R2R ADC recordings ?

[Nada]

Some of us prefer the sound of multi-bit processing in DAC's.

 

What then about the recording? Should I be hunting out multi-bit ADC transferred music?

[davewantsmoore]

I find it difficult to even understand which AD converters are single bit or multibit these days.    They all seem to work on a combination.

 

Multibit still seems more popular ... but there's a lot of SD with large oversampling going on too.

 

 

I'll be interested to see what people say on the technicals .... Single bit seems appealing for recording IMHO ..... but I think at that end of the chain, that it matters a lot more what the recording artists are doing with their gear (choice of mics, setup, studio, performers) that what type of converter is in the box.

[hochopeper]

To answer Nada's question ... looks like you're facing an uphill battle there unfortunately, I also have no idea how you'd find the information out.

 

 

 

The rest of this is a bit TL;DR but I wrote it out and now I'm not going to delete it ...

 

 

I find it difficult to even understand which AD converters are single bit or multibit these days.    They all seem to work on a combination.

 

Multibit still seems more popular ... but there's a lot of SD with large oversampling going on too.

 

 

I'll be interested to see what people say on the technicals .... Single bit seems appealing for recording IMHO ..... but I think at that end of the chain, that it matters a lot more what the recording artists are doing with their gear (choice of mics, setup, studio, performers) that what type of converter is in the box.

 

Getting the resolution from an ADC system isn't simple. I've only recently started learning about ADC technology in more detail. Jitter is more important here than in DAC IMO. It directly impacts SNR rather than creating phase noise issues as in reproduction. Once there is jitter in ADC sampled signal, it's there forever. 

 

You're right the main suspects for high (datasheet) performance ADC in audio systems are hybrids from what I've seen too. I think this is driven by the difficulty of implementing an ADC that can resolve 24bits of resolution as the market is demanding for audio ADC chips, however the last few bits of digital resolution may never be resolved due to the analogue noise floor in the sampling system.

 

 

The three or four top line audio ADCs that I'm aware of are: ESS ES9012, Ti PCM4222, AKM AK5394, Cirrus CS5381.

 

Ti has this blurb in their datasheet for the 4222:

The PCM4222 is a two-channel, multi-bit delta-sigma (∆Σ) analog-to-digital (A/D) converter. The 6-bit outputs

from the delta-sigma modulators are routed to the digital decimation filter, where the output of the filter provides

linear PCM data. The linear PCM data are output at the audio serial port interface for connection to external

processing and logic circuitry. The multi-bit modulator outputs are also routed to a direct stream digital (DSD)

engine, which converts the multi-bit data to one-bit DSD data. The DSD data are output at a separate serial

interface, allowing both PCM and DSD data to be output simultaneously from the PCM4222. The multi-bit

modulator data may also be output directly, for use by external digital filtering and processing hardware. When

the modulator output mode is enabled, the PCM and DSD outputs are not available.

 

 

From a quick glance over the AKM datasheet, it's much the same, but doesn't give access to the multibit modulator (which is after the delta-sigma stage in all examples that I've found so far, so you're not avoiding that). 

 

The AKM has a block diagram that shows basically the functional blocks inside the chip:

 

 

 

I have a copy of the datasheet for the ESS part, it's ADC technology is not described other than to mention that it is proprietary, other specs are pretty darn impressive. I have seen measurements of each of these in well implemented DIY (some may become commercial in the future) designs and they're all pretty impressive. The ESS may have a slight edge, though it's not cheap to do it and the PCM4222 is probably the pick of the bunch for ease of implementation and the analogue stages are probably more important. 

 

I don't know as much about the Cirrus part but I've seen that some have found it a bit worse than the AKM or Ti chips (one guy designed his own Cirrus and AKM ADCs and had better results with the AKM). However the Cirrus part is used by DEQX in their systems so it certainly is no slouch.

 

 

There are other types of ADCs out there too but these are the chips I'm familiar with that are used for audio.

Edited July 9, 2013 by hochopeper

[fetischizm]

i'm not aware of any R2R audio ADC chips on the market. even MSBs discrete ADC module is multibit. the only fully 1 bit ADC I know of is the 'discrete' one that was designed by Bruno Putzeys for Grimm Audio the AD1. all audio production software is working on PCM anyway so it really doesnt present much benefit IMO except archival where you dont touch the recording at all, because every operation done on DSD adds noise.

[Nada]

I think any R2R ADC's used for digital transfers might be left over from 90's technologies.

 

Does the Pacific Microsonics 2 and an older Lavry ADC use R2R converters?

 

Ive read any HDCD's are done on a R2R ADC but is it true?

[georgehifi]

I think any R2R ADC's used for digital transfers might be left over from 90's technologies.

 

Does the Pacific Microsonics 2 and an older Lavry ADC use R2R converters?

 

Ive read any HDCD's are done on a R2R ADC but is it true?

