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In Reply to: RE: Discrete DAC's posted by The Killer Piglet on November 11, 2016 at 23:56:27
It would be hard for a discrete R2R DAC to outperform an R2R that has been miniaturized on a chip in terms of technical performance. The laser trimming of resistors in a chip based DAC is a precision that would be tough to match with "macro" scale resistors. I also notice that the chip based ones could handle higher clock speeds. I think a BB PCM1704 or PCM63 could acutally handle up to 16X oversampling...this translates into speeds up to 768Khz, which is far above 192, 256 or even 512Khz that everyone is talking about.
The one argument that I have heard that might account for a better sounding discrete R2R is that you can use "better" sounding resistors. This would of course would be difficult if not impossible to determine from measurements.
However, there might be something to it. Why, when the performance was very similar, was one 20-bit DAC chip preferred over others when their performance numbers were very similar? I am thinking also of the AD1862N, and the UA D20400A DACs that were the direct competitor of the PCM63PK. The UA was very good as was the BB and for some reason the AD didn't catch on. HOwever, the AD1865N did catch on and is beloved and used to this day in some very high end designs? Was it how the resistors sounded?? Doubtful but who knows for sure. Perhaps the artifacts of their operation gave the color to their sound as each had signficant differences in their architecture.
Interestingly, the first Accuphase DACs were discrete 16 bit implementations that were optically isolated...
Don't know if they sounded good but maybe they are overlooked gems today??
Personally, I still love my PCM63PK based Monarchy M24 DAC and my UA D20400 based Kinergetics DAC (now Lampizated for the output stage). Although, I have now heard the Lampizator Atlantic with a discrete R2R and that was very nice sounding indeed.
Follow Ups:
Agree. It would be painstakingly difficult and expensive to source extremely high precision discrete resistors especially for the lower significant bits.... AND have them all track precisely over temperature. Laser trimmed on a chip would be better all around. Going fully 'discrete' is more of a novelty in this day and age, IMHO.
Spinning Schiit:
"Forget everything you know about DACs. Yggdrasil is the world's only closed-form multibit DAC, delivering 21 bits of resolution with no guessing anywhere in the digital or analog path. We've thrown out delta-sigma D/As and traditional digital filters to preserve the original samples all the way through from input to output. Let's take a closer look:
21 Bits, No Guessing: Mission-Critical D/A Technology
When doctors are trying to diagnose whether you have gas or cancer from MRI results, or when the military is trying to ensure a missile hits an ammo dump and not a nunnery next door, they don't use "24 bit" or "32 bit" delta-sigma D/A converters. Instead, they rely on precision, multibit ladder DACs , like the Analog Devices AD5791. This allows them the bit-perfect precision they need for critical applications, rather than the guesswork of a delta-sigma. We chose this same critical technology for Yggdrasil. Following these unique D/A converters are sophisticated discrete JFET buffers and summers."
I know I am dumping my BB PCM63K based DAC anytime soon...nor my Ultranalog ones either. Interestingly, The UA dacs were discrete for the first 8 bits and then used a BB 12 bit industrial ladder DAC for the lower 12 bits.
This highlights some of the issues of a discrete, or a hybrid discrete, DAC approach. That industrial IC DAC utilized for the lower 12bits undoubtedly required hand trimmed gain scaling so to linearly match the upper 4bits. Otherwise, there would be a significant discontinuity (producing distortion) every time the signal crossed the -24dBFS level.
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Ken Newton
Edits: 11/21/16
Hi Ken,
It was the first 8 bits discrete and the last 12 IC. There was also a significant amount of supporting cicuits for deglitching etc. measurements were SOTA at that time.
Hi, morricab,Yup, the Ultra Analog DAC modules were widely regarded as state of the art at the time. However, as for every industry, the IC industry is largely driven by pressure for cost reduction. That drove the release of full resolution 20bit and 24bit DAC ICs, such as the PCM1702, AD1862 and PCM1704 over discrete or hybrid DAC modules. Cost later drove the wide scale transistion to sigma-delta DAC technology that rules today.
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Ken Newton
Edits: 11/21/16
Have you ever heard one of the old Accuphase DACs that were discrete? First they had a discrete 16 bit one and later I think a 20bit discrete DAC. Interesting that was one of the first really high end approaches and now it comes back again...kind of like tubes...and SET in particular :)
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
I have my eyes on a DC-81L, which is discrete 20bit.
with the matching DP-90 transport. Lots of PCM63s!
I guess most examples of these will be 100V, meaning step-downs and so on, but it would be lovely to find either an 81 or a 91 and renovate/revitalise them.
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
Yeah one of those would be nice!!
I am looking seriously now at the Aries Cerat Kassandra II DAC. It is using 16 AD1865N per channel with a tube/transformer coupled analog stage. 70KG of DAC!! Enormous power supply for max stability on the tube stage.
I never had opportunity to hear one of those Accuphase DACs.
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Ken Newton
"Spin", is the correct word for it. Most of that Schiit consumer sales argument is all too familiar from the audio industry. The performance needs of a missile guidance system, or of an MRI machine are different than those of an audio DAC. It's not simply a matter of those other applications having more stringent requirements, but that they have DIFFERENT requirements. Specifications good for one application are not necessarily good for the others.The notion of 'closed-form' anti-image filter is another example. Audiophiles are always trying to incorrectly apply intutive analog domain notions to the non-intuitive digital signal processing domain. The notion of the importance of retaining all the original digital sample values is an analog domain notion. All that's required for perfect signal reconstruction is the removal of all of the ultrasonc images. Retaining all of the orginal sample values is not required for perfect signal reconstruction.
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Ken Newton
Edits: 11/18/16
Maybe I misread, but the close-form isn't about anti-image but about asynchronous sample rate conversion which is used for jitter rejection, not image rejection.
Still, I can say I really like the sound. :)
Best,
Erik
Schiit's spin is pretty convincing IHMO for those not wanting delta-sigma, for whatever reason.
Like audiophile cables, DACs are overcrowding the market so turn up the SPIN !
The problem is that sales spin is often complete misinformation. On the plus side, most Schiit products don't require you to take out a second mortgage on your home to purchase, so no great harm done if a Schiit product turns out to be less satisfying than the spin had led one to hope.
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Ken Newton
A $50 wall wart switching power supply incorporating fighter jet tech!
Oh, well, I guess that no real harm can be done for $50. One thing that I will say about such ads is that they do sometimes provoke intrigue regarding the details of what exactly they are so lathered up about - LOL.
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Ken Newton
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