Fiio K5Pro Review and Measurements

Another impression: https://www.superbestaudiofriends.org/index.php?threads/review-fiio-k5.1605/

Don't worry, I'll get to the good stuff this weekend (the Amps and Sound Ovation). For now, we get this piece of entertainment. The K5Pro was of interest because a member mentioned that while it's not great in technicalities, the headstage is good. Good is that it's inside one's head, or that the plane isn't at one's ears. I can confirm this. The headstage is the best thing about the Fiio K5Pro. It's open and spacious. Actually almost as open as spacious as one of those EC DHT amps with the high-frequency AC filament heaters.



Unfortunately, that's where the fun stops. The amplifier in the K5 isn't incompetent. However, it's a bit below average (in all other respects except headstage) considering what is out there today. The highs are bit glarey and sometimes a bit sharp. The lows are murky. I don't know what's in the K5, but the presentation is slightly insipid. Think of it as a Magnius sort of presentation, same murky bass, glarey highs, but leaner and less warm. Or think of it as a Topping L30, but brighter and more difficult in the highs, less overly forgiving. Wait, think of the K5Pro as being similar to those default headouts from the RME ADI Pro. Yup, that's it: meh. Something's gotta give if you want expansive headstage for cheap.

I do think the K5 is bit less insipid than any of the aforementioned units. That's a good thing; but it's not by much. The K5 did seem to be less lean and glarey after being left on for an hour. All these impressions were arrived at via forced listening throughout one day before I took any measurements. It's best to listen and take notes before measuring stuff because... confirmation bias. Duh.

BTW, I used a Modi Multibit (tweaked for less organic tone and better clarity) as the source. So no, the lean tonality and slightly difficult highs were not from my source.

I now present the GONAD dashboard for the Fiio K5. This is amp only using the line outs. I am not using the internal DAC.

 

Standard stuff here to supplement the GONAD dash above. Feel free to ask for more.

Fiio K5Pro
0dBu into 300-ohms 1kHz


Some AC mains noise, but -105db down. It's fine. Harmonics are way down too. A bit more odd order (3rd and 5th) than the major even orders.

Fiio K5Pro
0dBu into 300-ohms 37kHz (to confirm GONAD result for 37Hz)


K5 no like to amplify 37Hz at a very reasonable voltage level. Lots of harmonics. This would be good result for a tube amp, but iffy for a solid-state amp such as this.

 

Now here is something concerning. I don't know what's going on here. Does the K5Pro suffer from NWAVGUY Objective 2 amp syndrome where it no like hot inputs? I have no idea because I do not know the topology of the K5. The kicker is that 2Vrms from a DAC isn't hot at all. It's normal.

0dBu into 300-ohms 1kHz
Output of APx555 set to 0.775Vrms, volume knob of K5Pro maxed*
*This is normally how we measure for workflow speed


0dBu into 300-ohms 1kHz
Output of APx555 set to 2Vrms (to simulate DAC output), volume knob turned down to arrive at 0dBU
*This is normally how people actually use amps.


Still, distortion levels are reasonable (remember dummies, we are getting down past -90db) although it's a bit scary because from the distortion pattern, it looks like we are seeing the onset of clipping.

 

Here is the potentiometer tracking measurement - keeping in mind the random nature of this, which can be very easily gamed by manufacturers who send cherry-picked samples to their favorite measurebator reviewer. The X-axis is attenuation (L). The Y-axis is the R-L channel difference.

Fiio K5Pro
Potentiometer Tracking


How cow! What sorcery is this? No wonder I was able to use my efficient Grados so easily! FWIW, the large diameter volume knob is wonderful. I like big knobs.

Turns out the K5Pro uses an NJW1195 as the volume control on a chip. I would be curious to see if this is responsible for the higher distortion at the 2Vrms input. I would also be curious if this would contribute to the spaciousness of the headstage. It is part with active components - and that will change the sound.

 

See gray box in top left of GONAD dashboard.

 

The K5Pro uses a cheap external switcher brick for the power supply. I'm not a fan of switching power supplies. There is a reason why we don't see them regularly with HiFi gear: they usually sound like shit. However, there are always exceptions. Linn has made some gear that used switchers. I owned Linn amps and preamps that used switches. The low-end Schiit and MOTU digital gear use switcher, and they sound pretty good.

That being said, the K5Pro does have this glare and weaksauce kind of sound that I normally associate with switchers. For those curious, and for future comparisons, here is a measurement to 1MHz.

Fiio K5Pro
1kHz 1Vrms into 100k-ohms
>1MHz bandwidth


There is a little spike around 750kHz. That's probably the switching frequency. Otherwise stuff looks pretty clean.

 

This one is distortion over the frequency range at three different output levels into 300-ohms.

 

Last few measurements using the internal DAC.

0dbFS level. Volume knob dialed down to get 747mVrms (closest I could get to 0.775) into 300-ohm load (Sennheiser HD6x** nominal). 1kHz and 37Hz.



0dbFS level. Volume dialed down to get 252mVrms (closest I could get to 0.245) into 30-ohm load (typical ortho load).
1kHz and 37Hz.



Using the internal DAC, we don't see the AC hum and harmonics. The AC noise was 110db down so not harmful. (Also AC hum and its harmonics generally don't sound like shit. It could be that we are used to it. Walk around in a house and especially a place of business with a microphone and RTA, and we will see it at much higher levels.)

The internal DAC performs well enough. However, I don't like seeing those hashy spurs from 5kHz on, specially those that don't harmonics of the signal and stay there regardless of signal. I've seen this happen with DACs that use cheap switchers. Yes, I do feel this affects sound. The mitigating factor is that the TPA6120 headphone amp chip used the the K5pro has a tendency to homogenize anything going through it so that source often doesn't matter much.

I will put this on a loaner. I mean, the headstage is more expansive than most other headphone amps. That itself places the K5 into an interesting niche. However, if there is no interest, this can go to @atomicbob for science experiments or @LetMeBeFrank for other experiments.