?? on using the AD1862 - jitter and LE input

I'm considering building a DAC - for multiple purposes: test signal production, custom record/playback and of course CDs

Looking at using a AD1862 and noticed in the data sheet the following:

The LSB is clocked in on the 20th clock pulse. When all data bits are loaded, a low going latch enable (LE) pulse updates the DAC input. Figure 12a illustrates the general signal requirements for data transfer for the AD1862.

Does this really mean that the output is timed by the LE latch signal and not the clock - this signal on AD's circuit comes from a digital filter IC which creates it who knows how. If I used this DAC might it not be benificial to some how create a 'low jitter' LE outside the DF (if I use a pre packaged DF) or to put another way: if the DA's output is timed by the LE signal then should this not be the signal I care most about?

Anybody out looked into this, been there, comments?

I note that the PCM1704 does this:
"The change in the output of the DAC occurs at the rising edge of the 2nd BCLK after the falling edge of WCLK.20BIT (Pin 9) DATA WORD LENGTH"
so this DAC's output is synced to the 'clock'.

Any other suggestions on DAC ics to consider - probably I will try to do balanced out and so I should probably consider DACs with balanced out or a stereo DAC which I could use that way. But it seems that the better DACs are not these - anybody have feelings otherwise?

Thanks Bill
 
Jocko,
Stupid me - I had looked in some data books I have and thought that it looked cool, you and several others made nice noises about it, did not think that since it is (was) a nice DAC that it would be obsolete. But I could of sworn I saw it listed somewhere recently... frantic retracing of steps...

Maybe if I dig into my boxes of parts, old pc boards I'll get lucky. Seems I was going down this path once before...

Bill
 
well a quick look in my junk box reveals some pcm56ks and 4 pcm1702s, but no ADs. I guess I'll use the latter, which makes info on the AD1862 redundant, though I'm still curious.
Oh and what ever is in a Sony CDP705esd - there a block of something glued to the top of the chip - no time to do a search yet and I don't have access to lots of service manuals any longer.

Bill
 

quantran

Member
2004-04-27 10:15 am
Hanoi
The AD1862 seems to be very highly rated.

Is the Ad1860 comparable to AD1862 in term of performance. They seem to be the same except for the number of bits (18 and 20). But we only have 16 bits from CDs so I guess the result would be similar.

Will the +/-12v PS give any benefit over +/-5V?
 
quantran said:
The AD1862 seems to be very highly rated.

Is the Ad1860 comparable to AD1862 in term of performance. They seem to be the same except for the number of bits (18 and 20). But we only have 16 bits from CDs so I guess the result would be similar.

Will the +/-12v PS give any benefit over +/-5V?


More "bits" coming from a digital filter.......:cool: