[ndburley]

  it was not meant at you but at Inszy because I have not seen him posting any user impressions so far.
 
here are some pics of the sensitivity of the volume knob with my heir 8:
 
"zero" volume after the starting hump
http://s15.postimg.org/lgcp1p7ej/vol_state_0.jpg
 
bit loud but listenable:
http://s24.postimg.org/8wb85ukkl/vol_state_1.jpg
 
very loud, feels unpleasant after short while:
http://s23.postimg.org/3p88n5pej/vol_state_2.jpg
 
you probably wont notice any difference between 2nd and 3rd pic. any more than the third pic and its very unpleasant. also I can hear (only faintly but its clearly there) song playing even when in 0 volume (but only in Coax mode, not when using Android phone).

Optical cable came today so thought I would have a test session with the volume. This I know is not the same set up as it is fed by my Sound Blaster X-Fi Pro and that is its blue light behind.
Firstly I tested my Sound Magic E10 at 16ohm and yes I can see the volume increase quickly and a gentle hand would be needed to avoid cranking it up too quickly.
Next was my AudioTechnica M50x at 38ohm, this was more controllable with less of a sharp increase in volume and sat ok between 10 and 11 position while the SM was between the 9 and 10 ish. 
Finally my BeyerDynamic DT990 Pro 250ohm which cranks up smoothly with less of an increase and can sit not too loud between 12 and 2 o'clock positions. 
 
My conclusion is that yes lower ohm earphones you need to be careful with as the optical feed is sensitive on the volume control but not uncontrollable and if someone has some 600ohm cans to test. The volume for me is not just a sudden jump but a little rotation means a lot. This is how I would imagine it to sound like using USB with gain set to full. 
Although this is not a deal breaker for me if some people are using really sensitive IEMs you will need to be careful of the volume increase. 
Hope that helps a bit

 

[RedTwilight]

Hmm I see.. Seeing that the minimum gain is +6dB gave me pause. If they could have a -3dB or even 0 that'd be great.

 

[SDBiotek]

For what it's worth, I received my XD-05 recently,and it works just fine with my Noble iems when I use the optical out from my AK100 II. I'm not running into any issues with being able to set the volume at a reasonable level. I wonder if haens' unit has a bad volume pot.

 

[RedTwilight]

  For what it's worth, I received my XD-05 recently,and it works just fine with my Noble iems when I use the optical out from my AK100 II. I'm not running into any issues with being able to set the volume at a reasonable level. I wonder if haens' unit has a bad volume pot.

 
How do you find the sound?

 

[SDBiotek]

I haven't had much time to use it yet and get a good handle on how it sounds. So far, though, I like it. Detail retrieval is very good, and overall it seems neutral in character. The bass boost works very well as noted above. I'll add some more impressions soon.

 

[RedTwilight]

I haven't had much time to use it yet and get a good handle on how it sounds. So far, though, I like it. Detail retrieval is very good, and overall it seems neutral in character. The bass boost works very well as noted above. I'll add some more impressions soon.

 
Alright, thanks! Keen to find out your view as well. Thinking of using it as a prospective upgrade/ sound tweak to the Fiio X3C. 

 

[mayi]

Have you tried contacting them? They must be able to help you, the tech support.

 

[Inszy]

  Hmm I see.. Seeing that the minimum gain is +6dB gave me pause.

Minimum gain is +3dB. Next is +6 and +15.

 

[RedTwilight]

  Minimum gain is +3dB. Next is +6 and +15.

 
Ah you're right! That's not too bad then.

 

[Aradea]

I haven't had much time to use it yet and get a good handle on how it sounds. So far, though, I like it. Detail retrieval is very good, and overall it seems neutral in character. The bass boost works very well as noted above. I'll add some more impressions soon.

Hopefully there will be comparisons with other amp+DAC as well

 

[RedTwilight]

  Minimum gain is +3dB. Next is +6 and +15.

 

   
Ah you're right! That's not too bad then.

 
Was looking at it on Aliexpress and then saw that the minimum gain is +6. Went to the main site to verify too and seems like it's +6? Making the gains +6/+9/+15.
Is the description on the first page correct? http://www.xduoo.com/xduoo/EnProductShow.asp?id=63

 

[Inszy]

Maybe they change that? It was +3/+6/+15.
 
Battery: 3.7V/4000mAh rechargeable lithium polymer battery within
Display: 0.91 inch OLED screen
System: Win7, Vista, XP Win8, Mac, OS X Win, IOS, Android system
Output power: 500mW (32Ωload)
Frequency response: AMP:10Hz~100KHz (±0.5dB)
                    USB/SPDIF: 20Hz~20KHz (±0.5dB)
Sampling rate support: USB
PCM:16-32BIT/44.1-384KHZ
DSD: DOP/NATIVE mode, DSD64-256 (1bit/2.8M-11.2M)
DXD:BIT/352.8-384KHZ 24-32
OPT/COA
PCM:16-24BIT/44.1-192KHZ
Gain: +3/+6/+15dB
Bass boost: 0/+6dB
Distortion: 0.0025% (1KHz)
Noise-Signal: 112dB
Adaptation Headset impedance: 8Ω ~ 300Ω.
Battery life: >11H (USB IN), >16H (SPDIF IN), >23H (AUX IN)
Charging time: Quick charge 5H (with charger), slow charge 11H (with computer)
Size: 139.5*75*23mm
Weight: 270g

 

[RedTwilight]

Hm yea.. Hopefully someone can help clarify that. Any Xduoo rep here by any chance?

 

[leobigfield]

C'mon XDuoo, having 3 settings why no IEM friendly gain?

 

[Inszy]

Low gain is IEM friendly.