Home Amps/DACS FiiO K9 Pro Review – There’s A New Sheriff In Town

FiiO K9 Pro Review – There’s A New Sheriff In Town

The K9 Pro shoots for the moon and pretty much lands on it

by Stuart Charles Black
FiiO K9 Pro Review

Don't forget to share if you found it helpful!

Originally published 1/31/22.

  • Updates: 5/3/22. ESS version impressions and comparison to the AKM version.

Big thank you to Apos for sending this review unit! This review will cover both the K9 Pro AKM and ESS versions.

Before we get started, check out Apos Audio. They are a great up-and-coming distributor with a phenomenal-looking website and excellent customer service. They also offer free shipping, the lowest price guarantee, a 2-year warranty, and a 45-day return.

So, after demoing 55+ Amps & DACS covering the span of about 4 years, I can safely say FiiO’s K9 Pro provides the most value at the most sensible price (given what it can do) and is without a doubt the most versatile unit I’ve tried. I absolutely recommend it wholeheartedly and you’ll find out exactly why in this extensive review.

Greetings mate and Welcome aboard.

Stuart Charles here, HomeStudioBasics.com helping YOU make sound decisions leading to a beautiful audio experience that will make you fall in love with music (NOT gear), all over again, so…

Video Discussion

Don’t forget to leave me some love and subscribe! <3

At A Glance

FiiO K9 Pro Amplifier High Resolution Desktop DAC Headphone Amps THX-AAA 788+/Support 384 kHz/Native DSD256/MQA Decoding/LDAC/AptX Adaptive/AptX HD
FiiO K9 Pro Amplifier High Resolution Desktop DAC Headphone Amps THX-AAA 788+/Support 384 kHz/Native DSD256/MQA Decoding/LDAC/AptX Adaptive/AptX HD
Max Sample Rate/Resolution
384kHz / 32-Bit (DSD256)
2x RCA Unbalanced, 1x 4.4mm TRS, 1x Coaxial, USB Type-B, Bluetooth S/PDIF, 1x TOSLINK Optical S/PDIF
2x RCA Unbalanced, 2x XLR 3-pin Balanced,
Headphone Outputs
1/4" Unbalanced, XLR 4-pin Balanced, 4.4mm Balanced
Power Output
1/4": 278mW @ 300 Ohms, XLR 4-pin: 278mW @ 300 Ohms, 4.4mm: 1.1W @ 300 Ohms
Output Impedance
< 1 Ohms (32-Ohm Load)
6.2 lb / 2.8kg
Price not available
Learn More
FiiO K9 Pro Amplifier High Resolution Desktop DAC Headphone Amps THX-AAA 788+/Support 384 kHz/Native DSD256/MQA Decoding/LDAC/AptX Adaptive/AptX HD
FiiO K9 Pro Amplifier High Resolution Desktop DAC Headphone Amps THX-AAA 788+/Support 384 kHz/Native DSD256/MQA Decoding/LDAC/AptX Adaptive/AptX HD
Max Sample Rate/Resolution
384kHz / 32-Bit (DSD256)
2x RCA Unbalanced, 1x 4.4mm TRS, 1x Coaxial, USB Type-B, Bluetooth S/PDIF, 1x TOSLINK Optical S/PDIF
2x RCA Unbalanced, 2x XLR 3-pin Balanced,
Headphone Outputs
1/4" Unbalanced, XLR 4-pin Balanced, 4.4mm Balanced
Power Output
1/4": 278mW @ 300 Ohms, XLR 4-pin: 278mW @ 300 Ohms, 4.4mm: 1.1W @ 300 Ohms
Output Impedance
< 1 Ohms (32-Ohm Load)
6.2 lb / 2.8kg
Price not available
Learn More

In The Box

FiiO K9 Pro Amp/DAC

USB Type-A to Type-B Cable

Power Cable

Bluetooth Antenna

1/4″ Headphone Adapter

Quick Start Guide

Warranty Card

FiiO K9 Pro Review

FiiO K9 Pro Review


I think it’s safe to say that FiiO and quality go hand in hand.

Sure, they have a few minor issues that need to be ironed out (namely a sometimes sluggish Bluetooth response), but by and large, investing in their products is a safe bet and I’ve never had anything they’ve sent break down on me or cease to function dating back to 2018.

The only other company I’ve had more experience with is iFi, but both are synonymous with reliability and an overall fantastic value.

The K9 Pro is no different.

In fact, this thing may end up replacing almost every recommendation I have on this site with regard to Amps and DACS and this article could be the most important piece I’ve ever written on the subject.

So definitely stick around as we’re going to cover all bases today. It will be long, but by the time you’re done reading, you shouldn’t have a doubt in your mind whether or not FiiO’s flagship Amp/DAC is for you.

We’ll cover everything from Gaming/Film, Bluetooth, Desktop Listening, Speaker pairing, Vinyl, Balanced, Unbalanced, and everything in between.

So let’s get rolling!