From memory the Pacific Microsonics HDCD 1 and 2 DA/AD converters, were both mulitbit 2R2 ladder dacs, I don't know if they were discrete or not, and they were considered the pinnacle of Redbook AD or DA and still are, they command ridiculous prices still, in the recording/hi-end audio industries. I think the difference between the Two and One, is that the One  had the PMD100 hdcd chip and the Two had the PMD200 hdcd chip, both are said to sound the same, some give the nod to the later/last PMD200 

 

A good read, shootout between all the greats. http://www.gearslutz.com/board/mastering-forum/525110-hi-end-converter-shootout-blind-test.html

 

Winner by this guy was the Cranesong HEDD 192

 

 

 

Cheers George

Edited July 10, 2013 by georgehifi

[fetischizm]

as long as you dont expect to get quality output out of the redbook layer on HDCDs

 

the question is though, were the ADCs R2R multibit, or just the DAC section.

Edited July 10, 2013 by fetischizm

[Nada]

I still cant find official documentation regards true R2R ADC chips.

There are some tantalizing opinions eg

Quote: The Pacific Microsonics Model Two may be the only true multi-bit ADC in existence, capable of 24-bit. And only when material has been recorded on such a machine and then played back on a true multi-bit NOS DAC can the merits of PCM really be appreciated.

To my ears, true PCM sounds closer to the original analog source than DSD. And unless you've heard 'true PCM' as described above, you're not really in a position to judge, right?

And... www.whatsbestforum.com/showthread.php?9598-DSD-comparison-to-PCM/page11

Edited July 11, 2013 by Nada

[davewantsmoore]

capable of 24-bit

 

I wonder if that is really true (in practise).   Getting this level of signal is very difficult AFAIUI

 

 

NOS

 

I dunno.   One can argue that OS is essential for PCM to work correctly....   What I can say for sure, is we can't generalise.

Edited July 10, 2013 by davewantsmoore

[Nada]

I wonder if that is really true (in practise). 

 

Please check out the link I posted above... 

 

 

One can argue that OS is essential for PCM to work correctly..

 

One can argue anything. The interesting thing about that quote is the guy who wrote it has stated he has actually listened to the various combinations ie he is reporting his experience and has great gear rather then speculating or arguing.  So Im paying notice.

[davewantsmoore]

One can argue anything. The interesting thing about that quote is the guy who wrote it has stated he has actually listened to the various combinations ie he is reporting his experience and has great gear rather then speculating or arguing.  So Im paying notice.

 

That's great.      I've also listened to the difference between OS and NOS, both in the hardware... and in software... also, between the same DAC chips ... and between different DAC chips.

 

 

I'm not trying to have an argument.   

 

The people who say there are big differences between everything are NOT the only ones who know what they're talking about.  

 

(EDIT:   Not saying that guy does fall into that category .... just saying')

Edited July 11, 2013 by davewantsmoore

[fetischizm]

NOS ADC? ermm ...

 

I gather Dave is meaning 24 bit noise free resolution yes? in which case he is 100% correct, there is no ADC on the planet capable of 24bits, the best run around 20bits

Edited July 11, 2013 by fetischizm

[davewantsmoore]

Please check out the link I posted above..

 

Ah, cool. Thanks.     So they're not producing 24bit depths.   I would have been really surprised.

[davewantsmoore]

I gather Dave is meaning 24 bit noise free resolution yes?

 

Yes

 

 

...  but to be fair, it is an impressive ADC (AFAIUI)

Edited July 11, 2013 by davewantsmoore

[fetischizm]

Yes

 

 

...  but to be fair, it is an impressive ADC (AFAIUI)

 

yes, but its not better than whats available today IMO. with the same care in analogue front end, the ES9102, AK5394A, PCM4222, all have it beat IMO. play an HDCD on a CD player and its a horror show.

[davewantsmoore]

yes, but its not better than whats available today IMO

 

Agree.   My comment was in context with it's age.

[hochopeper]

One thing is for sure, in electronics, the hardest part to get extremely high performance from is the devices that sits between digital and analogue domain, their input /output stage and power supplies are the most susceptible.

 

The people who say there are big differences between everything are NOT the only ones who know what they're talking about.  

 

Exactly. The other challenge in this is that while people often know a part of the chain very well, few know and understand the whole chain well. So finding information that joins it all together is hard. Often people are blinded by their technical interest in a component and declare that it is most important. (An digital interface guy declares jitter important above all else, a speaker guy declares speakers important about all else, an acoustics guy declares room important about all else).

 

Finding an individual that understand the details of the whole chain: digital and analogue electronics, low level software (drivers and signal processing algorithms) as well as speaker design and acoustics is pretty rare. This means that guys from decades gone who are, in general, analogue experts, don't necessarily understand the intricacies of the newer technology. The same applies in reverse too.

 

So then we're left with people who are 'jack of all trades' and have a grasp on bits of everything but perhaps not to the minute details. Even they're not so common.

 

When an expert in one field speaks it's always important to take their comments in that context. 

 

 

 

 

The links and topic (ADC technology) are of interest to me though so thanks for that Nada and if I come across anything of interest I'll report back!

Edited July 11, 2013 by hochopeper