🚀 go-pugleaf

In article <l6!nwj#.cornhead@netcom.com> cornhead@netcom.com (Jeff Miller) writes:

>I am interested in CD quality, 18 bit studio quality, and DAT or variable 
>rate ADC's and DAC's. Evaluation units (like the Crystal board) would be 
>nice but not strictly necessary. Serial or parallel output is fine.
>If you know of any companies offering hot ADC or DAC products, zip 
>me a telephone number, maybe a part number, won't you? I'll 
>definitely summarize and post.

My knowledge is about a year old so I'd better post so that others can
correct me. Last I had heard, Crystal was working on 18+bit parts (I've
used the CS5328 18-bit ADC). They just introduced the complementary DAC
(CS4328?). It had a built-in digital filter but it was only spec'ed for
~97 dB dynamic range. The 5328 was ok, but didn't meet their published
noise spec. Note: they claim to only need a 51 ohm resistor and .01 uF
cap as an anti-aliasing filter (sample speed is in MHz range), but I've
seen others use more extensive filtering to achieve a slightly better
S/N Ratio. Pricing was ~$50 each in 1k quantities.

UltraAnalog had 20 bit converters out. They were expensive. (Maybe 3-5
times Crystal's prices in same quantities.) A product we tested that
used the ADC had unimpressive performance except for it's ~103 dB
dynamic range (when band limited and A-weighted).

The 'hot' ADC, however, was a new 20 bit offering from Analog Devices.
Designed by a group led by Bob Adams (who developed UltraAnalog's ADC),
it used differential inputs and was quite inexpensive. (Maybe $25 each
in 1k quantities? It was, however, single channel. Still it was $ com-
petitive with Crystal, which was the goal.) I never got the chance to
play with it but think they had a development board. [Sorry, I forgot
the part number :-(]

DAC's? Used Burr-Brown's PCM1700 with NPC5803 digital filter. Quite
decent performance (>105 dB dynamic range, A-weighted, close to 100
unweighted). [BTW, BB's PCM1750 [18 bit ADC] required an anti-alias
filter. We never got good results w/ the 1750.] As mentioned, Cry-
stal only spec'ed their 4328 to ~97 dB (A-weighted). Didn't get
pricing. UltraAnalog had 18 and 20 bit DAC's, but they were also
very expensive. Not sure what Analog Devices had.

Overall, the CS5328, NPC5803, and PCM1700 gave reasonable results.
< .02% distortion 20-20k (with transformer outputs!), linear phase*,
good crosstalk rejection, very linear distortion vs. input voltage.
Dynamic range was the only real problem.

*The phase was very linear except for a step at ~10kHz. Not sure
which part caused it. Still I think the group delay was < 5 usec,
20-20k.

expecting to be corrected,
greg

gkwan@balboa.eng.uci.edu