Source Volume Vs. Amp Volume

Discussion in 'Portable Headphone Amps' started by az greg, Dec 30, 2008.
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  1. Joris
    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).
  2. 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.   
  3. HiFlight

    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. 
  4. TheHighBuilder
    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.
  5. DaniXFI
    Bump, wondering the same.
    I guess it's not much important since everyone has its own opinion :S
  6. holden4th
    From my PC using Fiio E7/E9 I always set the source (Spotify, Music files, etc) to max volume as it is a direct digital stream to the DAC/Amp.
    On my iPad which uses an analogue out (HO) as I don't have the camera kit I set the volume to about 70-80% and let the Fiio Q1 do the work from there.
    When Fiio produce an LOD that works with the iPad (coming soon apparently) I'll up the source volume to 100% if the LOD allows it.
    I've always used any digital source this way. My CD player has a volume control which I set to max. and this works perfectly well with my HiFi system. They're probably designed this way.
  7. c64
    Low volume on pc/soundcard and adjust headphone amp is the way to go.
    No idea why people go around saying put pc volume at 100% and adjust amp, they are just wrong.
    You will get distortion and clipping the higher you go.
  8. streetfighter
    Would like to bump this thread again, as I have the same question. Not sure which way is right or wrong?
  9. barrec
    I just recently got into head-fi and wondered this very thing. My instinct is that the source should be quieter than the DAC since the DAC is the equipment influencing the sound. I have noticed with my Oppo Ha-2, however, that my iPod's volume automatically goes to max every time I turn on the DAC while they are connected. I wonder if it is coincidence or if the DAC is set to receive max input volume from the source.

    The other component I've been considering is the headphones. I can't fathom cranking my iPod all the way because I would only turn the DAC volume to 2 at the most. On the other hand, if I had better headphones that required the built in amp, I may very well see the need for max source volume.
  10. subwoofer
    As I am about to enter into the world of headphone amps, This thread caught my eye and I've read all the replies so far.
    Before I get going, excuse the low post count here. I have a long obsession with all things audio and used to test/review for a car stereo magazine, and have a M. Eng, so know a few things (and also don't know a lot of things).
    Possibly important enough to be a sticky if some sort of definitive answer can be found.
    I'm going to disagree quite strongly (although actually 100% output may be slightly too high, perhaps around 95%), and part of the reason is based on the loading of the circuit.
    When using a headphone jack (due to there being no line-out), that headphone jack needs to be taken up to near the maximum output to get near the voltage levels of a line out. Most amplifiers are designed to work with that level as their input. anything lower and you need to take the amplifier up to near its maximum to get the level you want (because you made the input level too low).
    HiFlight's quote is spot on as it comes down to S/N ratio, continued below the quote...
    So, whatever your view might be, your final stage amplification will be amplifying everything from the input. All devices have some noise, so noise cannot be ignored.  If the amplifier is taken to near to its top end of amplification, it will be making that input noise the loudest possible level it can be, so you WILL hear it.
    This means that you definitely do want the strongest 'clean' input signal with the highest S/N ratio you can get without distortion.
    The critical factor here is with a headphone output, it is designed to run a high load (low impedance) so can deliver current to drive the coils of the speaker. When connected to the input of an amplifier, the impedance is much much higher (~10kOhm), so it draws very little current (the lower current the better) and is better able to avoid voltage sag and clipping.
    There is no way to determine the correct level to set the headphone output using headphones to 'listen' for distortion, because as soon as you remove the load, and perhaps use an oscilloscope to monitor the output for clipping, the output will recover and no longer clip.
    One could argue that the characteristics of the headphone output's amplifier can be avoided if running it at a very low level, but you definitely will end up with a low S/N ratio and you will hear hissing.
    Using a headphone jack as a source is often the only option, but these can remain distortion free to a far higher level when connected to a line-in than when they drive a low impedance load.
    Interestingly there is an analogy to the source/amp level configuration in the car hifi world as all power-amps are designed to sit at a fixed gain and the volume is then controlled by the source components, However, a critical point in this case is that all the components are designed specifically to run like this. (Of course so are pre/power-amp HiFi systems). IF, and I really mean IF, a headphone amp was supposed to be used like this, then it would not have a volume knob on it; there would be a relatively inaccessible 'gain' control that you set once and leave.
    I am open minded about this, but reviewing these facts, I just can't see a good argument for using the headphone amp at maximum volume and using the source to control the output level.
    (A small note regarding 100% settings - generally I would avoid ever using something at 100% as fully loaded you are more likely to see/hear the subtle differences in some components. I would go with 90-95% as a practical maximum in most cases.)
    Hard to say without knowing about the audio file. The best way to do it would be to use a gain control loop in SW which gets you close to full scale on the digital side... That way you're not leaving any bits on the table and you don't have to worry about clipping either, since the control loop will handle it. If I had to guess, I suspect this is probably how that replay gain stuff works.

    Sent from my E5803 using a highly trained, special forces carrier pigeon
  12. bunnynamedfrank
    sooooooooooo whats the bottom line on this one gang? I have itunes all the way up, computer volume all the way up, amp at the level i want.. i don't seem to hear any distortion but then again i dont have golden ears....  i think after this conversation we should discuss what people think about upgraded cables :p

    The best option would probably to back off the max volume a little bit. You'll minimize the loss of dynamic range and reduce the risk of clipping.
    You also want to make sure your amp is well below the 1dB compression point... You can get some funky distortion in the non-linear section of an op-amp. I'm sure most amps are designed so that max gain is well within the linear region, but better to be safe than sorry. You're probably well above safe listening levels here anyway.
    So back off the max volume on your DAP a little bit, and make sure you don't crank your amp all the way up either.
  14. bunnynamedfrank

    I'll give it a shot!
  15. money4me247 Contributor
    actually I thought it was the opposite.
    I was under the impression that when your computer volume set at 100% that is the normal volume of the track and that is when you are getting nominal line level output. any volume changes below 100% is digital attenuation (reduction of the strength of the signal). when you digitally reduce the signal, sometimes the result has to be rounded off. aka 4-bit value of 13 halved by digital attenuation would result in 7 (since 4-bits words has to be represented by whole numbers), so that is not as accurate as the original 15.
    I believe you can get digital clipping is if the software processing the amplitude of the signal goes beyond largest positive value that can be represented. aka when a value of 2000 is doubled to 4000, but the maximum value that can be represented is only 3000. but I don't think that would happen with most recorded songs unless you artificially alter the signal strength.
    There are programs that can push the digital volume beyond the 100% and that is when you get issues with clipping and distortion. Programs like MP3gain would be an example would digitally alter the signal to boost volume which can lead to distortion. Sound enhancements like loudness equalization or "set volume for all songs the same" options can push songs above 100% which can create distortion, so best turn it off those enhancements.
    what I've always heard was to max source, max media player (only to 100% as some programs can go above that with >100% settings or dB boost settings), and control volume with amp only.
    basically the concept is that you want to leave the digital volume alone and only play with the analog volume control. (edit: and if you are worried about software processing, then perhaps have the media player volume a bit lower but I am unsure about this)
    however, I am not an expert on the topic, so I would love to read other people's thoughts.
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