Any reference for this inner detail - perhaps the same Bob Adams presentation I've just cited? I'm specifically interested in the 'RTZ' aspect as it relates the ISI question. On probing the output of my toy AD1955, I haven't noticed that the output currents are RTZ, so I guess this is an on-chip technique only. Dual RTZ DACs are shown in the paper I've just referenced, their outputs are summed on-chip to solve the ISI problem. This still leaves ISI as a problem for the external I/V stage...
no, it is not dependent inverting or non inverting topology was used.
ability of negative feedback to reduce the distortion depends on the place where distortion been generated. Reducing distortion and noise is directly proportional to gain from summing point to place where distortions are generated. Thats why distortion(&noise) of output stage is reduced by all of loop gain, and distortion generaten in input stage is not reduced at all. (thats why when we use NFB noise of all scheme is (almost) the same as without NFB)
Read
S.I.Ageev "Superlinear amlifier"
James L. Karki "Designing for low distortion with high-speed op amps"
Bode "Network analysys and feedback amplifier design"
B. J. Lurie "Feedback Maximization"
using LPF in first analog stage (I/U) is very good but using 5534 (with low input overload capatibility) without HF&DACglitch protection (and badly compensated) and with big output bias (+4.65V) and output current from 5534 up to 20ma is completely idiotic.
no and no
FET opamp has nothing to dac monotonicity
R-2R dacs has non code dependent output resistence, only slightly code deprndent output capacitance
there are many papers and patents, for example prototype of 1852 - "A 113dB SNR OVERSAMPLING SIGMA-DELTA DAC FOR CD/DVD APPLICATION." Khiem Nguyen, Robert Adams, Karl Sweetland Analog Devices Inc., Wilmington, MA USA
I've never heard before that the ability to reduce distortion was dependent on where it was generated in the loop, its a completely new idea to me. But hey, its a feedback loop isn't it? Anyway, thanks for the references, I'll definitely have a look. Strange that Doug Self makes no mention of this in his book on power amplifier design...
No doubt about my disagreement with you here on the use of capacitance at the output of the DAC - you haven't picked up on the problem with ISI which introducing capacitance causes. I'll leave that for you to figure out - but here's a hint. Before the zero-order hold stage, there isn't a continuous time signal, there's a discrete time one. On your remaining points about misuse of 5534, fair enough.
You're totally at odds with both TI/BB and AD here. I checked a couple of datasheets (have a look at TI's DAC8811, page 8 just as one example) and they're clear that R-2R DACs have code dependent output impedance. Its obvious by inspection - each output node has a different number of resistors connected to it according to the code.
The ES9016 sabre Ultra DAC demo board from ESS Technology could be a adequate successor board. But first I must read the informations about follow weblinks:
BuffaloDAC
Test hearing of Evaluation boad of ES9008S ESS Technology
ESS Saber DAC
Audio DAC (ES9008S) | Line One Sales
ESS Technology Sabre Reference Digital to Analog Converter [audiojunkies]
CES Show Report And THE Show 2009 International Consumer Electronic Show Report and Audiophile Coverage by Enjoy the Music.com
ismosys.com
http://www.diyaudio.com/forums/digi...ce-dac-8-channel.html?perpage=25&pagenumber=1
http://www.diyaudio.com/forums/twisted-pear/128137-twisted-pear-audio-ess-sabre-buffalo-dac.html
BuffaloDAC
Test hearing of Evaluation boad of ES9008S ESS Technology
ESS Saber DAC
Audio DAC (ES9008S) | Line One Sales
ESS Technology Sabre Reference Digital to Analog Converter [audiojunkies]
CES Show Report And THE Show 2009 International Consumer Electronic Show Report and Audiophile Coverage by Enjoy the Music.com
ismosys.com
http://www.diyaudio.com/forums/digi...ce-dac-8-channel.html?perpage=25&pagenumber=1
http://www.diyaudio.com/forums/twisted-pear/128137-twisted-pear-audio-ess-sabre-buffalo-dac.html
in Self a lot of important things are not described, it is audio not a Radars, rockets etc
In all dacs especially DS we need to filtrate dac signal as soon as possible (ideally before I/U) otherwise we cant obtain dynamic linearity, and caps on the DAC output(capacitance on dac out is code dependent) create on HF zero input impedance and preventing our opamp from dac glitch etc etc etc (if we properly calculate our I/U).
ISI is completely a problem of DAC, not an analog stage after dac.
Im so sorry it is completely my mistake, i was thinking about back R-2R(now working with one of them)
Feedback and ISI...
Indeedy I started on the easiest of your references - the linked one (Karki) and find his analysis (p32) too simplistic. And another thing: what he says contradicts your claim that the input stage distortion doesn't get reduced by feedback. He says: "Distortion in a high speed op amp is attributed mainly to the intermediate and output stages". If so, then the input stage isn't contributing any distortion right?
Any references for what you're saying here? I agree that the ISI problem is a DAC problem, but adding a capacitor before the hold stage makes that capacitor a part of the DAC, not a part of the analog stage. Capacitors on the output shunt away some of the DAC's output current and prevent that reaching the I/V conversion stage - so the zero-order hold is compromised. Have you read the Hawksford paper on I/V conversion? Here's a link if not - his analysis makes the assumption that any capacitance is effectively completely charged within a single sample period. Hanging a big cap on the output renders that assumption false, especially so in OS DACs like the AD1955 where the sample period is measured in 100s of nS.
Hawksford I/V conversion AES 2000 conference paper
in Self a lot of important things are not described, it is audio not a Radars, rockets etc
Indeedy
I started on the easiest of your references - the linked one (Karki) and find his analysis (p32) too simplistic. And another thing: what he says contradicts your claim that the input stage distortion doesn't get reduced by feedback. He says: "Distortion in a high speed op amp is attributed mainly to the intermediate and output stages". If so, then the input stage isn't contributing any distortion right?Any references for what you're saying here? I agree that the ISI problem is a DAC problem, but adding a capacitor before the hold stage makes that capacitor a part of the DAC, not a part of the analog stage. Capacitors on the output shunt away some of the DAC's output current and prevent that reaching the I/V conversion stage - so the zero-order hold is compromised. Have you read the Hawksford paper on I/V conversion? Here's a link if not - his analysis makes the assumption that any capacitance is effectively completely charged within a single sample period. Hanging a big cap on the output renders that assumption false, especially so in OS DACs like the AD1955 where the sample period is measured in 100s of nS.
Hawksford I/V conversion AES 2000 conference paper
several links are dead but still available by webarchive:
previous post:
- In developing audio devices we can always find creative non standart solutions that will ensure the best sound
Articles
post #1
https://web.archive.org/web/2010030.../yulong-dah1-mark-dac-pre-amp-headphone-amps/
P.S.:
I am looking for a schematic of Yulong Audio's DAH-1
previous post:
- In developing audio devices we can always find creative non standart solutions that will ensure the best sound
Articles
post #1
https://web.archive.org/web/2010030.../yulong-dah1-mark-dac-pre-amp-headphone-amps/
P.S.:
I am looking for a schematic of Yulong Audio's DAH-1
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