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I think I'll demur to a true expert like PricklyPeete on this one. I think the DI would still offer some sonic improvement, or they would not sell a version of it that has both a USB and coaxial input, for people feeding it a signal from an S/PDIF source (like a CD transport) and then going into the DAC from there. But my efforts to explain why it would improve the sound (at least in theory; all individual implementations vary) would probably not be technically literate. So we'll wait and see what someone else has to say on the subject...
..........thanks for the compliment
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This largely depends on the quality of your SPDIF output. But in most(all?) cases the DI would be noticeable improvement. All the jitter specs of SPDIF interfaces that are published (e.g. WM8805 v.s. DIR 9001) are just indications of what the chip is capable of. If the quality of the incoming signal is better, the interface chip has to make fewer corrections and the performance is better.
The output of the DI is much cleaner and low-jitter than any standard SPDIF output of a computer. Hence the input receiver has to work less hard. Resulting in a lower jitter overall.
X 2
I'll add to the above excellent info with the following.
Over the past decade computer main-board manufacturers have had little incentive to improve upon the SQ side of the "everything but the kitchen sink" motherboard designs that are getting harder to manufacturer (as speeds rise) and feature creep as well as performance expectation runs smack dab into marketplace comp, competitive MSRP pricing and unrealistic (IMO at least) consumer expectations. That being said the last 4 or 5 years motherboards have improved upon their audio chip sets to a great degree vs the days of old (not that long ago actually speaking).
My own frustrations over those years with computers in general WRT my own attempts at finding a gear combination for use as a half decent audio platform (without having to resort to spending oodles of money on Pro hardware) was made easier by concentrating not on the motherboard itself (which now have as a routine feature an SPDIF output among the other connections packed tightly around it) but by focusing on sound cards themselves. For years the only real players in this field (at the consumer level) used half baked hardware audio processors ( much like the on board sound processing on motherboards) which gave lukewarm to down right awful performance (compared to even an entry level serious audio system). For example the Creative SC series starting with the SBLive claimed some serious performance in it's marketing but upon further investigation Creative admitted that it's processor would re sample everything at 48khz regardless of the original bit/sample rate's were. The EMU 101K IIRC had a flaw in hardware that necessitated the conversion....before the X-FI based cards were introduced all Creative cards could not pass bit perfect data through their SPDIF outputs.....even so the Creative SPDIF was still better than all of the mobo SPDIF outputs I had a chance to compare. I have used mostly ASUS motherboards over the years with a few exceptions thrown in for variety. My latest board is a Asus Maximus Formula Deluxe (X38 chip set) that has a decent SPDIF header (HD Audio/SoundMAX codec) and a much improved HD audio card (PCIE type) vs the AC 97 spec that had been the standard (or sub standard IMO) for years previous....Long story shorter even the Max Formula mobo's SPDIF header with it's upgraded HD Audio hardware proved to be not much of a performer, although audibly better vs the older AC 97 spec gear for serious listening. Why ? It's pretty simple really...all of those high freq timing pathways, the fact that a computer main-board is just teeming with digital EMI/RFI etc the close proximity of the traces on the motherboard itself...the complexity of the circuit, the various PSU components all have influence over that SPDIF pathway. No amount of careful layout can isolate it enough from the other components on the motherboard ( it's a wonder the SQ from the Asus Max Formula SPDIF header is as good as it is). Getting back to the X-Fi based cards....having been duped by Creative with the SBLive series not delivering the goods (because of the EMU hardware flaw) the news that Creative had finally designed a brand new (from the ground up) audio processor that could pass data without manipulation I set about searching the usual online haunts to find out which manufacturer had the best implementation of Creative's base design optimized for audio use. I settled on the Auzen Prelude (which had a SPDIF input with AKM ADC and the all important COAX output bypassing it's internal DAC). Still with me ?
Over the short term I believe built in SPDIF headers (PC or MAC) are a valuable half decent option for casual listening,gaming, HT use but as a serious audio system the better option is to look at a sound card solution to be used solely as a transport. I have yet to upgrade to the latest I7 based PC's (I build my own PC's and have for the last 20 years) but I'm willing to bet the latest and greatest motherboard chip sets still cannot overcome the conflicting issues mentioned in the previous paragraph to enough of a degree to declare SC's obsolete. To be fair there have many generations of excellent sounding Pro Audio cards available for the last 10 years but the cost of those have been rather high and they usually require some supporting hardware (and software) that is overly complex or downright inconvenient to the average joe/jane. The cost is another factor, although entry level pro gear is reasonable you run into the same performance issue as the built in audio of motherboard's themselves...the SQ isn't up to par vs an entry level, but half decent, CDP/DVDP used as a transport. So what is the average person supposed to do ? Many fall back to the USB option which in it's own right (although promising at first look) runs into even more problems than built in audio (with it's SPDIF header). TOSlink (except ST Glass) is awful, period. The technical reasons for it's dismal performance come down to the actual interface itself...the idea behind it is ingenious and with proper materials used (ST glass) it can be just as good as SPDIF but the cost of that particular method and the lack of affordable cables for it killed off interest pretty quickly vs the far cheaper high performance COAX type. To sum it all up the best performance for my system (hardware choices) turned out to be a consumer level SC (that had to have a standard RCA SPDIF output to even be considered) used solely as a transport to my DAC. The ole "keep it simple" solution is my modus operandi when it comes to digital.
I'm fairly certain the A-gd DI would improve upon the performance of a motherboards built in SPDIF output but it won't solve the main technical issue surrounding that built in output. In my mind a better way to spend that money would be to sink it into a sound card capable of bit perfect transfer that uses as it's primary digital output an SPDIF connection (to be precise RCA COAX). I'd be even happier if a SC company would offer BNC instead of RCA.......still waiting on that one. A quality SC with that RCA output eliminates the need for a DI box altogether, simplifying the signal pathway while reducing negative impact on the quality of the signal itself. Less (manipulation via software / hardware) is more
I hope that was helpful...sorry for the long post.
Peete.
