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From: Vladimir Vassilevsky on 19 Feb 2010 21:38

Is there such DAC in the world, that would allow for:

* pure THD ~ 0.0001%, SNR is not very critical.
* frequency response up to several kHz
* DC accuracy in 10mV range


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
From: John Larkin on 19 Feb 2010 23:02
On Fri, 19 Feb 2010 20:38:12 -0600, Vladimir Vassilevsky
<nospam(a)nowhere.com> wrote:

>
>Is there such DAC in the world, that would allow for:
>
>* pure THD ~ 0.0001%, SNR is not very critical.
>* frequency response up to several kHz
>* DC accuracy in 10mV range
>
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Design Consultant
>http://www.abvolt.com


Here's 4 PPM

http://www.ti.com/lit/gpn/dsd1792a

in a "24 bit" dac. You could do some software predistortion to get
that down, conditions permitting.

There are some claimed "32 bit" audio dacs!

John

From: Martin Riddle on 19 Feb 2010 23:03


"Vladimir Vassilevsky" <nospam(a)nowhere.com> wrote in message
news:jrGdnaN679OR1uLWnZ2dnUVZ_uGdnZ2d(a)giganews.com...
>
> Is there such DAC in the world, that would allow for:
>
> * pure THD ~ 0.0001%, SNR is not very critical.
> * frequency response up to several kHz
> * DC accuracy in 10mV range
>
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultant
> http://www.abvolt.com

Look thru the Cirrus logic web site
http://www.cirrus.com/en/products/pro/areas/PA65.html
I know they made some very good linear audio DAC's in the past
(linearity wise). A lot of audio dac's are 24 bit, so 10mv should be
easy.


Cheers



From: Vladimir Vassilevsky on 20 Feb 2010 00:26


John Larkin wrote:
> On Fri, 19 Feb 2010 20:38:12 -0600, Vladimir Vassilevsky
> <nospam(a)nowhere.com> wrote:
>
>
>>Is there such DAC in the world, that would allow for:
>>
>>* pure THD ~ 0.0001%, SNR is not very critical.
>>* frequency response up to several kHz
>>* DC accuracy in 10mV range
>>
>>
> Here's 4 PPM
>
> http://www.ti.com/lit/gpn/dsd1792a
>
> in a "24 bit" dac. You could do some software predistortion to get
> that down, conditions permitting.
>
> There are some claimed "32 bit" audio dacs!

I have thought of audio DACs. Unfortunately, they have abysmal
performance as far as zero shift and gain accuracy. I will probably have
to calibrate those parameters at every measurement; that will slow down
the things considerably. As for THD, a good analog filter is would be
better for this application. The 32-bit interfaces to audio DACs/ADCs
are quite usual, leaving the 32-bit performance claims on conscience of
marketing.

Tandeming two DACs (one for DC, the other one for AC) could be an
option, however it looks like a heavyweight solution; I would rather do
everything in one DAC.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
From: Vladimir Vassilevsky on 20 Feb 2010 00:37


Martin Riddle wrote:

> "Vladimir Vassilevsky" <nospam(a)nowhere.com> wrote in message
> news:jrGdnaN679OR1uLWnZ2dnUVZ_uGdnZ2d(a)giganews.com...
>
>>Is there such DAC in the world, that would allow for:
>>
>>* pure THD ~ 0.0001%, SNR is not very critical.
>>* frequency response up to several kHz
>>* DC accuracy in 10mV range
>>
> Look thru the Cirrus logic web site
> http://www.cirrus.com/en/products/pro/areas/PA65.html
> I know they made some very good linear audio DAC's in the past
> (linearity wise). A lot of audio dac's are 24 bit, so 10mv should be
> easy.

Unfortunately, audio DACs and ADCs have poor accuracy of zero shift and
gain; because those parameters don't matter for audio applications.
Otherwise there wouldn't be a question.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
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