John Curl's Blowtorch preamplifier part II - Page 3415 - diyAudio
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Old 4th February 2013, 10:26 AM   #34141
jcx is offline jcx  United States
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Quote:
Originally Posted by BV View Post
Esperado, qusp
Citation from oldier Wolfson white paper , claryfying my word "suboptimal"
Always will be regulation in digital domain acompanied with relative increasing of quantizations errors and partially loosing of informations. You can manipulate 16 bit data with 32 bit resolution, but if you need e.g. 20dB attenution, lower valid data from original information get lost...
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

Last edited by jcx; 4th February 2013 at 10:35 AM.
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Old 4th February 2013, 11:05 AM   #34142
BV is offline BV  Slovakia
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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?

Last edited by BV; 4th February 2013 at 11:08 AM.
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Old 4th February 2013, 11:20 AM   #34143
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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.
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Old 4th February 2013, 11:49 AM   #34144
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Originally Posted by elektroj
Do you mind to tell us which ADC specifically it will be?
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Originally Posted by Esperado View Post
AKM 5394 ?
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?
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Old 4th February 2013, 12:22 PM   #34145
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Originally Posted by fas42 View Post
People have this bizarre notion that somehow analogue S/N is always "magic", but digital S/N is bad, really bad. Well, I have yet to be offended by "poor" digital S/N, but my ears have been savaged by vile, offensive analogue S/N far, far too many times ...

Frank
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
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Old 4th February 2013, 12:32 PM   #34146
qusp is offline qusp  Australia
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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.

Last edited by qusp; 4th February 2013 at 12:41 PM.
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Old 4th February 2013, 02:24 PM   #34147
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Originally Posted by jan.didden View Post
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.
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Old 4th February 2013, 02:29 PM   #34148
BV is offline BV  Slovakia
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Indeed, analog volume control also worsens the S/N ratio
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.

Last edited by BV; 4th February 2013 at 02:31 PM.
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Old 4th February 2013, 02:31 PM   #34149
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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.
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Old 4th February 2013, 02:33 PM   #34150
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Your gain ratio is EXACTLY what I use, BV.
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