It will depend on the equipment. I guess every combination of amp and source will have it's sweet spot. Just a matter of trying what works best.

I believe some digital sources only have volume control by attenuating the digital signal (by reducing bit depth thus dynamic range). If this is the case having the source at 100% will have an advantage as long as the amp in the source can put up the volume cleanly and the amp can handle the input.

I started a thread about this in the "sound sience" sub forun but no replies to date.

When I run my android tablet through my bravo tube headphone amp it is clear that the combination works best with the source at about 60% even though I suspect the volume control to be in the digital realm (pre-dac).

Quote:

Originally Posted by HiFlight 

Although this topic could be argued pro and con endlessly, I have always run the source near max for best s/n ratio as well as for maximum dynamic range.   Below is an excerpt from a professional sound recording site that may be of value in understanding the rationale for a high source level.   Although we are considering a headphone amplifier, for all practical purposes, it can be considered the equivalent of a mixer.

 

Quote:

 

Maximising the dynamic range

All equipment has dynamic range. This is the range between the quietest and loudest signals it can accommodate, or between the noise floor (beneath which a sound cannot be heard) and distortion. A signal entering a mixer needs to be as loud as possible without overloading the circuitry and causing distortion.

Setting the best signal to noise ratio

All circuits produce a fixed level of noise (hiss). If the source signal is loud enough this noise will be less noticeable.

HiFlight, I think we are confusing what source signal is to the output or volume of the source component and in this case it is the computer that is what we are talking about in this thread.  Of course, when it comes to signal to noise ratio, the higher the better as in above 100.  And it is always desirable if there is sufficient amplitude and S/R ratio in the recording signal.  But when the computer start increasing volume output to the external portable amp, the portable amp is only amping the amp signal from the computer.  This is the same reason why we use LOD and not headphone out of the ipod when we connect to an external amp because we do not want to amping the amp signal from the headphone out.  In your quote, they are talking about the incoming recording signal.   

Quote:

Originally Posted by Jalo 

HiFlight, I think we are confusing what source signal is to the output or volume of the source component and in this case it is the computer that is what we are talking about in this thread.  Of course, when it comes to signal to noise ratio, the higher the better as in above 100.  And it is always desirable if there is sufficient amplitude and S/R ratio in the recording signal.  But when the computer start increasing volume output to the external portable amp, the portable amp is only amping the amp signal from the computer.  This is the same reason why we use LOD and not headphone out of the ipod when we connect to an external amp because we do not want to amping the amp signal from the headphone out.  In your quote, they are talking about the incoming recording signal.   

 

Good point!  I rarely, if ever, re-amp an analog headphone output from a soundcard, DAP or anything else.   All my players have a line-out which I use.  Some have a volume control for the line-out, but I still run these at about 100% into my amps.  The ones that have a fixed line-out such as my DAC's I take what they provide. 

I have never tried the headphone output from my computer, as I am assuming that it isn't worth the trouble.  I use either optical out or USB, with the preference going to optical. 

I really am considering my source as a pre-amp. 
 

I'm using the laptop feeding a DAC/amp combo, so IME:

digital player on pc at max vol,

then set the (analog) volume control of dac-amp to my level need.

YMMV, of course.