# Dumb Question: Line Level / Line Out vs. Headphone Out



## Roen

I have a DAC / Amp that has an optional line-out mode.

Can someone explain to me the difference between headphone out in low gain, medium gain, high gain and line out?


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## MindsMirror

Line out is meant to be connected to an external amp. It does not have an amp built into the line out, and it is not intended to drive headphones. You may not be able to control the volume from the line out, as that job typically goes to the amp. The headphone out does have an amp so you should be able to control volume from it. It should be able to deliver more power to a headphone with less distortion.

Gain is very similar to the volume control. You will usually want to set the lowest gain necessary which will minimize noise. If it's not loud enough with full volume on low gain, then bump it up to the next gain setting.


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## ProtegeManiac

Roen said:


> I have a DAC / Amp that has an optional line-out mode.
> 
> Can someone explain to me the difference between headphone out in low gain, medium gain, high gain and line out?



Line Output
*Digital Receiver >> DAC chip >> Analogue Output stage >*_> Preamp stage >> Amplifier stage*_

Headphone output 
*Digital Receiver >> DAC chip >> Analogue Output stage >> Preamp stage >> Amplifier stage**

Gain setting determines how quickly it piles on power into the headphone/speaker. If you play GranTurismo, Forza, etc, you can go into the transmission settings panel and look at the virtualizer there. High gain is like having tall gearing for those short circuits with successive short corners, low gain is like the gearing used for circuits with long corners and sweepers, and then there's something in between in case you're at Suzuka for example. The way the car accelerates is like how loud the system gets as you move the volume knob.

_

*Sections in bold are on your DAC, italicized are on the separate amplifier._


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## Roen

Is it strange that my line out applies more voltage than my low and medium gain settings?


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## castleofargh

no it isn't particularly strange. a line out tends to follow standards so that he amp manufacturers can design their products knowing what signal they'll be fed. for desktop systems a line out should be about 2 or 3V, with an impedance somewhere around a hundred ohm. and same for line out designs, they expect to be linked to an amplifier input of several thousand ohm. so being plugged into a 50ohm headphone might be problematic for the line out as it was never built to provide much current. 

in the end each output has a specific use and the nominal results will be obtained by following the intended purpose.

as for gain settings, some amps are made to drive very low sensitivity headphones, some are built to drive portable gears. the high gain of one amp could be the low gain of another. each gain setting has a gain value, usually a multiplier value. it means that it will take the voltage the line out is offering, and multiply it by that gain value(if it can). so if the line out is 2 volt and the gain is 3X, the amp maxed out should reach 6V. that's what the gain value tells you. 
sometimes you get the gain value expressed in db instead but it's the same thing. +6db means doubling of the voltage that comes from the line out. 
aside from specific situations, I agree with the advice to use the lowest gain setting needed to listen to music loud enough. most of the time the difference will be minimal, but sometimes the higher gain values might clip the signal, or simply have more noise or a higher impedance output that may or may not sit well with the headphone you use. I personally always go for the lowest gain setting, and if the amp can't push my headphone loud enough, then I increase the gain.


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## Roen

Is it common to find that bass response / impact is stronger on higher gain vs. lower gain for similar, volume matched levels?


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## Makiah S

Roen said:


> Is it common to find that bass response / impact is stronger on higher gain vs. lower gain for similar, volume matched levels?



I found that to be the case when I had lower level equipment. My Matrix M Stage and Fiio E12 had more bass on high gain than on low gain volume matched,  As I moved into gear with a better build quality, I no longer noticed that kind of difference.  My Audio GD NFb10ES2 sounds the same regardless of the gain setting, same can be said for my PB2 [r.i.p]


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## Roen

Mshenay said:


> I found that to be the case when I had lower level equipment. My Matrix M Stage and Fiio E12 had more bass on high gain than on low gain volume matched,  As I moved into gear with a better build quality, I no longer noticed that kind of difference.  My Audio GD NFb10ES2 sounds the same regardless of the gain setting, same can be said for my PB2 [r.i.p]



My LH Labs GO2Pro with the ES9028Q2M seems to have this difference between low, medium and high gain. I hope it's not considered "lower level".


