Topic: SD vs R2R madness (to suck or not to suck) (Read 2219 times)

paras1te · « **on:** September 01, 2015, 02:13:44 AM »

Overlooked this, but better late than never ...

Quote from: Priidik on August 30, 2015, 09:31:15 AM

Dacs with S-D chips have been accepted at large and how good are these?
Some are acceptable, but most are sub-bar performing.

How do you know (or can prove) they are "sub-bar performing"? IMPLEMENTATION is much more important -- even if they are, ALL ELSE HELD EQUAL, "sub-bar performing" [sounding], product developers can (and do) get easily overcome that low hurdle: just improve quality of passives, get better opamps, tighten up PS/regulation.

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On top of everything let's say S-D has potential, but look what it takes to squeeze it out. 8+chips in parallel per channel in some good sounding units, manufacturing costs perhaps going over some good r-2r retail price for maybe roughly the same performance.

HUH???
If you're thinkin' 'bout that 8-chips in parallel processor, noted earlier, look closely at that post. Those are Philips TDA1387 DACs, Philips last multi DACs from the mid 1990. They are still avail. in large numbers dirt cheap, mostly from Chinese stashers (check eBay or Alibaba). And they are a jelly-bean DAC; hobbyists and DIYes like 'em 'cause of their relatively large SOIC footprint, only eight pins to solder, and low price. IMO, the latest ESS or AKM will give you better sound.

R2Rs have very real problems, including sensitively to manuf. tolerances, Johnson noise (in the ladder Rs), higher V_dd pwr/current demands, thermal/performance sensitivity. Chip manuf R&Ders -- when (initially) opting for Bitstream; later for D-S -- didn't just pull a fast one on to "keep the change". Manuf. technology has come a long way, thx to semiconductor demands by Apple/Samsung/etc. So cost-effective and sample-sample consistent AND high-performance multi R2Rs can be realized -- or NOT, judging by the $$ of the newer AD57x1's.

Oh ... BTW .... psst ... as used in a certain $12k French D/A. Interesting how often Thetas, Wadias, Spectrals, et. al. get mentioned, and better Bitstreams are forgotten.
Speaking of Theta, did I mention my closetted Chroma 396. "The 396 incorporates the hybrid Burr-Brown 18-bit/1-bit PCM67 DAC. The PCM67 converts the "upper" 10 MSB with an R2R ladder (multibit) converter and the "lower" eight LSBs with a 1-bit converter." This is an approach similar to modern D-S, which are also hybrid.

ultrabike · « **Reply #1 on:** September 01, 2015, 05:51:17 AM »

Alright. I like to think D-S is not as evil as some folks think. But this deserves it's own little space IMO. Carry on.

Judeus · « **Reply #2 on:** September 01, 2015, 05:55:13 AM »

r2r does not automatically equal better then d/s... At all period. Look at purrins dac chart.

OJneg · « **Reply #3 on:** September 01, 2015, 06:07:00 AM »

Quote from: BassDigger on August 31, 2015, 04:39:58 AM

Is jitter potentially a bigger problem for DS?

Where does audio rate, as a far as speed is concerned?

Could be mistaken here, but I recall reading somewhere that 1-bit DS D/A chips (a la ESS Sabre, etc.) are more sensitive to clock jitter than multibit (R2R, switched capacitor, etc) D/A chips

ultrabike · « **Reply #4 on:** September 01, 2015, 06:15:22 AM »

Quote from: OJneg on September 01, 2015, 06:07:00 AM

Could be mistaken here, but I recall reading somewhere that 1-bit DS D/A chips (a la ESS Sabre, etc.) are more sensitive to clock jitter than multibit (R2R, switched capacitor, etc) D/A chips

I'm not sure about clock jitter sensitivity. But 1-bit DS can have more issues than multi-bit DS, which could reflect on jitter. I'm not sure this extends to multi-bit DS vs pure R2R.

BTW. Apologies for the inconvenience due to the recent thread split and move. Just felt we should leave the "vintage multibit/R2R DACs" thread true to it's topic. Post modifications were only to the title of the post.

OJneg · « **Reply #5 on:** September 01, 2015, 06:50:40 AM »

Quote from: oultrabaick on September 01, 2015, 06:15:22 AM

I'm not sure about clock jitter sensitivity. But 1-bit DS can have more issues than multi-bit DS, which could reflect on jitter. I'm not sure this extends to multi-bit DS vs pure R2R.

