES S3, Burson Swing
• DAPs: FiiO M5, M6, M3K
• Headphone amps: Benchmark HPA4, Aune S7 PRO, Erzetich Bacillus, Headamp Gilmore Lite Mk2
• IEMs: FiiO FA7, IKKO OH1
• True Wireless headphones: Creative Outlier Air, Hifiman TWS600
• Full-sized headphones: Hifiman Arya, Quad ERA-1, Sennheiser HD660S
• Wireless headphones: Master&Dynamic MW65
• Loudspeakers: KEF LS50W
• Interconnects: QED Reference XLR, Aune AL3 XLR
• Power Cables: Isotek EVO3 Premier
• Balanced Power Conditioners: PLiXiR Elite BAC 400, KECES BP-600