  • Price: Check Amazon! | Check Apos! | Check B&H!
  • Form Factor: Table Top
  • Converter Type: D/A
  • Number of Channels: 2
  • Conversion Formats: S/PDIF (Coaxial), S/PDIF (Optical), TOSLINK
  • Converter Circuitry: A/D Chipset:
    1 x AKM AK4499
    1 x XMOS XUF208
  • Display: None
  • Max Sample Rate/Resolution: 384kHz / 32-Bit (DSD256)

Analog Audio I/O

  • 2 x RCA Coaxial Unbalanced Line Input
  • 1 x 4.4 mm TRS Balanced Line Input
  • 2 x XLR 3-Pin Balanced Line Output
  • 1 x 1/4″ TRS Unbalanced Headphone Output (Front Panel)
  • 1 x XLR 4-Pin Balanced Headphone Output (Front Panel)
  • 1 x 4.4 mm TRS Balanced Headphone Output (Front Panel)

Digital Audio I/O

  • 1 x RCA Coaxial S/PDIF Input
  • 1 x TOSLINK Optical S/PDIF Input


  • Host Connection / USB: 1 x USB Type-B
  • USB (Non-Host): 1 x USB Type-C
  • Wireless Connectivity: Bluetooth (Audio Streaming, Mobile App)


  • Frequency Response: 20 Hz to 20 kHz

Max Output Level

  • XLR Line Outputs:
    +5 Vrms
  • RCA Line Outputs:
    +2.5 Vrms
  • 1/4″ Headphone Outputs:
    +26 V p-p
  • 4.4 mm Balanced Headphone Outputs:
    +51 V p-p
  • XLR Balanced Headphone Outputs:
    +51 V p-p

Headphone Output Power & Output Impedance

  • 1/4″: 1.1 W into 16 Ohms
  • 1/4″: 2 W into 32 Ohms
  • 1/4″: 278 mW into 300 Ohms
  • XLR 4-Pin: 1.1 W into 16 Ohms
  • XLR 4-Pin: 2 W into 32 Ohms
  • XLR 4-Pin: 278 mW into 300 Ohms
  • 4.4 mm: 1.1 W into 16 Ohms
  • 4.4 mm: 2 W into 32 Ohms
  • 4.4 mm: 1.1 W into 300 Ohms
  • Output Impedance: < 1 Ohms (32-Ohm Load)


  • RCA Line Outputs:
    ≥ 123 dB (A-Weighted)
  • XLR Line Outputs:
    ≥ 128 dB (A-Weighted)
  • 1/4″ Headphone Outputs:
    ≥ 123 dB (A-Weighted)
  • XLR Balanced Headphone Outputs:
    ≥ 123 dB (A-Weighted)
  • 4.4 mm Balanced Headphone Outputs:
    ≥ 123 dB (A-Weighted)


  • RCA Line Outputs:
    < 0.0007%
    XLR Line Outputs:
    < 0.0004%
    1/4″ Headphone Outputs:
    XLR Balanced Headphone Outputs:
    < 0.0004%
    4.4 mm Balanced Headphone Outputs:
    < 0.0004%


  • RCA Analog/Line Outputs:
    ≥ 110 dB (1 kHz, 10 kHz)
  • XLR Analog/Line:
    ≥ 123 dB (1 kHz, 10 kHz)
  • 1/4″ Analog/Headphone Outputs:
    ≥ 75 dB (1 kHz, 32-Ohm Load)
  • XLR Analog/Balanced Headphone Outputs:
    ≥ 114 dB (1 kHz)
  • 4.4 mm Analog/Balanced Headphone Outputs:
    ≥ 114 dB (1 kHz)

Digital Audio

Sample Rates

  • TOSLINK Optical S/PDIF Inputs:
    Up to 96 kHz
  • Coaxial S/PDIF Inputs:
    Up to 192 kHz
  • USB Inputs:
    Up to 384 kHz (DSD)
  • Bit Depth: Up to 32-bit
  • Digital Audio Decoding: DSD


  • Power Requirements: AC Input
  • AC Input Power: 110 to 230 VAC, 50/60 Hz


  • Dimensions: 8.9 x 7.9 x 3″ / 22.5 x 20 x 7.6 cm
  • Weight: 6.2 lb / 2.8 kg

Packaging Info

  • Package Weight: 9.465 lbs.
  • Box Dimensions (LxWxH): 14.1 x 13 x 6.2″

Wow, now that we’ve written out enough specs to fill out a book as thick as the Patriot Act, let’s talk about the literal Elephant in the room.

That’s right, I’m referring to this Super Mutant Behemoth Amp/DAC roughly the size of Big Pun.

It’s almost as if the folks over at FiiO sat down one day, surveyed the current market of do-all Amp/DACS, and decided to one-up everybody like Scarface.

Well, one-up everyone they have, bass heads.


Because when I tell you this thing is capable of anything, I pretty much mean anything. 😉

Remember how I said the K5 Pro was like a lean soccer player with some muscle?

Yeah, forget I said that.

The K9 Pro makes the K5 Pro look like an anorexic runner on a diet of Rice Cakes and Powerade. This thing should have its own area code. I mean, it has everything else.

If it were a bodybuilder, it would be Arnold Sch… no. It would be Ronnie Coleman at the height of his meathead days.

In fact, I was expecting it in the mail and still had no idea what it was when I pulled it out of the locker in my apt. complex. The freaking box weighs over 9 lbs. NINE.

“Did I order dumbells?” I thought nervously to myself.

“No, I have a gym membership, why would I order dumbells.”

Opening the box was almost like that scene in Pulp Fiction when Vincent opens the stolen briefcase.

“Are we good? Vincent?”

“Oh, we’re good.”

You think I’m kidding, but it’s the first time I’ve ever put on GLOVES before handling an Amp.

That’s right, you heard me correctly. I refuse to dirty up this beautiful piece of hardware with my grubby pawprints.

Design & Aesthetic

Make no mistake, this is a beautifully elegant unit but doesn’t unnecessarily draw attention to itself (I know, it’s hard to believe).

As much as I just joked about it, it’s sleek, utilitarian, and unassuming.

On the bottom are 4 built-in rubber feet which are to be expected at this price point. Everything about it feels premium and high-class.

