Measurement of R2R DAC

[Sal1950]

Just wondering if you were following the conversation and who I was referring to. Please see above. Sorry no crusades (bad knees) and no monking around either as I have not taken a vow of science, typo I meant silence.

 

[gvl]

For fun, it would be interesting to see measurements of vintage R2R from the 90-s. I think the DACs built around PCM63 or UltraAnalog chips represent the pinnacle of technology of that era. They sound surprisingly good even today, fwiw, when fed clean signal. They are oversampling designs so should not suffer much from the HF droop. Can be had relatively cheaply these days from the familiar used gear outlets.

 

[gvl]

They probably measure better than most of the Schiit R2R offerings.

They are based on 20-bit DAC chips so I'd expect them to best Schiit marginal 16-bit designs, but yes it would be interesting to see how they perform compared to the Gungnir and Yggdrasil. And yes, they typically only accept 16-bit format, in their stock form anyway.

 

[amirm]

For fun, it would be interesting to see measurements of vintage R2R from the 90-s. I think the DACs built around PCM63 or UltraAnalog chips represent the pinnacle of technology of that era. They sound surprisingly good even today, fwiw, when fed clean signal. They are oversampling designs so should not suffer much from the HF droop. Can be had relatively cheaply these days from the familiar used gear outlets.

Welcome to the forum! Any suggestion and links for a cheap one?

 

[gvl]

Welcome to the forum! Any suggestion and links for a cheap one?

Thank you. The classic models that are based on the PCM63 were the Adcom GDA-600 and the Parasound D/AC 1xxx series (1000 - 1600), the 1000 being the most straightforward with singled-ended outputs and higher models adding HDCD capability (via PMD100 digital filter vs. DF1700 in non-HDCD models), and balanced outputs/more DAC chips, the 1500/1600 used the highest-binned "K" grade chips. The UltraAnalog based designs were typically TOTL models, Adcom GDA-700, Parasound D/AC-2000, PS Audio Ultralink/Ultralink II. I'm sure there were many others from more obscure or higher-end shops but I haven't been around in the digital audio scene for that long to know them all. The Assemblage lineup is another name, but afaik they used the more modern but short-lived PCM1702/PCM1704 chips (probably last high-grade multi-bit R2R audio chips made) developed after TI acquired BurrBrown. The GDA-600 or the D/AC-1000 can be had well under $200, well, with some luck. I don't have concrete links, but if you look periodically on eBay, audiogon, craigslist, etc., I'm sure you'll find one unmolested and at a good price.

 

[amirm]

Thanks. I do plan to test my own Mark Levinson DAC with PCM1704s in there: https://audiosciencereview.com/forum/index.php?threads/amirs-todo-thread.2074/page-8#post-66373

 

[gvl]

Thanks. I do plan to test my own Mark Levinson DAC with PCM1704s in there: https://audiosciencereview.com/forum/index.php?threads/amirs-todo-thread.2074/page-8#post-66373

There you go, however the ML is in a completely different league @$6,995 in 1999 dollars with custom DSP and clock onboard, well, based on what I could quickly find about it anyways.

 

[amirm]

Yes, I couldn't be caught with anything less!

 

[Blumlein 88]

https://www.stereophile.com/content/adcom-gda-700-da-processor-measurements

GDA700 Adcom, but it used a Pacific Microsonics PMD100 chip as part of the design. Doesn't look too shabby with the old measurements.

 

[gvl]

Here is another idea. DACs based on the ancient cheapo TDA1543 chip from Philips are still making circles in the audiophile community. It is a multi-bit chip that some claim to be R2R while it is not. Regardless, pretty much all designs are DIY-grade NOS+no anti-imaging filter+passive I/V conversion. I have no doubt they all measure like crap yet they do sound pleasant due to some peculiar distortion profile that TDA1543 chips create. Heck, I'm guilty of owning one and loving it in a perverted kind of way. The kicker is that some vendors use the knowledge that the TDA1543 is messing with human brain and charge outrageous amount for their products dressing them up in fancy cases with vacuum tube embellishments. It would be interesting to compare the objective performance of these DACs and try to correlate it to prices. Some names, ordered from least to most expensive, this is not a comprehensive list but hopefully sufficient to get a sense of how deep the insanity runs.

Muse TDA1543x4 DAC
Starting Point Systems DAC3
Pro-Ject DAC Box S FL
BorderPatrol DAC
Audio Note Dac 2.1
And last but not the least, enter the Vertex Aletheia DAC-1, it sells at a fairly reasonable price of only 11,000 pound sterlings.

Buying the boutique ones would be cost-prohibitive, perhaps you can find a kind soul that can loan one to science.

 

[Deleted member 65]

Amir,
this is the bonus chip I added: Pacific Microsonics PMD100 not sure what use you could have of it, maybe a walk down the memory lane at best ... ;-)

 

[DonH56]

The old datasheet I have says the TDA1543 is a segmented DAC; unary upper (MSB) 5 bits and binary lower (lsb) 11 bits. The general architecture is that of an R2R design when compared to a delta-sigma design. Most conventional DACs are segmented to reduce matching requirements and glitches among the MSBs.

 

[Cosmik]

I think we should promote the binary weighted resistor DAC as the next big thing in audio. It has very desirable audiophile features like difficulty of design and manufacture, instability with temperature, glitches, etc. all to an even greater extent than the R-2R DAC. It could just add that audio magic that people are craving.

 

[Blumlein 88]

I think we should promote the binary weighted resistor DAC as the next big thing in audio. It has very desirable audiophile features like difficulty of design and manufacture, instability with temperature, glitches, etc. all to an even greater extent than the R-2R DAC. It could just add that audio magic that people are craving.

Would you suggest electromechanical relays do the bit switching as well. That sounds tweaky and stuff.

 

[Frank Dernie]

Would you suggest electromechanical relays do the bit switching as well. That sounds tweaky and stuff.

 

[gvl]

Would you suggest electromechanical relays do the bit switching as well. That sounds tweaky and stuff.

Nah, just go all the way and use vacuum tubes for that, because using them past the D/A conversion stage is an afterthought.

 

[gvl]

Perhaps you can get hold of a recent Metrum Acoustics DAC, they use custom-designed R2R ladder chips and claim close to 24-bit real world resolution in the latest iteration. They are NOS designs, so may not produce the cleanest spectrum, but the linearity tests would be interesting.

 

[Wombat]

Perhaps you can get hold of a recent Metrum Acoustics DAC, they use custom-designed R2R ladder chips and claim close to 24-bit real world resolution in the latest iteration. They are NOS designs, so may not produce the cleanest spectrum, but the linearity tests would be interesting.

View attachment 11724

Claim, not show? Grain of salt stuff. Or maybe subjective snort dust.

 

[gvl]

They have datasheets for their DAC modules published on their website and also sell them separately to OEMs, take it with what you see fit.

 

[amirm]

Perhaps you can get hold of a recent Metrum Acoustics DAC, they use custom-designed R2R ladder chips and claim close to 24-bit real world resolution in the latest iteration. They are NOS designs, so may not produce the cleanest spectrum, but the linearity tests would be interesting.

View attachment 11724

That graph only shows linearity to a bit more than 120 dB/20 bits though. But sure, if I can one for free to test, I will.