Arda AT1201 ADC, impressive specs

[mikep]

My personal opinion (and not that of my employers) is that extended dynamic range (lets say, beyond 118db?) is for a few key things
- Marketing
- Headroom (in ADC's)
- Volume Control (in DAC's)

what about digital microphones?  Neumann claims 130db on the D mic of theirs.  no comment from me if digital mics are a good idea, but a microphone will see unpredictable levels, all the dynamic range you can get in that case is useful.

mike p

 

[jdbakker]

Since most AD and DA chips are quite straightforward to use, I was wondering if there's something "simple" packaged like that for clocking. I mean, how would one go about implementing a basic master clock for several PCM4222 chips for the usual ranges we use. And how to interface that to the outside world so that I can tell my AES-EBU soundcard that's where my sync signal is coming from.

It depends what you're asking here.

If you only ever want to use this as your master clock then a good low-noise crystal oscillator (for MCLK) plus a divider chain (for BCLK, LRCLK etc; can be AHC logic) will do. For larger numbers of converters (even on one PCB) clock distribution gets to be nontrivial.

We had a thread about DIYing a WC output/distribution. No time to search for it now.

If you want to lock to the outside world you pretty much need to roll-your-own.

you could use a DIR9001 as a clock generator, up to 96kHz.
It'll decode the AES/EBU into data (0's) and clocks.

Yes, and you could use Y5V ceramic caps in your signal path. Both are functional solutions, both are cheap and small, both are rather suboptimal. But you knew I was going to point that out.

JDB.

 

[Kingston]

For larger numbers of converters (even on one PCB) clock distribution gets to be nontrivial.

How is this?

The rnk80 ad/da solution, which I'm sure you've seen, would need something like that. Let's say 8in 8out, that means four boards, each with their own (slaved) converter chip. I guess you mean I can't just make one good MCLK, BCLK and LRCLK source and wire it to all the boards. Besides simply wiring lengths, what should one take into account? More active components, and doing what?

 

[jdbakker]

For larger numbers of converters (even on one PCB) clock distribution gets to be nontrivial.

How is this?

As often: voltage drops caused by currents running through non-ideal ground paths.

In audio systems, clocks are (still) single-ended and referenced to ground (whatever that may be).

The rnk80 ad/da solution, which I'm sure you've seen, would need something like that. Let's say 8in 8out, that means four boards, each with their own (slaved) converter chip. I guess you mean I can't just make one good MCLK, BCLK and LRCLK source and wire it to all the boards. Besides simply wiring lengths, what should one take into account? More active components, and doing what?

You already mentioned the biggest one. Minimize wiring lengths; do the clock network before you do anything else, use solid ground planes (preferably on both sides of the PCB, stitched together with vias). Carefully review ground current paths. All of this gets harder the more converters you're driving, simply because the routing gets hairier. For bonus points don't daisy chain multiple converter's clock lines, but use one single multi-out driver chip (AHC245 or similar) and have a single line dedicated for each chip/sub-board.

It would be better if audio converter chips had differential clock inputs, like most hi-speed ADCs do nowadays. Then we could run clock lines in impedance-balanced pairs, with much the same benefits as balanced audio lines.

(the seriously OCD might consider a differential clock distribution net with a diff-to-SE converter at the ADC/DAC; in that case it's worth pondering that depending on chip-level implementation details the converter's clock input threshold level may be referenced to ground, VCC, or some AC-coupled midpoint -- manufacturers tend not to specify which. Plan B would be to have a local low-noise voltage controlled crystal oscillator right next to each ADC/DAC (/cluster), with either centralized or distributed PLLs locking these to a single frequency. I've used both approaches with various degrees of success, albeit not in audio applications).

JD "how's that for more than you ever wanted to know?" B.

 

[ppa]

I add that the clock and the clock distribution line want clean power supply to have the lowest jitter possible with these components. 
I am developing two DACs and one ADC and I use a very clean power supply for these components.

 

[Kingston]

JD "how's that for more than you ever wanted to know?" B.

Thanks! With the topic at hand it's actually "barely enough", but gave me plenty of subtopics to look into.

I add that the clock and the clock distribution line want clean power supply to have the lowest jitter possible with these components.  
I am developing two DACs and one ADC and I use a very clean power supply for these components.

Interesting. For what use are you planning these converters? What kind of features, clocking, etc?

Speaking of clean PSU's, I went nuts and built me some Jung regulators for an AD/DA testbed, even for 3.3VDC. Still have to figure out a best way to ground all of them (they're on separate PCB's) and where to reference their ground sense, or if I should leave out ground sense completely.

 

[ppa]

I add that the clock and the clock distribution line want clean power supply to have the lowest jitter possible with these components.  
I am developing two DACs and one ADC and I use a very clean power supply for these components.

Interesting. For what use are you planning these converters? What kind of features, clocking, etc?

Speaking of clean PSU's, I went nuts and built me some Jung regulators for an AD/DA testbed, even for 3.3VDC. Still have to figure out a best way to ground all of them (they're on separate PCB's) and where to reference their ground sense, or if I should leave out ground sense completely.

these DAC's are stereo for mastering with SRC system to reduce the jitter. One use the Wolfson DAC WM8742 and the second a PCM1794.
These DAC's use my opamps in the analog section (APP2055 new version), but I will do a version full IC's. I will decide if to sell these ones at regular market or DIY market.  They accept from 32k to 192k signal and will have 26 dbu out max.
The ADC use the cirrus logic CS5381 and the cirrus TX. It accept from 44k to 192k sample rate and it's stereo. It uses APP2055 new version on analog stage (four). I will decide if to sell this one at regular market or DIY market. 