Update: The ESS version comes with separate rubber feet that stick on.

The amp does occupy a rather large footprint, so plan your space accordingly. For instance, it’s so big that I can’t just do a simple reach around to flick the On/Off switch given my setup. It barely fits in the space I have.

No, I have to physically turn it a little in order to get my finger back there.


This all-aluminum anodized black chassis has been finely sandblasted and does look and feel rather luxurious without really resembling what it actually is – an incredibly hefty and robust piece of hardware that could honestly be in the Guinness book of world records.

I was truly impressed with the craftsmanship here and there’s not a doubt in my mind you will be as well.

Let’s take a look at everything it can do. We’ll discuss the sound profile as well as its ultimate value, so don’t fret.

FiiO K9 Pro Review


Note: From here on out, the review will focus on the AKM version with a comparison to the ESS one towards the end.

The K9 Pro is equipped with the AK4499 DAC Chip and supports up to 384kHz and native DSD256. What Is DSD In Audio?

If you’re familiar with the AKM facility fire, you’ll know that these chips have been pretty scarce for the last couple of years, which is just another reason to add to the list of many why you should consider investing in this thing.

The K9 Pro also utilizes the THX AAA 788+ module which supposedly provides exemplary detail and dynamics according to FiiO.

I’m a bit wary of recommending DACS based on the THX stamp, but your mileage may vary. Related: What is THX AAA Technology In Audio & Video?

Fully Differential Design

Without getting overly technical, the main purpose of a fully differential amplifier is to suppress noise.

A lot of the terminology and math used to describe this technology is admittedly way over my head, but in short, you can expect the following benefits from a fully differential amplifier such as the one utilized in the K9 Pro:

  • Improved voltage swing. Both signals are out of phase, and the dynamic range is two times more than a single-ended output with the same voltage swing.
  • Noise immunity. Since a differential signal is a difference between two single-ended signals that are out of phase to each other, any common-mode disturbance, power-supply noise, ground disturbance or electromagnetic interference will affect both signals equally – and ideally cancel each other out.
  • Reduced harmonic distortion. Theoretical analysis of the distortion products of the differential output signal results in an even-order term cancellation. In reality, the distortion is also strongly dependent on the board layout and measurement setup.

These sentiments are echoed by FiiO themselves:

“Fully differential signals go through the four-channel DAC, four-channel volume adjustment, and four-channel amp for a truly balanced design. Such a design ensures minimal interference between different components in order to fully maintain all details and large dynamic swings in music for unmatched sound quality.”FiiO

FiiO K9 Pro Review

I like to think of a fully differential amplifier as something similar to the concept of a simple balanced design that ultimately uses reverse polarity to cancel out the noise or interference that may run down the wires.

While I think most of the selling points on FiiO’s website can be boiled down to “It’s clean”, I do think its Asynchronous nature is important even though you may or may not actually hear a difference.

I like to say that I can perceive a subtle one, but your mileage may vary. What is Asynchronous USB? | Do You NEED It?

The K9 Pro also utilizes what’s known as dual-mode clock management technology.

Dual femtosecond clocks of excellence

The newest generation of XMOS chips supports dual-mode clock management technology. Under USB and Bluetooth decoding, dual asynchronous femtosecond clocks are used, while under optical and coaxial decoding, automatic PLL clocks are employed. A more precise clock management system makes it easier to handle any kind of source and maintain the maximum quality possible. FiiO

In any event, the K9 Pro has you covered. We’ll get into specifics of its versatility in a bit.

Front Panel

The all-aluminum alloy front contains a whopping 3 different headphone outputs including 4-pin XLR, Balanced 4.4mm, and 1/4″ Single-ended.

In the middle is your Gigantic Stainless Steel Volume Potentiometer that makes the K5 Pro’s look like something you’d find in Toys-R-Us.

It feels pretty incredible to the touch, and as much as I joke about audiophiles and their obsession with gear, this thing kind of almost puts me squarely back into that camp. Almost.

I’m so excited, and I just can’t hide it.

There are RGB indicator lights surrounding the volume knob that vary in color depending on the sample rate.

  • Blue = 44.1kHz
  • Yellow = Anything over 48kHz
  • Green = DSD

When the unit is idle, the colors will cycle. For instance, pressing pause initiates these color changes and they range from Green, Red, Yellow, White, Cyan, Blue, Magenta, etc.

The metal input switches and input buttons are super easy and intuitive to use as well, as I can go from listening on my PreSonus Eris e3.5s back to headphones quickly and easily depending on what I’m pairing with the unit.

The input button cycles through 5 modes: USB, Optical, Coax, Line, and Bluetooth.

We’ll get into all of that in a sec.

Rounding out the rest of the front panel is a power button, gain stage switch (High, Medium, Low), and the output switch (DAC, Preamp, Headphones).

FiiO K9 Pro Review

Let me just verify, that all the stuff I mentioned at the start is nice, but if you know me, you’ll know I don’t recommend DACS based on all that. I don’t even really recommend them based on sound either.

No, the reason I’m excited about the K9 Pro is due to factors totally separate from its technical specifications and any perceived improvement that results from them.

I love it because of its value and versatility. And you will too. Because you don’t really need anything else if you have one.

Before we get into its usage, let’s take a look at the back panel.

Back Panel

Firstly there’s the AC 110-115V~/220-230V~ power jack and the I/O switch on the left.

FiiO even provides a gigantic WARNING sign for users in different countries as using the wrong voltage input with your local nominal voltage may cause damage to the unit.