BTW. Apologies for the inconvenience due to the resent thread split and move. Just felt we should leave the "vintage multibit/R2R DACs" thread true to it's topic.

Well any time you work with higher frequency signals, jitter becomes more pervasive. I would assume that working with MHz inside of the whole DS oversampling architecture is where the problem becomes more prominent.

In terms of sensitivity to that jitter, it's fairly well accepted that, for example, that SCF's (switched capacitor) on the end of a D/A chip will reduce sensitivity to clock jitter. I'm guessing that's because such a design will be able to hold its value more steady or make smoother transitions, while a 1-bit converter might act less predictably when clock jitter is encountered.

Did some brief Google research. This actually quite interesting. I suggest reading on from page 15:

http://www.ece.tamu.edu/~spalermo/docs/clock_jitter_effects_delta_sigma_modulators_saad_2012.pdf

From pg21:

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A commonly used solution to alleviate DAC sensitivity to PWJ is the switched-capacito-resistor (SCR) DAC with exponentially-decaying waveform, shown in Figure16. The exponentially-decaying waveform (Figure8) of the SCR DAC makes the amount of charge transferred to the loop per clock-cycle less dependent on the exact timing of the DAC clock-edges [4, 9].

ultrabike · « **Reply #6 on:** September 01, 2015, 07:15:45 AM »

I think the paper tackles problems with high-speed Continuous time D-S designs. I think most audio ones are Discrete time D-S designs which may not have that many problems with jitter.

Here is a paper with some discussion about it and other ADC approaches.

I also think, though not fully positive, that some good audio D-S designs are return to zero in the feedback path.

*** Corrected link address

Priidik · « **Reply #7 on:** September 01, 2015, 07:35:12 AM »

Quote from: paras1te on September 01, 2015, 02:13:44 AM

How do you know (or can prove) they are "sub-bar performing"?

I might have overflown with my statement 'most'. I know what I have heard. And I have probably not heard as many as most US pirates. Sometimes I try to generalise from my exp and knowledge of the internals, but I have been wrong before in this. That is why I am trusting my ears first and perhaps then build any mind construction of the parts playing inside.
For instance the DIY Soekris dac that I built blew my expectations away, I never thought it could rival quite expensive BMC PureDac (a dac with shit loads of tech inside), instead it destroyed the BMC. Other encounters with R-2R dacs have left me with similar impressions to different extent. So this is where I come.
S-D sound in my experience is not playing on the same level.
I'm open to like a S-D dac, I trust most pirates ears to some extent here and some guys at DIYA who have built Buffalos that sound good to them. I trust people's ears more easily than their ability to derive a conclusion for how the said unit sounds from technical viewpoint.

paras1te · « **Reply #8 on:** September 01, 2015, 10:29:12 AM »

Folks ... because of the ever-increasing power of FPGA/DSP, customized and software-based D/A conversion is likely the future...
...check out PS Audio PerfectWave or the top-end Chord DACs (YouTube has some stuff, too).

madaboutaudio · « **Reply #9 on:** September 01, 2015, 10:57:29 AM »

Quote from: paras1te on September 01, 2015, 10:29:12 AM

Folks ... because of the ever-increasing power of FPGA/DSP, customized and software-based D/A conversion is likely the future...
...check out PS Audio PerfectWave or the top-end Chord DACs (YouTube has some stuff, too).

Sorry but at the current state, chord or psaudio has not best what MSB analog or Schiit Yggdrasil or even Audio-gd Master 7 can achieve.

Author Topic: SD vs R2R madness (to suck or not to suck) (Read 2219 times)

paras1te

SD vs R2R madness (to suck or not to suck)

ultrabike

RE: SD vs R2R madness (to suck or not to suck)

Judeus

RE: SD vs R2R madness (to suck or not to suck)

OJneg

RE: SD vs R2R madness (to suck or not to suck)

ultrabike

RE: SD vs R2R madness (to suck or not to suck)

OJneg

Re: SD madness (to suck or not to suck)

ultrabike

Re: SD vs R2R madness (to suck or not to suck)

Priidik

Re: SD vs R2R madness (to suck or not to suck)

paras1te

Re: SD vs R2R madness (to suck or not to suck)

madaboutaudio

Re: SD vs R2R madness (to suck or not to suck)

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Author Topic: SD vs R2R madness (to suck or not to suck) (Read 2219 times)