How old is too old for a Dac?

Jond,
I'm not surprised that the Audio Note is impressing you,  it has been highly praised for many years.  Excellent design and implementation withstand  the test of time. No doubt that using Duelund CAST as my output coupling capacitors improved the Yamamoto DAC further.  I'm certain that I'd be just as impressed with the AN DAC as you are. Congratulations. 
Charles 

Spoogemonkey, I think you are wondering if you buy an older DAC, how far back can you go?  I would say that unless you select a DAC that was $5000 plus new, you probably shouldn't go back more than about 5 years. 

As noted, there have been massive improvements at the lower price points from about 7-8 years ago, and this improvement still continues, although improvements are slowing. Arguably, the best sub $500 DACs today, would probably compete with most of the sub $5000 DACs from 10 years ago. 

Take a look at Bryston, Ressonessence, Chord, etc. The younger folks seem to really like Schiit, Brooklyn, Woo Audio, etc. I just got a deal (more than 50% off) on a Meridian Director so I thought I'd give a try.  With just a few days to listen suggests it is pretty good for the price point. 

spenrock

How old is too old for a Dac?

Age with this one (more than 16 years old), doesn't come into it. As it's still one of the most sought after dac ever for converting PCM (Redbook cd 16/44 or 24/96 or DXD).

http://www.advancedaudiorentals.com/products/details/productid/64

http://www.goodwinshighend.com/manufacturers/pacific_microsonics/pacific_microsonics_model_two.htm

Cheers george

@spenrock

Though there were some useful posts in reply to my OP, your reply seems to be more of the information I was looking for. And it makes sense.

One would have to be close to a wide range of product developments over many years, and there likely many people around with that knowledge set that don’t have a dog in the hunt.

Bryston, Ressonessence, Chord... Do you mean newer ones? 

Thanks

I have a lightly-modified Oppo 103 CD player.  I have run it straight into my preamp and also through a Jolida FX DAC, Schiit Gungnir, and a Channel Island Audio DAC with an external power supply, and could discern zero difference with the inclusion of these DACs.  I had audio pals come by for the comparison and nobody could tell the difference.
I upgraded to the Oppo about 3 years ago and the sonic improvement was absolutely profound over my 6 year old Consonance tube CD player, which had been a huge improvement over my 20 year old Rotel CD player.   The Oppo CD player is, in my opinion, a glimpse of audio nirvana for small money and obviated the need for a DAC.  Whatever you do, try before you buy.