Hello Didier, maybe you are right, and that's not easy to find. I remember an app not from LT (Jim WIlliams?) that discussed how to build a high-accuracy DC output DAC using a Sigma Delta ADC and some logic etc. Finding a 24 bit ADC is pretty easy, ADI, TI, Linear, Maxim etc seem to offer these. One could also build a composite DAC out of two 16 bit DAC's or two 20 bit DAC's etc. The voltage reference is key to good performance here, and should have <<3ppm tempco to get anywhere near the 24 bits of accuracy. bye, Said In a message dated 2/14/2008 02:02:36 Pacific Standard Time, didier@cox.net writes: What 24 bit DAC do you have in mind? I have been looking for a standalone 24 bit DAC in a small package and have not found anything I liked :-( **************The year's hottest artists on the red carpet at the Grammy Awards. Go to AOL Music. (http://music.aol.com/grammys?NCID=aolcmp00300000002565)

Hi Said, It seems we are at the same point. I have been using a TI/Burr-Brown microprocessor with a 24 bit ADC and 8 input multiplexer (the MSC1210, which is actually advertised as a precision ADC which happens to have a full blown 8051, 32k of Flash and all the usual goodies including a long timer on the same die) , and it seems the most practical way to make a 24 bit DAC for one of those is to use two 16 bit DACs and use one ADC channel to verify and tweak the DAC as necessary. Not very elegant, but practical, as long as the other specs can be met. I have to settle on a voltage reference. Based on a posting on this or another mailing list, we have been evaluating a Thaler reference for a military project I am working on (day job) and I have been quite impressed, even though they are more intended for harsh environment than for low noise, which will not really help for this project. I have not quantified the close-in noise, but I will be using some of Bruce's recommendations to build something using my PC's sound card to measure it. All this is a relatively far-out project, but I am getting the pieces together. Didier KO4BB > -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of SAIDJACK@aol.com > Sent: Thursday, February 14, 2008 2:36 PM > To: time-nuts@febo.com > Subject: Re: [time-nuts] GPS Locked and Unlocked Performance > Comparison > > Hello Didier, > > maybe you are right, and that's not easy to find. I remember > an app not from LT (Jim WIlliams?) that discussed how to > build a high-accuracy DC output DAC using a Sigma Delta ADC > and some logic etc. > > Finding a 24 bit ADC is pretty easy, ADI, TI, Linear, Maxim > etc seem to offer these. > > One could also build a composite DAC out of two 16 bit DAC's > or two 20 bit DAC's etc. The voltage reference is key to good > performance here, and should have <<3ppm tempco to get > anywhere near the 24 bits of accuracy. > > bye, > Said > > > In a message dated 2/14/2008 02:02:36 Pacific Standard Time, > didier@cox.net > writes: > > What 24 bit DAC do you have in mind? > > I have been looking for a standalone 24 bit DAC in a small > package and have not found anything I liked :-( > > > > > > **************The year's hottest artists on the red carpet at > the Grammy > Awards. Go to AOL Music. > (http://music.aol.com/grammys?NCID=aolcmp00300000002565) > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, > go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.20.5/1279 - Release > Date: 2/14/2008 6:35 PM > > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.5/1279 - Release Date: 2/14/2008 6:35 PM