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## castleofargh

Roen said:


> Is it common to find that bass response / impact is stronger on higher gain vs. lower gain for similar, volume matched levels?


it's possible for a few reasons. but what is most common is to come up with nonsense ideas about sound differences for lack of proper testing. if I had to vote for the most probable cause of audible sound changes with gain, I'd vote for that any day. 
some very smart people after conducting many tests have suggested that any listening test should be done within 0.1db. else the subjective impressions would most likely be tricked into interpreting the sound differently. I feel like different gain settings sound different, even now that I know I can't actually ear the difference and can barely measure it, I still feel like it's different. but if I care to match the levels and record the tracks, I then fail to pass an abx as long as I time align the song well enough(PITA). but that's my actual gear it's not conclusive about all gears of course. it just goes to show that trusting our subjective impressions when volume differences are involved isn't the best idea if you care about the truth. louder always feels like better bass. louder also straightens our equal loudness contour so the same signature doesn't sound the same to us. people who think they can still assess audio without proper volume level matching are fooling themselves. that is a fact and a very good reason to disregard most feedback from amateur audiophiles on the matter of how gain switches sound.

what could happen for real this time, could have to do with the amp itself in some designs when faced with some impedance. for example simply if the 2 gains don't have the same impedance output, and that happens on some amps, then many different causes could result in a different signature(audible or not). but those stuff are checked by measuring the signal into some specific load or measuring the output of the headphone with a microphone. random listening is more likely to result in wrong conclusions.

oh and IMO those stuff have absolutely no relation with how high end a device is.


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## Roen

castleofargh said:


> it's possible for a few reasons. but what is most common is to come up with nonsense ideas about sound differences for lack of proper testing. if I had to vote for the most probable cause of audible sound changes with gain, I'd vote for that any day.
> some very smart people after conducting many tests have suggested that any listening test should be done within 0.1db. else the subjective impressions would most likely be tricked into interpreting the sound differently. I feel like different gain settings sound different, even now that I know I can't actually ear the difference and can barely measure it, I still feel like it's different. but if I care to match the levels and record the tracks, I then fail to pass an abx as long as I time align the song well enough(PITA). but that's my actual gear it's not conclusive about all gears of course. it just goes to show that trusting our subjective impressions when volume differences are involved isn't the best idea if you care about the truth. louder always feels like better bass. louder also straightens our equal loudness contour so the same signature doesn't sound the same to us. people who think they can still assess audio without proper volume level matching are fooling themselves. that is a fact and a very good reason to disregard most feedback from amateur audiophiles on the matter of how gain switches sound.
> 
> what could happen for real this time, could have to do with the amp itself in some designs when faced with some impedance. for example simply if the 2 gains don't have the same impedance output, and that happens on some amps, then many different causes could result in a different signature(audible or not). but those stuff are checked by measuring the signal into some specific load or measuring the output of the headphone with a microphone. random listening is more likely to result in wrong conclusions.
> ...



Thanks for the informative post!


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## Makiah S

castleofargh said:


> oh and IMO those stuff have absolutely no relation with how high end a device is.



Good Point, to be completely honest, if my 3 amps, only my Audio GD NFB10ES2 has easy gain switching, and I don't DARE run my low impedance balanced Headphones out of High Gain... I have less than optimal volume control that way, of the times I've spent comparing and volume matching within 1db, sadly my Audacity reading doesn't give me decimals and I take a 2min sample [with a 1khz tone]  and average it to get the match. 99/100 times I can get an average measured output in audacity that's the same for each, but obviously that's not perfect 

still of the times I've done that, I don't notice a difference, but my iBasso PB2 and my Ember II, don't have easy gain switching,

so yea... still @castleofargh makes an excellent point


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## Pharmaboy

There's an entire thread elsewhere on Head-Fi about the effects of gain on sound. Some of the people posting to that thread have done fairly involved testing, incl. SPL matching of output at various gain settings so that volume fluctuation wouldn't be a confounding factor. I can hardly summarize all that here, but it seems to come down to the circuit design of a particular HP amp, whether gain will have any effect on sonic characteristics. 

Lower overall gain in a HP amp tends to encourage testing of this issue. I have a Matrix M Stage HPA-1 (w/o DAC), and played around with gain a couple times, trying to volume match the different gain outputs by ear (folly). I couldn't hear a consistent difference in bass or dynamics.

I went on an amp buying spree after that, getting 4 other amps w/more power than the HPA-1. A couple are uber-powerful (outputing 8-10 W/ch at one impedance value or another), and these totally discourage gain testing. With these powerful amps, it's difficult & risky to listen to efficient headphones on it w/higher gain settings (ie, fast track to deafness). I did try an inefficient headphone on the most powerful amps (ZMF Ori--a planar) at a couple gain settings. I heard nothing conclusive w/either.

Understand, though: I can pretty clearly hear differences between these amps on a given pair of headphones (they have distinct sonic characteristics, good & not-so-good). It's when I fiddle w/gain on a given amp that it gets harder to hear differences...


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