Select 115V if you are in the following countries:

USA, Japan, Canada, Mexico, Columbia, Guam, Jamaica, etc.

Select 230V if you are in China, South Korea, Russia, UK, Argentina, France, Germany, India, Malaysia, Singapore, Australia, etc.

The switch is located on the underside of the unit towards the back right.

To the right of the power switch and jack is the digital input section.

FiiO K9 Pro Review

Digital Inputs

Here we have Bluetooth, Coaxial, USB Type-B, and an Optical input. In the box is the supplied Bluetooth Antenna. Just screw it on and you’re all set.

To enter in, go into your phone’s settings and press Bluetooth. Now press “Search” and wait. It should show up as FiiO K9 Pro.

As mentioned in the introduction, one thing FiiO could improve on is the time it takes for the device to pair with your phone and/or the number of attempts taken.

Sometimes I’ll try 3-4 times before it accepts.

For instance, I don’t have any issues pairing iFi products with my phone, but I sometimes run into longer than desirable wait times with FiiO products.

I go into this a bit more in-depth in the Go Blu Review as well as the Best Portable Headphone Amplifier Guide.

To the right of the digital input section is the Analog section.

Analog Section

Here we have a 4.4mm line-in, RCA line inputs, RCA line outputs, and XLR balanced outputs.

Now let’s go over everything you can do and the options you have at your disposal.

FiiO K9 Pro Review

Digital Inputs

Bluetooth/Phone Option

As alluded to above, you can pair it with your phone if you have some speakers handy.

I just bought a set of Eris e3.5 speakers and this option works well if you have guests over as you won’t have to control the music from your laptop. Since the Eris’ are nearfield monitors and meant for mixing purposes, I’d probably invest in a different set if one of your main goals is to listen wirelessly.

Still, for around $230 (Zen Blue + Eris) you can have a simple Bluetooth setup in your living room without the need for a separate receiver and passive speakers. Related: How To Set Up A Home Theater System For Beginners.

The problem with that is you don’t get all the versatility of the K9 Pro.

K9 Pro vs. Zen Blue

I thought it would be interesting to compare the Bluetooth range on both and determine which is better.

Both do fine keeping a connection while I’m sitting on the couch about 10 ft. away (as they should), but what about connected to speakers?

The Zen Blue’s range is about 30 ft. before it starts cutting out. I tested this by walking outside of my apt. and leaving the door open.

I could get to the entrance of the breezeway and it was still playing music but cutting out intermittently. Inside, I can be anywhere in my apt. and it won’t cut out at all.

Do keep in mind the Zen Blue is pretty much a receiver only, so you’ll have to pair it with a separate amp if you want to listen with headphones. I was using the Gryphon. With speakers, just use the supplied RCA to RCA cables in the box.

By contrast, the K9 Pro’s range maxes out at around 22 ft. I can only walk about 3 feet outside before it starts cutting out.

This likely won’t matter much as both units do fantastic inside the apartment, but it’s something to keep in mind regardless.

FiiO K9 Pro Review

FiiO Control App

Another feature FiiO offers is the Control App, which was a bit persnickety to get up and running but works pretty well all things considered.

This isn’t what you’ll primarily be buying the K9 Pro for, obviously, but I suppose it’s a cool little add-on.

It is free, with features including an EQ profile and various filters, none of which I found particularly useful.

The EQ feature is okay if you use the supplied presets, but attempting to modify/customize the different frequencies yourself is almost an exercise in futility.

For instance, a simple 2dB bump for any frequency actually makes the headphones sound considerably worse and weirdly makes the volume lower, but this could just be a product of trying to EQ over Bluetooth – something you should probably avoid at the end of the day.

FiiO K9 Pro Review

FiiO K9 Pro ReviewFiiO K9 Pro Review


This is great for stuff like TV Sets, CD/DVD Players, etc. So anything that outputs Coaxial can be used with the K9 Pro and comes in handy when you don’t have HDMI as an option to transfer audio data.


My preferred method of transfer is optical, and fortunately, the K9 Pro has that as well.

So I can use it with my PS4 via Optical cable from the output on the back of the Playstation into the K9 Pro’s input.



This will be your primary connection to your laptop and comes in the form of a USB Type-B to Type-A cable, standard for most desktop units, FiiO or otherwise.


There’s also a Type-C slot on the right-hand side, and I’m assuming you can connect to your laptop or phone that way as well.

Analog Section

Perhaps the second most used feature will be your RCA outs which can connect to various types of gear as a preamp.

My Eris e3.5’s mentioned earlier come in handy here and you have a few options:

  • RCA to RCA. For this, just use the K9’s RCA outputs and connect the other ends to the e3.5’s inputs on the back.
  • RCA to line. Same as above, only you’ll plug the other end into the front of the e3.5 where it says “Aux-In”.
  • Line Out to a separate Headphone Amp. If you want, you can utilize the K9 Pro as just a DAC and connect it to a separate amp of your choosing. Just make sure the Amp either has RCA inputs, a line input, or balanced inputs.

FiiO K9 Pro Review

Line Inputs

Line in from separate DAC. The K9 Pro works as just an Amp from a separate DAC of your choosing. Utilize the RCA inputs or the 4.4mm line in.

For instance, you can connect an iFi Zen (via its 4.4mm output) with the K9 Pro via 4.4mm line cable into the K9’s input.

You can also use the K9 Pro with a turntable like the Audio Technica AT LP60. Just make sure to flick the switch on the back to “LINE” and connect the Male RCA cables from the Turntable into the Line input on the K9.

