[Mike Rivers]

On Mar 25, 8:21 pm, "
wrote:

question for those who have experience with A/D clock design: Is there
more to it than just swapping out the crystal with a better spec'd
part?

The crystal is just part of the clock. The actual clock signal, if
this is typical of an A/D converter, comes from a phase locked loop
circuit which uses the crystal as a reference, but because of a long
time constant, has greater short term stability than the crystal
itself. Better clocks have better PLLs. So he may be using better
grade capacitor, he may change the loop gain, he may even change the
circuit. The thing about people who upgrade commercial product (like
Black Lion and Audio Upgrades) is that they study out the whole
circuit and most of the time do more than the obvious. And often the
obvious (like use a "better" op amp) requires changing or adding some
other circuit components.

The thing is that they have the schematic and you and I (or at least
I) don't. What you're paying for is what they've learned.






Due to the low cost of both the soundcards and the crystals, it would
be pretty easy to set up a comparative test. If you have more than one
card, you normally sync them up via SPDIF and choose one as the
"master clock". You could install the new crystal in one card, then
run a parallel A/D and/or D/A test, specifying a different card as the
master clock for each run. Sound good?

Great! But how do I analyze the results? Arny, I know you're familiar
with these cards- any recommendations on how I can test for jitter?
(sorry to single you out, but I've read your posts on the 1010LT, and
I figured you'd sympathize with a fellow user).

Thanks in advance for your replies- this should be interesting! (and
hopefully useful!)

-dave M.