It seems like you need an Apogee Big Ben. I am a little confused why you want to pass digital signals around like this?
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Thanks for the tips. I'll look into those dacs.
Shadorne, my music is all stored as flac files on a hard drive. It gets distributed via an ethernet network to various systems (great and small) in my home. One system involves the Transporter, and others use the Slim Devices Squeezebox. These gadgets are nice in that one can browse and select anything in the music collection from the listening chair. The system involving the Transporter is superior in that it permits me to put a digital signal into the EMM dac and have it clocked at the EMM dac. Theoretically, the sound should be identical to the sound from the EMM transport. In practice, the theory appears to me to be correct. And there is no noise from the spinning transport when I use the Transporter (the EMM transports I've had do make more noise than many others). Finally, this system will accomodate hi-rez digital downloads, if only I can find a quality dac that accepts the 24 bit word length and puts out a word clock. Hence the query.
Hmmmm. The Big Ben and the Isocrone appear to be external clock devices, similar to the dcs and Esoteric external clocks. They will do the job, but I'm hoping for a solution that doesn't require an outboard clock. Perhaps one day EMM will begin to use 24 bit dacs.
I'll post my query also on the Slim Devices forum. If a solution arises over there I'll be sure to post it here.
Well, I'lll be a monkey's uncle. Reading the Esoteric and dcs web sites a bit more carefully tells me that the Esoteric and dcs dacs can be used exactly as I want...word sync out to the transport(er). And the Esoteric models (at least some of them) put out 44.1 and 48 kHz clocks, and multiples thereof, and they accept 24 bit word length. Soooo, well, uh, never mind about my question, I guess. Sorry.
I think there are two schools of logic.
1) A master clock which is precisely passed around with extremely expensive and precision circuitry to accommodate that. Studios may need this if they are to keep multiple devices and bitsreams all in sync. This is the gold plated approach - everything has to be near perfect and especially the circuits transmitting and receiving the clock signal.
2) On the simple audio reproduction side it seems that the cheap way is becoming the most popular. The cheaper approach is to reclock on the DAC. Various options exist to break the link between a lower quality S/PDIF jittery input and the output clocking on the DAC. This is probably improving all the time. The idea is that a jittery interface signal is no longer the big problem it once was with older PLL loop technology PROVIDED the designer can build the best clock and DAC circuitry to "isolate" any incoming jitter from the input (either the data is buffered or an asynchronous sample rate converter is used to physically break the clock linkage/dependency. Since it is much easier to generate an accurate clock locally on a chip close to where it is needed than to transfer that precision all around to different devices - this solution seems lowest cost.
I supect you are having difficulty finding anything but pro-audio gear to do what you ask. This is beacause you are taking the gold plated approach where everything has to be of the highest precision.
FWIW: On paper I think both approaches theoretically can work - obviously some designs will be better than others and I can't tell you which one is overall "king" (certainly not on my modest digital budget) but the reason I suspect Option 2 is winning and you cannot find a DAC with a wordclock slave input is simply because this approach is difficult to achieve and very costly and the philosophy of the "reclocking engineers" believe that "reclocking" negates the need for such costly high precision on the interfaces.
Shadorne - actually I believe most pro-audio gear uses global master clocks to synchronize the digital streams in lock-step for post-record processing, not real-time playback. It is not jitter that they are dealing with, it is synchronization of the data packets between separate gear. This can be done with a single clock that fans-out to all of the gear. Not optimum at all for playback where the clock needs to originate close to the D/A.
They usually do have a good master clock inside the A/D. This is critical.
Shadorne, to be clear, I'm looking for a 24 bit dac that has a word clock output, like the EMM. Both the Esoteric and the dcs dacs have this function. I had not recognized this at the outset; rather I had assumed that those dacs were set up to function solely as you describe in your approach #1 above.
Steve, thanks for the PM. Your thoughts might be very cost effective for me, and I'll get back to you later today.
The Esoteric dacs (with or without an external clock) would indeed provide a solution to the 24/96 gap that I have with the EMM. But I have to wonder if the impressive specifications of those sophisticated outboard master clocks translate to improved performance relative to using the internal clock of the dac as master.
I might be better off ignoring 24/96 for now!