don't know the numbers for todays audio DAC chips?
better audio DAC can manage ~20 bits dynamic range, the best advertised monolithic is 132 dB (A weighted) ~ 22 bits
so there is actually enough room above the better 24 audio DAC electronic noise for 20 dB attenuation of 16 bit source without "bit loss"
and differential linearity of better Delta-Sigma extends well below the noise floor
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I know "numbers" ,but also I have personal experiences from direct listening comparisions of booth methods, also measured data, background noise and disturbacies are very different. Simply I am missing (and many other listeners too) "black" background with attenuation in digital domain. But it may be for someone "enough", why not..
Try in some quality sound editor convert 16 bit recording to 24bit data, than attenuate in digital domain e.g. -20-30dB, (often used volume settings at listening), and than play it without analogue attenuation, with same SPL for booth cases. Is sound the same for You?
Try in some quality sound editor convert 16 bit recording to 24bit data, than attenuate in digital domain e.g. -20-30dB, (often used volume settings at listening), and than play it without analogue attenuation, with same SPL for booth cases. Is sound the same for You?
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We sometimes call it a "Silence between (or below) tones" and it is related to S/N of spurious, usually non-harmonic spectral components.
Jcx, you can definitely make your own measurement of the digital volume control set at -30dBFS. Such measurement must be done with high resolution test system. Datasheets are not telling the whole story.
Jcx, you can definitely make your own measurement of the digital volume control set at -30dBFS. Such measurement must be done with high resolution test system. Datasheets are not telling the whole story.
elektroj said:
And what are you going to do about the front end due to fact that modulator runs off of a single +5V supply? Coupling caps?
Indeed, analog volume control also worsens the S/N ratio (except maybe when you use a 1kW pot immediately before the speaker).
Taking a whitepaper from an analog volume control manufacturer as proof that digital is 'bad' - I don't know
jan
BV, youve got some pretty messed up gain structure if you need to attenuate so much you can hear the noise floor.... the 'numbers' are real, that is how it works, if you hear something else before youve started effecting the data, then you are hearing things that arent there i'm afraid. this is not theory, this is not bleeding edge, this is how the production world has been doing it for decades, but some of the audiophile community are still hanging onto information that is either incorrect, or outmoded long ago...
certainly the last 5 years or so has seen Dacs, DSP and software that utilizes digital volume that provides enough buffer for anyone who doesnt have too much gain. anyone with that much gain is introducing noise and distortion, non-linearities aplenty already without digital volume.
certainly the last 5 years or so has seen Dacs, DSP and software that utilizes digital volume that provides enough buffer for anyone who doesnt have too much gain. anyone with that much gain is introducing noise and distortion, non-linearities aplenty already without digital volume.
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Indeed, analog volume control also worsens the S/N ratio (except maybe when you use a 1kW pot immediately before the speaker).
Taking a whitepaper from an analog volume control manufacturer as proof that digital is 'bad' - I don't know
jan
Actually it does not have to. One of the things on my list was to show the use of an analog volume control that improves the S/N ratio as the volume is decreased. But then you probably already know how to do that.
Yes,analog chain S/N, but not the ratio Signal to (D/A conversion artifacts+I/V + LP filter noise), which is the case with digital domain attenuation, and is subjectively much worse..
qusp
I am using preamp with gain 6dB, power amp with gain about 30dB. Do You mean, that it is too much? And normal listening level is somewhere between -30 to -20dB at preamp.
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Thanks BV for the paper. It looks like just the thing to start with.
As you know, because many passive volume controls are being phased out, the reasonable alternative of the motorized pot, rather than an electronic volume control, is becoming more and more difficult to implement in new products.
Just grabbing the first electronic volume control and 'believing' its spec sheet fully, without further testing, is one of the reasons why there is so much mid fi disguised as hi end in the marketplace today.
What happens is that a perfectly good designer decides to go 'modern' with digital controls, etc., etc. The analog designer (like me) isn't as used to digital products, because the designer has been fully engaged in analog design for years, but now must 'upgrade' to the new digital additions to his product.
Real care in knowing what the spec sheet really tells you, independent measurements to find hidden 'glitches', and a first class playback listening system, are all important, if 'disaster' in a 'sound quality' sense does not happen, and it happens often enough, trust me.
As you know, because many passive volume controls are being phased out, the reasonable alternative of the motorized pot, rather than an electronic volume control, is becoming more and more difficult to implement in new products.
Just grabbing the first electronic volume control and 'believing' its spec sheet fully, without further testing, is one of the reasons why there is so much mid fi disguised as hi end in the marketplace today.
What happens is that a perfectly good designer decides to go 'modern' with digital controls, etc., etc. The analog designer (like me) isn't as used to digital products, because the designer has been fully engaged in analog design for years, but now must 'upgrade' to the new digital additions to his product.
Real care in knowing what the spec sheet really tells you, independent measurements to find hidden 'glitches', and a first class playback listening system, are all important, if 'disaster' in a 'sound quality' sense does not happen, and it happens often enough, trust me.
