Source Volume Vs. Amp Volume

Discussion in 'Portable Headphone Amps' started by az greg, Dec 30, 2008.
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    Have you generated a test file, played it out at max volume, and recorded it so if it really is at full scale or gained?

    I haven't. So I wouldn't risk it.

    Sent from my E5803 using a highly trained, special forces carrier pigeon
  2. money4me247 Contributor
    ??? I am not sure I understand you.
    I was just saying that you should control volume with your amp first and if you have issues then music player, leaving the computer volume at 100%.

    Sorry... my phone thinks it knows better than me and tries to autocorrect things, despite the fact that I have that feature disabled.
    I was asking if you had generated test files at a known amplitude, then played it out of your DAP at full volume and recorded the output, then processed the captured data to see if the DAP played it out at the expected level or if it applied a gain.
    You'd have to know the characteristics of the DAP and audio capture card front ends to figure it out. I don't think it's worth the effort, so I haven't done it myself... and since I can't be 100% positive what the behavior of my source is, I don't think it makes sense to risk the chance that the audio may be clipping by setting the volume all the way up. I balance the desire for more dynamic range with my worry about clipping by backing off the volume a little bit. I think it makes the most sense without having all of the information.
    I saw something in your post about rounding... I didn't mention any thing before... but there is probably rounding all over the place through the DSP chain on the source. DSP is particularly prone to substantial bit growth because of how many operations require multiplies... There is likely rounding at multiple stages. There are, of course, methods for rounding that will help minimize the impact. For example you could dither the truncated bits before rounding to randomize whether you round up or down, you could round to the nearest even so you don't skew the mean value, etc. And halving 13 does not automatically mean you have to truncate to 6 (or round up to 7)... DSP is done with fixed point math, 6.5 (more specifically 13/2) can be represented in 6.1 format (6 bits, one of which is fractional) as 001101.  
    money4me247 likes this.
  4. macky112
    not trying to revive an old thread, but I stumbled upon this thread when I googled "headfi PC amp max volume"

    after reading through this thread and did some tests myself, here is what I found:
    source volume (ie phone, DAP, PC etc) should play the loudest possible without clipping, and on my PC, that is about 50% volume, YMMV

    so bottom line is, there is no magical volume you need to be at, each source has it's clipping threshold, and you gotta find it for that particular source.
  5. theveterans
    Source volume is disabled if you bypass Windows Mixer through WASAPI or ASIO, and this plays music at the source file volume levels (i.e. no alteration of the bits via software EQ, DSP, software volume control).
  6. lowrider007
    I was always under the impression that having the PC volume set at 100% was the equivalent to a fixed line level output, true or false?

    Also can't this be tested by playing a CD on a PC plugged into an amp and then playing the same CD on a CD player outputting from the RCA's into the same amp?
  7. theveterans
    If the output is digital, it's true as long as the DAC's line out is fixed. On analog or using on-board audio, it depends on the model. Some only provide .5V or 1V rather than 2V
  8. Senman
    I have my sens 650 and old schit vali connected to laptop , and I always turn my amp all the way up and adjust on pc.
    That way I hear all the registers with equal value and all that;s left is the prefered volume.
    Last edited: Feb 18, 2018
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