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-- New Monitors, Questions Regarding DB
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| Originally posted by Storyteller I don't get this reply, we've just been told quantitization/bitreduction does not concur when altering the volume within software as volume levels are relative. :S You can have 16bit audio with the max output set to 0dB, or 16bits between -inf and -30dB if you lower your volume. |
It does matter. Really glad you said that. Things are making more sense each post
. Getting smarter day by day :P
This is more how I see it.
It does seem obvious that when the sound is internal and volume is raised or lowered no voltage adjustment is taking place. Which therefore means the PC is adjusting the soundwaves which I would assume if you keep adjusting gain up and down throughout the signal chain would alter the sound in someway?
Is'nt that why ppl talk about having to set 'unity' gain so that signal in is the same as signal out until it reaches you monitor amp?
I am trying to understand the information provided on bit depth but I do have difficulty taking mathematical information and converting it to solid concepts in my head so bear with me lol
FJ
It really just doesn't matter if you got a 16-bit or above soundcard. The only time bitdepth matters is recording, and even then there are a few techniques to get rid of the noise (if any).
When I said relative I meant that in terms of signal to noise ratio. You can monitor a sound with 120dB of dynamic range at 0dB and at -10dB but it doesn't change the fact that it still has 120dB of dynamic range provided you keep the bit depth at 24 (120dB is the theoretical SNR at this bitdepth but lets just assume it is in practice to keep things tidy). It does not turn to 110dB when you turn down the master gain by 10dB.
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| Originally posted by camsr Listen, there's only TWO ways the soundcard is gonna lower the volume: Digitally controlling a solid-state amp circuit on the soundcards output circuit, AFTER the D/A conversion. It would be controlled by software drivers interfacing with the card. |
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| Originally posted by camsr It really just doesn't matter if you got a 16-bit or above soundcard. The only time bitdepth matters is recording, and even then there are a few techniques to get rid of the noise (if any). |
Just to be even more pedantic, truncating really means "no dither", just shave off the LSBs. Dithering is an alternative to truncation for reducing the bitrate.
I know, it's semantics, and that's what you meant. Just being an asshole. 
You would only use dither when you truncate bits so it doesn't matter. Dithering is not an alternate to truncating bits. It is a process you employ when you have to truncate bits (i.e. rendering down from 32bit float to 16 bit so that it is playable as CD audio) and the reason you would employ it is to add non cyclical noise to the recording to mask the quantisation error that occurs when you suddenly throw away 16 bits worth of dynamic resolution.
But now we are getting off topic so its probably best to just leave it at that. For anyone interested, Izotope wrote a pretty good, no bullshit guide on what dither is and why you would use it. Recommended reading as its actually written in plain english unlike some resources on the subject.
Theres also some info about bitdepth and dynamic resolution which will help those who are still confused about gain control and why bitdepth does not reduce when you lower gain.
You can find the guide on their website and its in PDF format so you need Adobe Acrobat Reader.
Let me point out that there are two different digital domains to be considered here: integer and float. ...and there are two ways to degrade sound quality by digitally amplifying.
You will not loose quality by amplifiying by powers of two if you are in float domain, as this will leave the bits of the mantissa untouched and just increase/decreaese the exponent. In float domain the full scale value is defined to be 1.0 but there is no rule that would prevent your soundcard to produce meaningful voltages above greater values.
In integer domain the maximum integer value represents the maximum voltage your soundcard can output. Any (theoretical) value larger than your available bits will be clipped. Digitally attenuating before the DAC means using less bits no matter what. You WILL loose bits in integer domain as they will be shaved off. This might not be of any relevance if the original signal was normalized and you are attenuating no more than 10dB. But if the original signal was recorded at say -12dB and you digitally attenuate the output by another 12dB (reducing the percieved volume to little less than a half) your SNR will be at best 72dB. Given an average soundcard there will definately be audible noise if analog output is set to produce moderate 95dB(A).
In any digital domain amplifying with factors other than 2 will cause roundoff errors depending on your signal and the resolution of your amplification factor. This is a very slow process but will get get audible eventually... btw: this is one of the reasons some digital filters sound shit.
Production hosts normally operate in 24 or even 32bit floating point domain. So amplification and attenuation might not matter a lot but as soon as you output or render all this will be converted to integer domain.
btw. it is hard to find analog equipment that has a realistic SNR of more than about 95dB. Built in soundcards especially in notebooks are even worse as they will catch digital noise coming from the electronic components of the computer. In PA you migt even find 85dB and less. But Average signal dynamics in electronic music hardly exceed 60dB so you might even get away with 12bits of resolution without hearing quantisation noise.
