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In Reply to: RE: Discrete DAC's posted by The Killer Piglet on November 11, 2016 at 23:56:27
Discrete (full native resolution/non-sigma-delta) core DACs are driven by the lack of such cores in commerical D/A chips in current production. Commercial audio D/A chip vendors have transitioned to sigma-delta conversion some years ago. There really isn't an objective performance argument in favor of full resolution converters (also commonly, and sometimes incorrectly, referred to as ladder or R-2R converters) in audio applications. The argument usually centers around subjective performance. Some DAC component vendors, such as Audio Note, have been utilizing new old stocks of full resolution converters, such as the AD1865. No doubt, dwindling stocks are driving those same vendors to develop discrete core D/A converters.
That said, producing consistently high performance discrete D/A converters are not a trivial design or manufacturing endeavor. Pretty much, all such discrete solutions will perform objectively worse than the out of production commercial IC versions. Those that do perform well are relatively costly.
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Ken Newton
Follow Ups:
...do these discrete/NOS DACs pass high resolution data untouched or do they down sample the incoming data/music to 16/44.1?
Edits: 11/12/16
The old dac chips can handle quite high sample rates. For instance, the AD1865 and PCM63 can do 8 x 44.1kHz and the TDA1541a can do 4x or 8x depending on implementation. In their original cd players of the 80s, there were oversampling chips built in so that the 44.1kHz data was oversampled before it got to the dac chip.
If the dac is set up for NOS and the input/interface device allows, a dac with one of the old dac chips can handle high resolution, i.e. max. of 8x 44.1kHz = 352.8kHz or 8 x 48kHz = 384kHz.
The input/interface device (USB to I2S, USB to SPDIF, etc) is usually the limiting factor and that is usually governed by the conversion chip (i.e. XMOS, etc) and the speed of the clocks installed.
" ...do these discrete/NOS DACs pass high resolution data untouched or do they down sample the incoming data/music to 16/44.1?"
Non-oversampling (NOS) DACs transition the data off the media directly to analog, without any other digital conversion or processing taking place. All the filtering is analog, after the D/A transition takes place.
(Downsampling to 16/44 would degrade the signal, if the native rate off the media is of higher resolution.)
Most R2R dacs handle directly up to 24/192. They will not do DSD. My dac does not down or oversample. It also has no digital or analog filters
Alan
In have an Audio-GD Master 7 which uses the old 1704 R2R dac. Sounds better to me than and Delta/Sigma dac I have ever heard. What audio note is trying to do is create a chip with the 16 resistors not on the dac chip. They are having a very hard time doing this
Alan
From what I've read, using resistors of sufficient precision to obtain 16 bits when crafting discrete DACs is an/the(?) issue. Replicating it again and again must be even harder.
Like you, I'm quite happy with my 1704 DAC any will hang onto it for as long as possible.
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
True, and in addition to the resistor accuracy challenge is the issue of maintaining that accuracy over temperature variation. There are other challeneges as well, such as minimizing glitch energy. These are challenges both of design and of manufacture.
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Ken Newton
This is also what I admired about the Philips TDA1541A, and whose execution in designs like the AMR CD77 is so noteworthy.
Do you know if such implementations were required/possible/executed with Burr Brown's DACs, by any chance?
DEM described.
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
Not the older Burr-Brown full resolution DACs, such the PCM63 or PCM1702/1704. However, the newer Burr-Brown/T.I. sigma-delta based PCM179x series DACs utilize a type of DEM called data-weighted-averaging (DWA) to convert the quantizer element inaccuracy (which otherwise produce distortion) in to random noise. See the below youtube video for an explanantion on the differences.
https://www.youtube.com/watch?v=BYLo2zRJ7FU&sns=em
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Ken Newton
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
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