From here you have 2 options:

    1. Listen with headphones.
    2. Output the sound to your speakers. More on that in a bit.

XLR Balanced Output

Finally, we have what is perhaps the coolest feature on the back; balanced outputs for use with speakers that utilize balanced inputs.

Fortunately, the Eris e3.5 has us covered there as well. Just snag a set of XLR Female to 1/4-Inch TRS Males as I did and you’re golden.

But wait, there’s more.

Headphone Section

Here we have 3 different options:

  1. 4-pin balanced XLR
  2. 6.35mm (1/4″ single-ended)
  3. 4.4mm balanced

Are you starting to understand now, Mr. Krabs?

While we’re’ on the subject of headphones inputs, let’s discuss the K9 Pro’s sound.


FiiO K9 Pro Review

You may notice the Potentiometer seems to take a bit of turning to get the volume loud enough, but upon further research, this is due to its ADC Curve reconstruction. Let’s take a look at some more of FiiO’s literature:

Adjusting the volume may look like a simple concept, but a good execution of it is crucial to an excellent audio experience. The ADC curve reconstruction method of volume adjustment used in the K9 Pro effectively minimizes any left-right channel volume imbalance and noise. It also results in a smooth change of volume across all levels. This attention paid to the simple process of volume adjustment is just another layer to making sure you truly savor your music with the K9 Pro. FiiO

Normally I’d say this is marketing-speak, but in testing for myself at very low volumes I found there to be virtually no channel imbalance.

Raising the volume is also rather smooth and fluid vs. sudden and jarring which is something you’ll come to appreciate as well – especially when switching back and forth between various Impedance/Sensitivity ratings and headphones.

The K9 Pro ensures you’re pretty much never going to be at risk of blowing your eardrums out, but still, make sure to turn the volume back down as a precautionary measure when switching headphones/sources regardless.

A neat feature of the K9 is that it will gradually raise the volume when switching between sources or just resuming a listening session after pressing play.

This gives you time to quickly turn the volume down if you happened to goof and forgot to turn it down initially. The only other DAC I’ve tried that had this was the beloved Oppo HA-2.

Sound Profile

FiiO K9 Pro Review

The sound itself is typical AKM – smooth and velvety but still detailed. It’s not tube level warm, but it never feels overly clinical or sterile sounding.

I like to think of it as a cross between neutral and warm, and given it’s advertised less than 1 Ohm output impedance, this makes sense.

Music is simply enjoyable to listen to and make no mistake, this sounds like a premium product in every facet.

I’ll still always urge you to seek out good quality source files as they are of the utmost importance, but the K9 Pro certainly delivers in terms of providing a clean backdrop for your music.

I’d feel comfortable driving anything with the K9 Pro which is yet another reason in a long list of many to invest in one for the long haul.

To be sure, 278mW into 300 Ohm (as advertised) is plenty here and you won’t have an issue with any headphones you may have.

I’m also not sure if this number is peak power or continuous, so if you know, definitely comment down below as it’s a pretty important distinction that a lot of companies don’t bother to clarify.

Again, I’m more concerned with value and versatility, but the K9 Pro doesn’t disappoint on the sound front.

The Arya is a perfect headphone to use in evaluating the K9, as the headphones are neutral, open, and incredibly transparent/honest – so much so that they don’t always sound good and most certainly do not put lipstick on a pig.

If your source is even slightly mediocre, you’ll know immediately.

FiiO K9 Pro Review

K5 Pro Comparison

The Arya sounds smooth and clean through the K9 Pro, but what’s interesting to me is going back and forth between it and the K5 Pro.

You may assume that the K5 Pro would be warmer (given its slightly higher Output Impedance), but to my ears, this actually isn’t the case.

The K5 Pro sounds ever so slightly more brash and prickly for lack of a better word.

It’s subtle, but I think the K9 Pro slightly outperforms the K5 Pro in terms of a refined, lush sound. The K5 Pro doesn’t sound like a cheap unit in comparison, it’s just not quite on par with the K9 Pro’s improved overall sound profile.

I think the K9 opts for a smoother, slightly more velvety presentation, but it also seems to emphasize vocals and spacing a bit better.

Voices seem a bit more intimate, and the Soundstage generally feels more expansive. Take these impressions with a grain of salt, as they’re simply my own interpretations and I haven’t read anything about this unit.

I could be totally wrong, but I’ve been going back and forth for quite a while through the duration of the demo.

I’m sure at some point down the road some snob will come out with an article saying how the K9 Pro actually isn’t that good, and in advance, I’m telling you right now, I don’t give a flying crap.

Lol. So don’t @ me. 🙂 Thanks!

FiiO K9 Pro Review

In terms of sound alone, is the K9 Pro worth roughly $550 more than the K5 Pro?

In my opinion, absolutely not, but again, this isn’t why I’m recommending the K9 Pro over everything else (as mentioned previously).

If the K5 Pro was my previous do-all unit, the K9 Pro only improves on that notion by adding even more options at your disposal without going overboard on price.

Speaker Pairing

With the e3.5 it’s more of the same.

It may be my imagination, but I experienced a slight upgrade when switching over to balanced. It kind of feels like the music takes on a slightly liver flavor. Instruments and voices seem to be fleshed out a little more, with superior decay and realism.

Could a simple reduction/eradication of unwanted noise in the transfer be the culprit? Maybe, maybe not. I used balanced monitors for years (LSR305 + Scarlett 2i2) and loved them, but I don’t know if they make that much of a difference vs. an unbalanced connection.

For as much as people obsess over using balanced, I personally think the distinction is incredibly subtle if it’s even there at all.