Regarding the clocks I use integrated an ultra low jitter clock oscillators (1pS rms).
However, it's important having an rms jitter lower of 20pS on clock oscillator and it's not important having rms jitter values near to 1, because It's impossible to hear the difference between 1 pS  and 20 pS of rms jitter on clock oscillator, but the marketing wants the lowest jitter possible so I need to have 1pS. Moreover, the ADC and DAC IC's do not keep within their circuitry the lowest clock's jitter value.


 

Regarding the oscillators' regulators I use a BB ultra low noise regulator that supply directly the clock module, the BB is preceded an RC filter and a first regs with an LM317.

How ever each stage has its regulator so there are several IC regs in these circuits.

I like the PCM1794 and the WM DACs so I am using them.   

 

[ppa]

Regarding clock power supply my goal was to have a big rejection of the AC noise.
The lowest udible jitter has the gaussian distribution, but the AC noise often has a different distribution.
so for me was more important filtering than having a low thermal noise on the regulator output, even if this last should be low in any case. Another thing important is that the clock is a easy load for the regulator if this module has a good value decupling cap, than isn't required a regulator with a very good charge regulation.  
However, since the goal is to have the lowest jitter possible so I use a low noise regulator to supply directly the clock oscillator.
Regarding the AC noise, since the clock oscillator quiescent current is low, around 15 mA, I use for the regulator section also an RC passive filter to reduce the high freq. AC noise. I have not used an LC filter to avoid any resonances. Since there are good ceramic large capacitors it was easy to make a good RC filter for the AC noise.

   

 

[gentlevoice1]

Hi ... 

Just read this thread & it made me wonder if - since then - there's appeared an actual implementation of this A/D converter? For PC or stand-alone? Any of you know of this?

Greetings,

Jesper

 

[Samuel Groner]

As far as I know the chip has so far not left preliminary status. Audio doesn't pay well, so other work has priority for such companies.

Samuel

 

[dcollins]

As far as I know the chip has so far not left preliminary status. Audio doesn't pay well, so other work has priority for such companies.

I've been using the 1201 in an evaluation board made by Arda for some time now.  I think the part is an excellent performer and have probably mastered 200+ records with it.

They are supposed to be making a DAC chip in the future, as well.


DC

 

[tardishead]

Hey DC - have you compared it to PCM4222EVM?

 

[dcollins]

Hey DC - have you compared it to PCM4222EVM?

No, I'm afraid I haven't.


DC

 

[zenmastering]

The low-power version of this ADC is used in the new Merging Technologies interface known as 'Horus':

http://www.merging.com/products/show?product=11&page=85

I used the AT1201 eval board during the early development of the Horus...it was very good in it's early incarnation and is even better now. Arda are also excellent to deal with.

Graemme

 

[Samuel Groner]

They are supposed to be making a DAC chip in the future, as well.

In fact I was thinking about the DAC chip, not the AT1201! My apologies for the confusion, the AT1201 is out and working, of course.

Samuel

 

[dcollins]

They are supposed to be making a DAC chip in the future, as well.

In fact I was thinking about the DAC chip, not the AT1201! My apologies for the confusion, the AT1201 is out and working, of course.

The DAC is called the 1401.  I have some preliminary data on it, but I think it's still confidential. 

It's an R-2R converter, which I thought was interesting, and I hope to hear one someday as I think ARDA is a very hip company.......


DC

 

[abbey road d enfer]

what about digital microphones?  Neumann claims 130db on the D mic of theirs. 

You need to read the specs thoroughly. It's A-weighted, a good 10dB better than the actual linear measurement. Another take on this is that 16-bit can provide 105dB A-weighted DR.

 

[gentlevoice1]

Hi DC & zenmastering,

Wow! - sounds really interesting with the Arda AT-1201 evaluation board ... actually it makes me "zing" if you know this expression Somewhat flying high with positive surprise!

Should I contact Arda directly to get specs, price, availability etc. or are there other sources?

Greetings,

Jesper

 

[zenmastering]

Contact Arda directly. I have no idea about their eval board sales policy because the one I used was part of a commercial product development project.

Graemme

Hi DC & zenmastering,

Wow! - sounds really interesting with the Arda AT-1201 evaluation board ... actually it makes me "zing" if you know this expression Somewhat flying high with positive surprise!

Should I contact Arda directly to get specs, price, availability etc. or are there other sources?

Greetings,

Jesper

 

[gentlevoice1]

Hi again,

Thanks for replying. I now have contacted Ardatech directly and their evaluation board should be available although it is designed to be connected e.g. to an Audio Precision Analyzer - which I don't have. In the meantime I've found this product which I guess could connect the AT-1201 to a computer - which I have ;-). It allows for up to 50 Mbps communication each way and for those - like me - who also play with e.g. a keyboard it also has a MIDI connection.

http://www.rigisystems.net/index.php/usb-audio-development-kit.html

Best regards,

Jesper