[jlch]

I mean : as far as sound quality and/or battery life are concerned.
If there are no differences, why not always stay switched to "high gain" ?

 

[chocky900]

I've been wondering this lately. Also if it is better to use a low gain mode sometimes how can you tell when?

 

[bellor]

The Low and High gain settings are simply 6dB apart. 6dB means 2 times amplification. However, this also means 2 times amplification of noise. The difference is not so much, so the noise floor will not be very noticeable unless you are very fussy. However, 2 times the voltage means you can drive harder to drive headphones.
There is, theoretically, no reason to not keep the player on low gain and raise the volume as needed, as long as the maximum volume is sufficient. If the volume is not enough, then high gain can solve the problem.
However, using high gain with low volumes does 2 bad things: amplifies the inherent noise floor and also exposes the output signal to corruption of silence bits or soft sounds, since the dynamic range is less than normal for the respective noise floor (which does not change with volume settings, since it is not an input signal, but a characteristic of the output stage of the amplifiers).

 

[dudiadudia1]

didnt understand so high or low?

 

[HK_sends]

  didnt understand so high or low?

High gain/low volume is noisier with sensitive headphones.  Low gain is usually quieter but needs more volume to get to the same sound level as high gain.
Look at the impedance rating of the headphones.  Typically...but not always...the higher the ohm number, the harder to drive the headphones.
IIRC, gain also adds power to the output so high gain will probably shorten your battery life.
 
All that said, whichever sounds better to you should be just fine.
 
Disclaimer:  All the above is IMHO and YMMV.  Hope this helps.
Cheers!

-HK sends

 

[chriswangux]

My understanding is that the Hi/Low Gain toggle is designed for what type of audio source you are using.  Either battery driven or AC power driven. 
If you are using portable player driven by batteries, use the Hi gain since the output from audio source is relatively low. 
If you are using device that has higher output, like desktop, laptop or maybe you playing from guitar, use Low gain since the ouput from source is pretty high. 
 
I couldn't find any explanation from Fiio about the toggle, but there's one from Bose about a similar switch on their headphones
http://worldwide.bose.com/productsupport/en_us/web/article_265_using_the_hi_lo_switch/page.html?productlabel=qc15
 
And I find this tip from Bose pretty useful.  
 
"If the HI/LO switch is set to LO and you have to increase the volume control on the audio source above the halfway point, remove the headphones. Change the switch to the HI position. Turn the volume control on the source down low. Put the headphones on and slowly increase the volume on the source."
 
That's for the switch on their headphones though, so I'm sure 100% sure if it applies to music players or amps. 

 

[dudiadudia1]

i feel the high gain affects the bass response..
in that sense it does have an effect on the sound.