Still, if I have the balanced option at my disposal you can bet your buns I’m probably going to use it over a single-ended connection, so take that for what it’s worth.

Gaming & Film

FiiO K9 Pro Review

So, you want to use the K9 Pro for gaming and film duties. Well, it’s got you covered, but I’ll be honest; As with the K5 Pro, this is not a unit you’ll want to be frequently moving around too much.

To test it out with my PS4, I had to remove 2 balanced cables, the RCA cables, the USB cable, and the power jack from the unit.

You then have to carry it to where your PS4 is and reconnect the USB, Power, and finally run an optical cable from the back of the console into the K9.

Make sure to switch the input to optical and flick the switch on the front to “HP” (Headphones).

In short, I’d plan to keep this unit in one spot. In other words, moving it around is not something I look forward to.

What I do love is how it sounds with gaming and film. I’m not going to sit here and yammer on and on about how it’s light years better than a G6 or K5 Pro because it’s not. Is it slightly better? Sure, and I mentioned that in the sound section.

For me, it’s simply another way out of the many you can utilize this unit to do basically whatever you want and that’s why it’s so valuable.

Vinyl Listening

  • Connection: Line
  • Album: John Coltrane – A Love Supreme (1964)

Speaking of doing whatever you want, you can even use the K9 Pro with a USB turntable as mentioned earlier.

Just connect the RCA males from the record player into the back of the K9’s Female inputs, and then Run RCA to RCA from the outputs of the K9 into the inputs of your speakers.

Again, I’m using the e3.5’s and AT LP60 from Audio Technica while spinning one of my all-time favorite Jazz Records; John Coltrane’s “A Love Supreme.”

Try it out!

If you want to listen with headphones, just plug some in and turn the volume down on your speakers.

K9 Pro AKM version vs. ESS version

I received the ESS version in the mail and have to say I prefer it a bit over the AKM version.

If you’re a regular reader or subscriber, this won’t surprise you much as I’ve swooned and drooled over the ESS sound for the better part of 4-5 years now dating back to 2017-2018.

So I’m not just blowing hot air here; I truly enjoy the crisper, brighter, more lively sound that it provides which is why I still recommend the DragonFly Red a lot.

Make sense?


Now, is the ESS sound for everyone? Absolutely not.

You may find it to have a bit too much glare (dubbed the Saber glare by snobs) and feel as if it’s too accentuated and overly zesty.

I totally get that (it’s still kind of nitpicky), but I’m just telling you that I personally. prefer it. That’s all. So again, don’t @ me.

One of the reasons why I like it better is because the music just feels more lively, more exciting. Voices tend to sound more present and immediate, and I feel hornier because of it.

I actually cried today listening to Smokey Robinson’s “More Love” through the Apos Caspian utilizing the K9’s balanced jack.

It was one of those experiences that makes you remember why you love music and yes, sometimes gear does come into play and helps considerably.

The combination revealed 99.9% of every single little minute detail that went into the recording, and I was astonished because I had never heard it in that way before. This is just one reason why Motown music is still played today. There’s truly nothing like it.

For as much as I get on people for over-exaggerating what are actually super subtle differences between DACS, the ESS sound is one example of something that will always stand out as being markedly different than a lot of other chips.

Aside from the sound, the physical stature of both are identical aside from one small efficiency change – FiiO put vents on the left side to help dissipate the heat that emanates from the DAC.

Final Word

FiiO K9 Pro Review

What more could you ever want in a DAC/Amp?

As mentioned at the start, the K9 Pro will pretty much be replacing every recommendation I have on this site with regard to desktop/best of Amps & DACS. I also don’t foresee it leaving the top spot any time soon.

I’ll probably still recommend the K5 Pro/ATOM for beginners who don’t want to spend a fortune right away, but even so, why not just go for the gusto and never upgrade ever again?

The K9 Pro is an astonishing cross-section of price to performance ratio and value vs. money spent. There are amps out there costing thousands of dollars that don’t do a fraction of what this thing is capable of.

Sure, their claim to fame may be “better sound” but you know better than that by now that those grand proclamations are rather hollow when you know the truth about Amps & DACS.

In my mind, $700 is a bargain considering everything we’ve discussed today.

In fact, it’s a steal.

K9 Pro vs. Neo

There’s really only one unit I’ve tried currently on the market that competes with the K9, and that is iFi’s Neo iDSD. I was excited about that one for obvious reasons (Value/Versatility), and both units are incredibly similar.

Both are priced similarly, both have XLR outputs, RCA Outputs, Coaxial In, Optical In, USB Type-B, and Bluetooth. Both also have 4.4mm and 6.35mm headphone connections on the front.

Both can be used with Tidal MQA, both support DSD and hi-res files although the Neo can play up to 768kHz and DSD512 while the K9 is only capable of 384 and 256.

For me, that doesn’t really matter much, but your mileage may vary.

I also don’t run Tidal anymore for a few reasons, but that’s neither here nor there.

The K9 Pro adds RCA inputs and a balanced XLR connection for your headphones. It’s also heftier and seems built better than the Neo.

I can’t comment directly on sound at the moment as I don’t have the Neo here anymore.

It’s obvious FiiO’s looking to compete with iFi in this particular segment of the DAC market, and I think they have a better overall product and a slight edge here at the end of the day.

Interested in the K9 Pro?



Well, that’s about it for today my friend! I hope you’ve enjoyed this FiiO K9 Pro ESS and AKM Review.

Questions? Comments? Requests? Did I miss the mark on something? Please let me know down below or Contact me!!