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| Originally posted by Derivative You would only use dither when you truncate bits so it doesn't matter. Dithering is not an alternate to truncating bits. It is a process you employ when you have to truncate bits (i.e. rendering down from 32bit float to 16 bit so that it is playable as CD audio) and the reason you would employ it is to add non cyclical noise to the recording to mask the quantisation error that occurs when you suddenly throw away 16 bits worth of dynamic resolution. |
In math, truncating a decimal means you just keep the integer part and throw away the decimal, i.e. take the floor even if the value is closer to the ceiling. In audio, it means you just pretend that all the extra bits are zero and slice 'em off.
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| Originally posted by DigiNut You're still propagating the same patently false nonsense about losing bits though. It just doesn't work that way. Good digital devices never use any fewer bits when attenuating the signal, they just change the reference level that corresponds to the signal maximum. Before the DAC, you change the signal reference. After the DAC, you alter an op amp. |
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You're also wrong about roundoff error. Integer division might introduce an error, but not necessarily. It's only in floating-point math where you might multiply two perfectly accurate numbers and end up with an inaccurate one ("0.4" is not perfectly representable, for example). In practice, though, the error is so small that it won't make a difference. 0.4 comes out as 0.400000000002 or something like that. |

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Converting from floating point back to integer is an issue, and that's what the dithering algorithms in software are for. UV22HR does a great job of making the change almost completely transparent. Waves IDR does it pretty well too. |
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| Originally posted by halo I'm talking integer here as I'm currently aware of no output device that supports float output. Integer does not have any reference or exponent. Take a 16bit fullscale sine, devide by to, thus truncating the LSB, multiply by two to restore original level. The LSB might be stuffed with zeroes or dither noise, in any case although your data has never left 16bit integer domain the information contained is left at only 15 bits. |
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| Digitally controlling the output gain of the DAC is not what I understand as digitally amplifying/attenuating... and it's not the way most players do their output attenuation (winamp might, but i don't know) |
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...and your contradicting yourself ![]() |
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| btw: integer division does nearly always introduce error. As it's rather uncommon that you devide by a common factor. |
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| dither does not get rid of errors it's efficient in masking them ...by introducing even more errors (also known as noise). |
blah blah blah blah......
is all I hear hahaha jk what are you guys talking about!!!!!
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| Originally posted by DigiNut I've heard this bizarre assertion about "bit loss" several times and still can't understand where it could possibly have come from. It's completely untrue, and my only guess is that it must have been something spewed by a marketing weasel that got misinterpreted by a few viewers or buyers. Bit depth in the digital domain is a constant 16-bit, 24-bit, or 32-bit floating-point. Period. There are no bits "removed" when you lower the volume, nor is there ever a scenario where you "don't get the full 16/32 bits" (this is not like a motor assembly where you only get 90% efficiency, you get 100% of the swing in a digital signal). Only exception is when you're using a bitcrusher, but that's obviously a deliberate bit reduction (duh). In actual fact, it's much better to use software to reduce gain because there's no noise. In the analog domain, if you have a noisy stage that outputs low gain, and you amplify that at the next stage, you're amplifying the noise with it. This is a non-issue when working with digital audio. |
Very interesting thread, but there's so much contrasting information.
I can't really add to it, because my output is turned halfway down in windows, and halfway down on my monitors... now I'm actually doubting the way I'm handling my chain.
I'm going to play around with various settings and see if I can actually hear any audible difference in sound quality.
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| Originally posted by kitphillips I think I know where this issue came from; when you record audio into the digital domain, you should attempt to do it at the highest level possible, in order to make the best use of your bit depth. try recording something at low volume then boost up the volume (say in ableton live) and you can see on the waveform that it is very sort of "quantised" looking almost, sort of jagged. Also, Remember that it is common practise to dither your work when bouncing down, I don't know if that means that this also applies to output... either way, I doubt whether it makes a significant difference! At the end of the day, monitoring can be done quite well with very little, Chicane did the whole of behind the sun on a pair of monitors powered by a teac amplifier, he did quite well from that album I believe... |
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| Originally posted by DigiNut You're confusing reference with mantissa. What I'm talking about is using one 16-bit word (or two, in stereo) to represent the signal, and another 16-bit word internally to represent the swing. It's still a 16-bit signal on the input and output, but there's more to it than that inside the device. |
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| I can't say for sure that every digital device does this, but doing it that way will never run into the scenario you speak of. |
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| Software always uses floating-point internally anyway, which is the "digital" that most people here are talking about, so the integer division issue is a moot point.And since most VAs today are just software on the inside, they have the same characteristics. |
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I should also point out that the actual level of "noise" we're talking about here (i.e. miniscule), if one accepts that it even exists, is no larger than the THD characteristics, line noise, and other nonlinearities introduced by the op-amps in analog devices. Worse, in the analog domain, you don't even have to apply any gain - even with unity gain you'll still be adding noise. It's very, very rare that 24-bit or even 16-bit DSP would introduce more noise than doing it in the analog domain. I've never seen it happen in practice and I've never seen a good theoretical explanation either. |
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| I'm not sure exactly how the internals of WMP or Winamp work, but I know that what you're saying is not correct in this instance because I can turn the volume on either one of the down to just one notch above the minimum, and still hear zero distortion on the output. Again, by your logic this would be limiting the signal to 1 or 2 bits. Obviously this would be heavily distorted, and obviously, this is not the case. |

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| How so? |
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| Integer division might introduce an error, but not necessarily. It's only in floating-point math where you might multiply two perfectly accurate numbers and end up with an inaccurate one |
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| You're also wrong about roundoff error. |
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| Again, where's your proof of this? |
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| That's true... more or less. It doesn't introduce "even more" errors, it introduces a different kind of noise, but it's the exact same amount of noise as truncation. In any event, I never said that dithering gets rid of errors. I just said that's what used when converting floating-point signals back to integer signals, and if you're only ever doing that once in your signal path (which is usually the case), the noise will never be audible with a good dithering algorithm. |
..as long as you can swear to god that none of your components does any conversion... EVER... i for myself wouldn't count on that... an i do reuse sampled data.
