| theBlue1:
I do indeed realize that supplying an external clock source to a converter doesn’t eliminate that converter's internal clock from the picture. I’ve read the material you point to. Unfortunately, my post wasn’t clear about how I’d actually be using a new “mobile box” with a better clock and converters in my studio. (My writing wasn’t clear because I was trying not to go into too much boring detail.)
The majority of the tracking I do in my small studio involves 4 or fewer tracks at a time. So I’d be using the new box as my main AD and DA most of the time. I did actually say “to replace (or improve) my Motu 1224.” There, “improve” was a poor word choice: I didn’t mean to imply a reclocking scenario, but simply that I wouldn’t actually get rid of the 1224. I meant to say “and improve upon” (the function it serves in the studio).
So, sorry to have woken up your bęte noire!
But before you tell your bęte to go back to sleep, you point to a situation where I would have to face reclocking issues -- for which I’d have to do some experimenting. On the less frequent occasions when I’d want to track through the 1224 at the same time as with whatever new box, presumably I’d want to use the new box’s better clock as master. Ideally, I’d want to slave the Motu PCI-424 directly. But the only dedicated sync input on the PCI-424 is a 9-pin ADAT connector. So I might want to find a little box (M-Audio maybe?) that does nothing but format conversion from Word Clock to ADAT sync.
Of course, I could connect the new box directly to the 1224’s Word Clock input; but then the PCI-424 itself would be receiving 2nd-generation clock (new box to 1224 to PCI-424) to distribute elsewhere (e.g., to my 308 and 2408, on which I have digital devices connected, not using any analog converters there). Messy.
So I just might find that in those studio situations where I want to track more at a time than the single new box can input, it might be better to keep the PCI-424 as master... hopefully not degrading the converters in the new box too much by having them clocked to the Motu system. (There’s your bęte noire.)
BUT, at the moment that scenario is a bit of a digression. My main interest is in sorting the disparities in clock jitter specs.
1) How is it that a supposedly better clock, such as in the Fireface 800, can tout a jitter spec of “<700 ps,” the Firestudio can claim ultra-low jitter at “<300 ps,” and a ten-year-old Apogee can claim only 20 ps? Where’s the line between meaningful and meaningless with respect to jitter specs?
2) Among the Traveler, Firestudio and Fireface 800, is any one considered to have a *significantly* better clock than the others?
Hoagie |