Fiio JM21 DAP USB DAC Performance

[ShinMolina]

I just received my Fiio JM21 this week, and I'm quite pleased with it. This is my first DAP running Android and I didn't know if I would like the experience or not. It works very well, the device is responsive and has enough output power to drive everything I have from Truthear Hexa to HD600 and Fostex T50RP Mk3. The device seemed to shut down once without pressing anything while playing music. This has only happened once a couple of days ago. Apart from that, everything seems to work properly.

As I saw in Fiio's website, the performance of the JM21 seems decent, achieving about 0.001-0.002% or 94-100dB THD+N. I hooked the JM21 to my Topping E2X2 Pro, which has some decent ADC, performance and looked at the spectrum of a pure 1kHz tone played from the DAP.

When the JM21 is working as a standalone DAP, the noise and distortion look pretty low, corroborating the specifications given by Fiio. But when you use the JM21 as a DAC or even connect a USB cable to the unit, the performance decreases significantly as the noise floor increases.

I currently don't have any USB isolator or anything like that to remove any possible ground loops that could affect the performance I'm measuring, since the standalone performance looks great. Would like your opinion on this matter or if I could do anything to get a more accurate result.

 

[ShinMolina]

Here are some pictures I forgot to add about the setup I used for the measurements.

 

[ppunter2015]

I think it looks very nice. I am looking for a new DAP as the battery of my shanling m6 pro is dying out. Thinking about this one for my next buy.

 

[monkeyboy]

I'm curious about this unit as well...I'm currently using an LG phone, but the battery is going and it's 50:50 that you break it changing the battery...I'm thinking about a Pixel with GrapheneOS, but you'd need a dongle, which I think would end up destroying the USB port...and I don't use any of the phone functions. But it seems like none of the DAPs are a performant as a phone dongle combination....

 

[ShinMolina]

This one doesn't compete in performance with the best dongles out there, but it measures well enough at a first glance and I can't find any differences in sound quality when compared to my E1DA 9038S G3 dongle.

I'm pretty happy with it. It has some minor bugs and in the latest firmware update the next and previous track physical buttons don't function as they should. But Fiio seems to be resolving the bugs and has done so for other previous devices.