Fiio K9 Pro ESS + Audeze LCD-2C strange distortion

[piku235]

Hi all,

My equipment:

• Fiio K9 Pro ESS
• Audeze LCD-2C & Sennheiser HD650
• Listening on Apple Music (loseless)

While playing around with different GAINs I encountered strange distortion on L and M that were noticable on volume knob at 3 o'clock (75%) and greater. After switching GAIN to H, the distortion almost disappeared, it was only barely noticeable. I've tried many things, USB and BT inputs, I've also tried it on Windows PC, everywhere the same effect, both on LCD-2C and HD650. The distortion becomes even worse when the EQ is enabled via Fiio Control App with boosted 31.5Hz and 63Hz at 4dB+. It got a little better when I used the balanced output with my LCD-2C.

I know that maybe this is just how this DAC behaves, but what bugs me I still have my old Creative SoundBlaster X7 that uses TPA6120A2 and I have no distortion, regardless of the volume level. I also set it to high gain as Fiio, but they remained clean. I especially liked its EQ where I could set both 31.5Hz and 63Hz at 7dB+ drawing more bass from the LCD-2C without any sign of distortion. Unfortunately, this is where K9 Pro let me down, although they play clearer and brigther than X7.

Do you have any idea why this happens? Is it maybe my misunderstanding of something?
Thanks in advance for your answers!

 

[piku235]

Ok, after deeper testing I've managed to narrow down the issue. Unfortunately, it seems that my K9 Pro ESS is defective, specifically the left channel of the headphone output (both XLR and 6.3). I spent some time testing, and at some point it occurred to me that only left channel seems distorted, the right channel was completely fine. I started testing again having only one of the headphone channels connected. I tested on both LCD-2C and HD650 and the result was the same. Only the left channel had distortion, and they were quite noticeable, even when I wasn't wearing the headphones. I plugged the cable from the left channel to the right channel of the headphones and distortion was also there. With the plugged cable from right channel to left and right channels of headphones separately, no distortion.