If you love what I do here and want to support the blog and channel in a more personal way, check me out on Patreon and discover all the value I have to offer you.

Is the K9 Pro worth a purchase? I would love to hear from you. Until next time…

All the best and God bless,





Can’t decide which headphones to purchase? Interested in a complete buyers guide outlining over 40 of the best options on the market? Click on over to the best audiophile headphones to learn more!!

Photo Gallery


Apollo Brown, Stalley – Blacklight (2021)

Big K.R.I.T. – 4eva Is A Mighty Long Time (2017)

Gleemer – Down Through (2020)

The Roots – Illadelph Halflife (1996)

John Coltrane – A Love Supreme (1964)

Khrysis – Khrysis On The Boards (2015)

Oh Wonder – 22 Break (2021)

Arrival (2016)

Jacob’s Ladder (1990)

What’s Eating Gilbert Grape (1993)

Se7en (1995)

War of the Worlds (1953)

The Machinist (2004)

Black Swan (2010)

The Outer Worlds (2019)

Don't forget to share if you found it helpful!

You may also like


Joel February 2, 2022 - 6:58 am

Can you add a comparison with popular stacks like smsl su9/su8 or topping a90/d90 E50/L50 or some other in the same price range?

Stuart Charles Black February 2, 2022 - 7:08 pm

Hey man! Yeah, I will definitely keep it in mind for the future! Would make for a nice shootout. Thanks for stopping by!

Dorian February 7, 2022 - 5:49 pm

Did bought fiio k9.
It is very good dac/amp
Sound stage is wide and 3D
Female Voices sound marvelous.
It is not hi-fi dac/amp
Just Play track 6 “Presto” Four Seasons Vivaldi.
Then go to the Filharmony and listen the same ” track ” in real.
K9 pro just makes that Violin attack soft and delicate.
It doesn’t sound right


Stuart Charles Black February 11, 2022 - 3:34 pm

Ok man, if you say so 🙂

Jenna Chaplin February 23, 2022 - 11:18 pm

I just got the K9, and your review was very influential in my decision. I pleased to say that I loved it immediately; the sound is very clear and natural which is just what I was looking for – even over BT with my iPhone 12. I’m just using it as a DAC into my amplifier (a perhaps outdated Arcam AV350) but it’s noticeably better than anything else I’ve tried. Thank you.

Stuart Charles Black February 24, 2022 - 5:13 pm

Thank you for the vote of confidence Jenna and you’re welcome! I’m so glad you’re enjoying it. I think you’ll love the features and all it has to offer. A truly great value!

Jenna Chaplin March 5, 2022 - 12:57 pm

Hi Stuart,
Very unfortunately, because I like the sound of this DAC, it looks like I’m going to return it because after using it for 10 days at approx 1 hour per day I suddenly started experiencing ‘drop-outs’ (about 1 second of total silence) in the middle of a track. It happened yesterday at least 3 times during the first movement of Rach 3 and then again today during Lief Ove Andnes’s Mozart 20. Before I commit to returning it, I’m wondering if you’ve any suggestions or if there is a solution out there? I connected it to my Mac and it showed that I do have the latest firmware 1.13.

Stuart Charles Black March 6, 2022 - 2:49 pm

Hey Jenna!

I would reach out to FiiO and get a replacement unit as you may have gotten a lemon or perhaps it just needs a driver/firmware update. That seems to fix all of the issues I’ve had with their products.

Jenna Chaplin March 5, 2022 - 1:09 pm

…and I meant to add that this first happened with a wired optical connection and then later it also happened over bluetooth – which I would not be too suprised at, but would, at this price (CAD$1250 inc tax), find unacceptable.

Stuart Charles Black March 6, 2022 - 2:50 pm

Yeah, it could just be driver/firmware. I’ve had some strange issues with some of their stuff and that’s always fixed it immediately. In fact, I was having an issue with the K9 and my speakers (buzzing/static, etc.) and an update did the trick.

Jenna Chaplin March 5, 2022 - 1:27 pm

Sorry, it’s me again. I tried to subscribe but every time I try to confirm and do the Captcha I get this

“We couldn’t process your request at this time. Please try again later. If you are seeing this message repeatedly, please contact Support with the following information:”

Stuart Charles Black March 6, 2022 - 2:50 pm

Hey! What did you try to subscribe to?

Jenna Chaplin March 6, 2022 - 4:59 pm

Hi Stuart, thanks for your helpful replies. I actually decided to exchange it at the store for the Cambridge Audio CXA81 (quite a bit of extra $) as I had been thinking of doing that originally (replacing my old Arcam AV350 which I liked) but then I found the K9 and really wanted to try it. I guess I was just unlucky with my unit as I wanted to hold on to my Arcam. I would have liked the DacMagic 200M but they are nowhere to be found other than by wating for 2 – 3 months.
To subscribe to your ‘in-depth content’ I just used the link at the bottom right of this page – directly right of where I’m typing. I got the email asking me confirm, clicked on the link. I’d still like to do that when the link works.

Stuart Charles Black March 7, 2022 - 9:45 pm

Thank you for bringing that to my attention. Seems the form is not working. I will fix it and let you know.

Sorry to hear it didn’t work out with the K9 but keep me posted on your impressions of the CXA81. I really do enjoy Cambridge products (the ones I’ve had experience with).

