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Digital vs analog volume control

Discussion in 'Sound Science' started by shaocaholica, Nov 11, 2013.
  1. shaocaholica
    Does it really matter?  The way I see it, if you lower the levels on a digital signal before it gets sent to a DAC its as if it were done during mastering so unless you're playing back really really loudly it shouldn't really make any difference whether you control volume at the source (digitally) or at the amp (analogy), right?  Its not like you can hear the difference if the absolute output volume is kept the same right?
  2. KamijoIsMyHero
    I am not sure about all digital volume control but the way volume was controlled when I implemented in an FPGA was destruction of bits (note: bad) to lower volume and addition of bits (note: also bad) to increase the volume which started to distort the music. I am pretty sure the VLC player does the same which is why it distorts when you set the volume past 100%.
  3. shaocaholica
    That's the question though. Is the reduction of sample value audible vs analog attenuation? It looks bad on paper but what about in practice?
  4. KamijoIsMyHero
    Like always, try it for youself to see if you can hear a difference. Your experience will matter more for you that other people's experience. I hear a difference going from VLC to Foobar and digital vs analog. A small difference...but maybe it's just placebo...
  5. bigshot
    If modern electronics can't even make a clean volume pot, we're all in a lot of trouble. Honestly, people worry about the most trivial things.
  6. stv014
    Everything distorts (clips) if you ask it to output higher volume than it is capable of. This is also true of analog devices. Some software volume controls dynamically compress the sound to avoid clipping, but this still degrades the quality.
    The "loss of bits" with digital attenuation many people are worried about is not much of an issue for 24-bit output, and that is supported by pretty much any decent DAC these days, even onboard codec chips. Additionally, software volume controls can easily implement dithering, but this is unnecessary at 24-bit resolution.
    Digital attenuation does reduce the dynamic range of the DAC, but a modern DAC usually has more than you need anyway, so reducing the level by up to 10-20 dB can be OK if you have 110+ dB dynamic range at full volume. Or even more for quiet listening, since the noise floor will still stay below the threshold of hearing.
  7. xnor
    With the analog gain set low enough .. I don't see a problem.
  8. Thujone
    I sent my Emotiva mini back on an RMA due to a channel imbalance which I found (after an engineer explained to me on the phone) was only because the pot is not guaranteed to have a perfect balance until turned up past the low extreme (9:30 for me), which is crazy if you are using it for headphones and not speakers. In this case, the OP's question is the same one I have. Is there any quality issue when lowering the gain in iTunes in order to get more play out of the pot?
    As always, I'll have to see for myself. Whenever the amp shows back up...
  9. xnor
    Analog pots can be all over the place in terms of channel balance at high attenuation unless you select for the better ones. That's why I always tell people to get the gain right, so they don't need high attenuation but can actually use a big range of the pot..
    But no, they need an ultra hot nonstandard source and headphone amps with gains similar to small power amps... and then they wonder why their highly sensitive headphones are so loud.
  10. proton007
    I think there are other issues as well. If you live in a humid climate, electronic components sometimes deteriorate. Especially contacts and relays.
  11. ab initio

    Usually, it doesn't matter : (explanation)
    Thujone likes this.
  12. sgrossklass
    Digital attenuation at sufficient precision (24 bits and up) can be regarded as transparent. Thankfully so - I like ReplayGain!
    That said, the total dynamic range provided by an oldfashioned analog volume control / amplifier may be 130 dB or more. Achieving that sort of performance in a DAC in real life is not impossible nowadays but requires a fair bit of effort. Besides, noone really needs that amount of instantaneous DR in audio, it's just that you'd like to have 70+ dB of DR available regardless of whether super-sensitive IEMs at more than 130 dB/V or 600 ohm oldies at barely 90 dB/V are connected. This is why you can use an old trick: Multi-stage volume control. In this case the DR requirements for each individual stage may be a lot more relaxed. That's how DAPs get along fine with seemingly-modest 95 dB DACs - they follow them up with PGAs (electronic volume controls). Higher-DR stages simply need more power (and if that just means higher supply voltage(s) at similar current), and that's obviously at a premium in a portable device.
    Soundcards with super-duper measured performance usually employ plain DACs without an integrated PGA but rarely bother to employ an external one (some rather well-performing ones are available, though obviously it's a bit hard to compete with a plain amplifier stage). The result: Stuff like the Xonar ST(X) starting to hiss on the headphone out when DAC SNR is compromised to a "mere" 108 dB at 44.1 kHz.
  13. castleofargh Contributor

    best and most complete explaination I have ever seen. (first half of the video)

    to make it simple digital volume control is a problem only when you need to go really really low, and the major points to consider are noise floor of your source and if it's 16 or 24bit.
    personnaly my choice really depends on that noise floor. if I don't get bothered by noise I prefer digital control as I avoid channel imbalance and have a very precise volume control on IEMs.
    but if I hear noise I sell the gear or add an amp so in both cases volume control doesn't matter anymore ^_^.

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