Few mfr will give thd spec below 0 dB. And, spec which only give an A weighted number is clearly suspect to begin with. No calc should be made with A weighted number as a beginning point.
As designers, we owe it to ourselves to measure against the claims under conditions of actual use. As a minimum, that would require thd at realistic levels... -20-30 db below max and it isnt asking too much to expect to have clean signal levels-30 below that level... Or -60dB. This should be done as S.O.P. here before debating. Using marketing numbers and conditions as a basis for arguement is foolish and misleading.
Thx-RNMarsh
As designers, we owe it to ourselves to measure against the claims under conditions of actual use. As a minimum, that would require thd at realistic levels... -20-30 db below max and it isnt asking too much to expect to have clean signal levels-30 below that level... Or -60dB. This should be done as S.O.P. here before debating. Using marketing numbers and conditions as a basis for arguement is foolish and misleading.
Thx-RNMarsh
For the reasons you have just described, I built a measuring amplifier with gain 40dB to be able to measure noise level of preamplifiers and make FFT analysis (noise level which is normally below common audio measuring system threshold) and to be able to measure at low output level. My SW computes unweighted integral noise in 20Hz - 20kHz band, so no tricky "noise bottom" like -150dB etc, which depends on bin width (number of samples in FFT, sampling frequency and possibly averaging as well). Noise of the measuring amp is attached. So I amplify the preamp output by 40dB, measure noise and ten subtract -40dB to get preamp's noise. I also measure distortion, at about 10 - 20mVrms of preamp output voltage. I have not measured any increase of harmonic distortion at low signal output level, but found differeces in noise of preamplifiers and its spectra.
With this method, I can measure noise level down to -126dB/ref 1Vrms (20Hz - 20kHz, unweighted). The best preamp I measured had noise -115dB/1Vrms unweighted, 20Hz - 20kHz. The gain of that preamp was 14dB.
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Indeed, analog volume control also worsens the S/N ratio (except maybe when you use a 1kW pot immediately before the speaker).
Taking a whitepaper from an analog volume control manufacturer as proof that digital is 'bad' - I don't know
jan
As oppose to white paper from digital manufacturer ...
As oppose to white paper from digital manufacturer ...
Quite. Whitepapers are marketing instruments, whether from 'digital' or 'analog' manufacturers. You see the same trend in data sheets. You're not supposed to lie in data sheets, but nothing prevents you to emphasize the strong points and do the measurements at favourable conditions.
jan
OPA with offset.And what are you going to do about the front end due to fact that modulator runs off of a single +5V supply? Coupling caps?
I don't understand the matter of all this discussion about evil digital calculations.
As long as the errors (rounding) are under the noise floor, (that you can't hear) what the matter ?
With 32 bits, you can attenuate by 60db without any audible artifacts. What the hell ?
Don't you think that analog distortion+noise is not an error as well ?
I think we would have to bring Scott into the discussion about data sheets but I don't completely agree with the disregard to a data sheet or white paper. If we did not have at least this basic information we would be completely in the dark about so many products. We need to start somewhere and the data sheets and white papers at least give us a basis to start our selection process. If you had neither of these what would you have to do, inspect and test every single device against every other device before you could even start to conceive of a design? Yes you will need to test and confirm the information, but you do need something to at least weed out the devices that the data sheets will at least tell you are inappropriate. From there of course you need to do your do diligence to make final selections.
They do help, you can learn all kinds of interesting things from whitepapers. As an on-topic example, there was a Cirrus whitepaper on the Jeff Rowland site discussing the design of their CS3308-family of analog volume controllers. I found it facsinating how they contour the shape of the substrate underneath the cmos ladder switches to cancel the voltage coefficient, so they can get to 0.000xx % THD of the control.
That doesn't proof it is better than any other volume control, but it is an interesting insight.
Edit: it was the resistors that were linearised, not the switches.
Also, they switch the comp cap with gain changes.
See http://jeffrowlandgroup.com/kb/categories.php?categoryid=147
jan
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If your system is able to produce 120dB spl (no need for more pain), and, considering that 30dB spl is the noise floor of your quiet listening room, 60dB is the max attenuation range needed for a full volume control.
That is the reason why CD used 16bits of definition (96dB). And, as far i'm concerned, it is enough.
With 24bits, you keep 48dB of margin for a attenuation (witch will be enough for HIFI listening at a correct level). Then, you can set an analog 30db attenuator to bring the max at your comfortable listening position and keep a huge margin of definition..
With 32bits, you have 192 dB of dynamic. it let -you 96dB of margin for the level attenuation...hum.
That is the reason why CD used 16bits of definition (96dB). And, as far i'm concerned, it is enough.
With 24bits, you keep 48dB of margin for a attenuation (witch will be enough for HIFI listening at a correct level). Then, you can set an analog 30db attenuator to bring the max at your comfortable listening position and keep a huge margin of definition..
With 32bits, you have 192 dB of dynamic. it let -you 96dB of margin for the level attenuation...hum.
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