To make my point clear...
1. usually it's hard to hear digital noise
2. bit loss does happen
3. it might not be obvious in your configuration
4. you can demonstrate bit noise by simple integer division... that's what bitcrushers do
5. you'll have to push your gear to make it audible, but it's only two clicks and a twist to get as far away from digital noise as you can.
6. "...but it normally works" is no excuse for bad design...(see Microsoft)
last but not least: in a normal home listening environment 12 bit (about 70dB) SNR is way more than your dynamics should be. That would be about 100dB peak amplitude over a quite moderate backgound noise of 30dB (most computers push background noise to about 40dB)
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| Originally posted by Derivative Sort of but not quite there. If you are taking any analogue signal and converting it to digital (i.e. recording from a mic/guitar to a soundcard input) you want to record to the highest bit depth and samplerate you possibly can. Increasing gain has no effect on quantisation. When you record a sound and play it back in a wave editor increasing gain just increases the vertical height of the waveform as this is just a graph of amplitude over time. Its frequency is represented in the number of full oscillations per second. So it can make a wave sound appear more 'jagged' but only because you are stretching it vertically. On the issue of pre gain and post gain this is to do with mic/instrument and line level devices. When you record from a guitar to a line level soundcard input there is an impedance difference and a peak level difference. I forget what the impedance difference is but its something on the order of 10,000 ohms I think. Don't quote me on that. The peak level difference is on the order of 40 to 60 decibels. If you record a mic or a guitar straight into a line level input with no preamp stage, you have to apply about 40 to 60 decibels of post gain to the recording - which will increase the noisefloor in proportion to the peak signal - basically there will be lots of hiss and low level noise but its now 40 to 60 decibels louder so you can hear it really badly. If you don't apply 40 to 60 decibels of post gain then you are just left with a recording so quiet that it is for all intents and purposes unusable when composited with other sounds recorded from line level devices. On the issue of dither. You don't dither when you bounce. You only ever dither when you are bouncing down to a lower bitdepth. If you are recording at 32 bit float and you bounce to 32 bit float you should not dither. However, if you record at 32 bit float and bounce down to 16 bit you will need to dither but you do not want to dither more than once as this process involves adding low level noise to a recording. This noise is cumulative. This is why the most common advice you will get about dither is to work at the highest bitdepth you can for as long as you can and then when everything is done, you dither down to CD Audio bitdepth as the very last process. But only if that mix is destined for 16 bit CD. |
Although, if this is the case, why does the waves L3 multimaximiser(ducking head from flames) use dithering? Should I turn this bit off perhaps?
I don't know why certain Waves plugins have the option to apply dither on the output. I'm talking about the L series limiters and the Linear Phase Equalisers. The dither won't be applied until you bounce the output so for the love of god turn dither off if it is enabled. The only time you want dither on these plugins is if you have a finished, mastered tune and L3 is like the last post processor in the signal chain.
Also, if you use for instance L3 and Linear Phase EQ in your mixes with dither on, then slam your finished mix through Izotope Ozone or some other mastering app with dither on, this will add at least 3 times the amount of dither noise to your mix which is horrendous.
Its best not to bother with dither until you mixdown is spot on and you are a dab hand at mastering recordings. I don't even concern myself with dither and always turn it off where it is available.
I'm not even going to try to understand anything you guys just said. What was the final verdict? Does reducing the volume in your ASIO mixer software reduce the quality comming out the speakers or not?
Thanks 
Short and Sweet: Yes.
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| Originally posted by camsr Short and Sweet: Yes. |

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