From what I can tell thus far, it seems to be something like (assuming a properly tuned room):
-- 3-d input format, such as W,X,Y,Z (B-format)
-- into a closely-held mic pre (I like your idea of the pre being close to the mic, in fact I think you should patent this idea if you haven't already)
-- into the front end (all the stuff that makes it "sound good" like compressors, EQ's, etc.)
-- into a pristine A/D
-- into a solid computer with no data loss, probably through some signal carrier
-- out to a pristine D/A to monitors, and format conversion to DSD, etc.
Much of what you say is about sonics, which is a never ending debate… For example, some would prefer an analog EQ or compressor, and they are not all wrong either. It is one thing to do it before the AD conversion, but after the AD, the price (cost and sonic) is a whole other AD and DA…
Apparently from your previous post, the D/A can be a significant source. This is interesting to me because the D/A always struck me as a low-jitter process, assuming it was clocked properly to begin with. And proper clocking I have always attributed to proper calibration...bypassing the jitter characteristics of the computer and clocking the D/A directly from the clock on the A/D…
There are 3 places where even a tiny jitter (less than 100pSec) will impact the signal:
1. AD conversion jitter on the input circuitry (Sample and hold circuit)
2. AD conversion jitter on the output circuitry (input to the analog filter circuitry)
3. Sample rate converter clocks (both input and output clocks)
All issues regarding data transfer and handling can tolerate orders of magnitude more jitter, many nsec, or even tenth of nsec. There are 1000psec in a nsec.
So it is not so much about keeping things (AD, DA and computer). It is a cool idea to keep the AD and DA using the same clock, but your computer would have to be “locked to” (properly buffered) to the same clock as well. The up side of such approach is the ability to use one good internal clock for AD and DA. The down side, is loss of flexibility. Given a choice between salving the AD or the DA, I would certainly prefer the AD to get the best clock (such as internal crystal), and let the DA operate on PLL. Why? Because the AD is where you define the data. Whatever is lost in the AD is gone forever. A good AD data played on a bad DA clock (or bad DA device) can be “fixed” by changing to a good DA clock (or device).
So a question comes up--it's no surprise that each vendor builds things differently...different wiring, different connectors, etc. And each wire composition (silver, copper, cryogenic, single-crystal, etc.) and capacitors, etc. pass the information differently...and the "consumer-friendly" units, by the whole, don't factor as much sonics as production. So then to help keep the signal "pristine," but with all the correct elements, do I have to go to the trouble of re-wiring the system with common wires, etc.?
I think this was the reason I related it to the Digi I/O...because I am going to great lengths to fine-tune my signal path, and then the Digi I/O comes along as somewhat of a "transfer box" that I can really just re-wire myself, with my choice of manufacturer's philosophies.
I have a lot of friends in audio that are forever listening to types of OP amps, transistors, capacitors… chasing materials, listening again and again… I know people that would rule out bipolar transistor based amps, and others dislike FETs… It is pretty nuts out there… You can have an encyclopedia of what is mostly nonsense!
The fact is: Polystyrene caps are great for sample hold, but may be less then ideal elsewhere. Some OP amp will be very clean in one circuit configuration, and distort in another. In general, the whole issue of what material and type of electronic components work best is VERY MUCH DEPENDENT on the circuit itself.
Not unlike words in the English language, it is the way you put them together that makes a sentence. Of course it is not a perfect analogy. Of course there are well made parts and poorly made parts out there. But the key to good performance is about good use of parts as an integral part of a circuit.
Of course, most of the “quest” for better parts has been on the analog side. It started way before digital audio, and “everyone knows” that digital is at least a step away from the analog signal. Say we are looking for a X2 gain stage. As a designer, I would be very happy to have good results, and good results are no more no less than a perfect magnification by a factor of 2. Say I met the goal. Should I then care about the way it was accomplished? Was it bipolar? tube? A “piece of wood” with 2 wires and ground?
Unfortunately, in audio, too often the focus is about how one gets there, not how well the result is.
Regarding wiring that “Digi transfer box”, it is not about rewiring, it is about a Digi decision to make their hardware proprietary, like a “pass protection code”. I respected their right of intellectual property. The couple of manufactures you mentioned “broke the code” (not that difficult) and so far, Digi decided not to act on it.
In any case, it would be more than wiring a transfer box, and there is no reason to do it. The digital I/O box works fine. It is a digital data transfer box, with no AD and DA conversion.
Am I going overboard here, or should I really focus on the D/A like I think you might have suggested? Why is the D/A such a problem that it can't simply be sync'd to some baseline and do a data redundancy check?
A D/A has to be very precise in terms of converting from digital to analog. The issue is not about receiving correct data. Say you want “only” 16 bits precision. For a 10V p-p signal, there are 65536 small steps, about 150uV (micro volts). For 20 bits, each step is 1 uV. The codes change each 22uSec (micro second) for a 44.1KHz CD rate, and the voltage should follow the code very precisely…
BR
Dan Lavry