Stuart Charles Black March 7, 2022 - 10:30 pm


I just fixed it, did a test subscription with one of my emails and it worked. Can you clear your cookies/cache on your browser, try again and let me know if it goes through? Should say “Thank you, your sign-up request was successful! Please check your email inbox to confirm.” Also you can try other browsers as well. If it does go through, check your spam folder if you don’t see it in the main one. Thank you! 🙂

Jenna Chaplin March 14, 2022 - 6:47 pm

Website won’t let me post; keeps displaying same screen

Stuart Charles Black March 14, 2022 - 7:14 pm

Hey not sure what that’s about but the comments go through just fine. No worries. Yours came up 5 times lol. I generally just delete the duplicates as I get them quite frequently. It’s not a big deal on my end but I’m sure it’s confusing on yours. I don’t know what causes this.

Jenna Chaplin March 14, 2022 - 6:49 pm

Is there a size limit? I have a full reply of the info from the failed attempt to subscribe.

Stuart Charles Black March 14, 2022 - 7:14 pm

Nah there isn’t. Just replying to this so you know it went through.

Jenna Chaplin March 14, 2022 - 6:49 pm

Strange indeed – Trying again..

Hi Stuart,

Everything appear to work until the very last step after I prove that I’m not human and then click subscribe. Then I get a screen ( https://homestudiobasics.us19.list-manage.com/subscribe/confirm ) like this (I’m not able to paste an image here so I just copied the text – see below. I am running Adblocker and Privacy Badger but I turned them off for this site (as otherwise I can’t post here anyway).

Server Status

We couldn’t process your request at this time. Please try again later. If you are seeing this message repeatedly, please contact Support with the following information:


date: Mon Mar 14 2022 14:34:54 GMT-0400 (Eastern Daylight Saving Time)

url: https://homestudiobasics.us19.list-manage.com/subscribe/confirm

user agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:98.0) Gecko/20100101 Firefox/98.0

Please let me know if there is a fix for this. It’s too much trouble to keep on doing the Captcha every time before it fails.
The CXA81 just arrived this morning. It does have the more ‘forward’ character as described which contrasts with the more neutral sound of the FiiO. I’m not sure yet if I prefer it but it certainly is very good. More later perhaps. Thanks.

Stuart Charles Black March 14, 2022 - 7:15 pm

Weird. I can just manually subscribe you if that’s cool with you. Let me know 🙂

Jenna Chaplin March 14, 2022 - 6:50 pm

Seems that there is, so I can’t paste in all the diagnostic info. Oh well.

Stuart Charles Black March 14, 2022 - 7:17 pm

Ah. Thanks for trying. Gonna have to figure out what’s going on.

Jenna Chaplin March 14, 2022 - 10:39 pm

Sure, please manually subscribe me if that’s easier. Thank you.

Stuart Charles Black March 15, 2022 - 2:11 pm

Will do Jenna! 🙂

Jenna Chaplin March 16, 2022 - 8:42 pm

A quick note on the Cambridge CXA81 now that I’ve had a few days to listen to it. At first I thought it sounded a bit too ‘bright’ (we have no choice but to be subjective here but I guess you know enough to imagine what I’m describing) but now I think of it as perhaps more ‘lively’ than the FiiO. In retrospect I do feel that the FiiO was just a little too ‘smooth’ – even though I liked it a lot. The impression of the FiiO was more like that of listening to a good hi-fi system rather than listening to a ‘performance’ which is my experience of listening to the CXA81 – so now I do feel happy with my choice.

Stuart Charles Black March 16, 2022 - 9:24 pm


Interesting observations! I just had a look at the output impedance of the CXA81 and it’s a minuscule 0.1 or thereabouts so your “bright” impressions line right up.

I personally really enjoy the super neutral variety but headphone pairings can be tricky for obvious reasons.

Jenna Chaplin March 16, 2022 - 8:42 pm

Hmm, that last comment isn’t showing but I’ll not repeat it as I’m guessing you can see it but I can’t.

Stuart Charles Black March 16, 2022 - 9:25 pm

Yeah, I have to approve them first so after commenting I’d generally give it anywhere from a few hours to a day depending on if I’m in the office or not.

Jenna Chaplin March 17, 2022 - 4:51 pm

Thanks Stuart. I have the B&W P9’s which I’m very happy with. I’ve just always only had B&W speakers so stuck with them for my headphone choice. Thanks to your articles on audiophiles and marketing I’ve now let go of the (always unnecessary!) embarrassment I used to feel for still owning my 40-year old B&W DM7 Mk2’s. I know the bass extension is perhaps their weak point but the way I have them set up in my room seems to take care of that well enough. I also have the Audioquest Dragonfly Cobalt (yes, I know… could have gone with the Red but was persuaded by reviews!) and like that too.

Stuart Charles Black March 19, 2022 - 3:04 pm


My Dad still has his B&W speakers from the ’90s and they sound incredible – always have. I actually really enjoyed the P9 though it gets some hate around the internet and I don’t really know why. The P7 sounded God awful but the P9 was definitely better.

You will be interested to know that Apos reached out about the new ESS version of the K9 Pro which they are sending over for demo. It uses the Sabre chip (vs. the AKM in this article) so will be much more in line with your preferences. I will keep you posted.

Jenna Chaplin March 19, 2022 - 5:50 pm

Thank you, Stuart, I’d still be interested in a K9 Pro – as a headphone amp plugged into my bedroom where I do my headphone listening. Look forward to hearing more.

Stuart Charles Black March 21, 2022 - 4:10 pm

Welcome! 🙂

sonu March 29, 2022 - 3:04 pm

Today I was searching some blogs on Google and when I went to someone’s site and saw and read their blogs, I did not like anything and when I came to your site and saw your site, I liked your site very much.

Stuart Charles Black March 29, 2022 - 7:28 pm

Thank you, Sonu!


Leave a Comment