[time-nuts] yet another GPSDO design, or so

Attila Kinali attila at kinali.ch
Tue Jun 29 18:24:15 UTC 2010

On Tue, 29 Jun 2010 14:07:17 EDT
EWKehren at aol.com wrote:

> > > just bought four AD 1861 on ebay with shipping was $11  each. Will see  
> > > hat I get, but they are out there and 18 bit will  cover in my opinion most 

> > Any one interested should hold off for a day buying. I have  contacted the 
> > seller asked how many he has and what a quantity price would be.  To much 
> > interest and the price will go up. I think the market for audio  equipment 
> > replacement is shrinking and there will be more reasonable offers  out there 
> > for this device, because repair of the audio equipment is  prohibitive

> This seller has 95  AD1861 in stock. Is there a reason why they would  not 
> work for all applications. No I do not get a cut. 95 would justify to do a  
> new design but I am convinced there will be plenty more.

I don't think this is such a good deal. The AD5680 which seems to have
the better characteristics for a GPSDO application is available for
6.8USD/piece at digikey.

If going for an audio DAC, i'd go for a 24bit one like the AD1853
which costa about 13USD/piece at digikey.

But please note that these audio DACs are not necessarily the right
DACs for a GPSDO application. They have a high linearity, yes, but
the have quite a bit of drift and other nastynes, which is ok for
a audio application where voltage differences over time are not so
important, but differential non-linearity is very important.

Of course, time dependent non-linearities can be compensated by
a the control loop, but it will add to the phase noise.

			Attila Kinali

If you want to walk fast, walk alone.
If you want to walk far, walk together.
		-- African proverb

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