Thank you for sharing info of the micro iDSD! I own a nano iDSD and I am very satisfied with it. My question is, according to the PCB photo, the micro iDSD utilizes two BB DSD1793 DACs (in dual mono mode), the same as the nano iDSD, why don't you use a higher end model, such as PCM1792/1794/1795? At least those models have better specs, and are more widely used.
Fair enough question!
Why not "more modern and or better spec chip's?"
Simple. On paper they may look great. But in practice, because they do not sound particularly good to our ears.
Designing a DAC or ADC Chip is a bit of a black art. Compare it to cooking. Everyone can boil water, few can make even a passable, never mind outstanding Crème brûlée.
Many ADC/DAC Chip's that deliver outstanding performance seem to result from lucky accidents, where someone in the big corporate hierarchy got it right.
They got it right either because they knew exactly what they are doing and design for sound quality (something that is not easily, if at all "measurable"), or by sheer accident (the million monkeys, million typewriters and Shakespeare gig). In the history of digital audio there have been a number of ADC and DAC Chip's (or discrete solutions) that were outstanding.
The "exceptional sound quality DAC's cover all possible technologies.They range from antique "stacked" 4-Bit bipolar DAC's in the early Accuphase CD-Players and discrete resistor ladders in the Korean-made Fisher brand vertical loading CDP (in case you were wondering, similar to this one below) Thorsten still gets misty-eyed over the sound quality (it was uneconomic to repair in the late 90's).
They include the Cirrus Logic CS4328 and NPC SM5872 pure Bitstream (Delta Sigma) DAC's that were pioneering in the 90's.Their ranks feature stalwart multibit champions like the Philips TDA1541A (our all-time personal favourite), Burr Brown PCM63 (and it's grandson PCM1704) and the discrete Ultra Analog DAC modules. They range all the way to the original ESS ES9008 DAC (the "magic" seems to have dissipated somewhat in the ES9018 and a lot in the ES9018K2) and the gob-smackingly good (for the money) ES9023 which we use in the iDAC.
The PCM1793 and the PCM/DSD version DSD1793 are also in our view, part of this Pantheon. Despite somewhat less than outstanding technical specs, we found that a fairly simple implementation of this chip, with tube output stages and fed HD (PCM) audio was a serious challenger for a TDA1541 with tube output stage playing CD-Audio. Alas, the newer and supposedly superior TI Designed DAC's sold under the Burr Brown Brand are not their sonic equal. So we do not use them.
As for Spec's, our Thorsten has personally done the full Audio Precision 2 work-up on the final production level iDSD micro prototype (as it will be manufactured). He found that the A-Weighted SNR of the final version, with all tweaking and tuning came in at around 119dB, for a 2V analogue output level that is within a very small distance of what is physically possible.
Give the DSD1793 a really, really good PSU and operate it Dual-Mono, and you are not far off the spec's for the later stuff. Yet it sounds (to our ears) a whole lot "meatier" (read: good). And of course, it helps greatly that it does not manipulate the signal and keeps DSD and PCM as they are.
Edited by iFi audio - 6/17/14 at 11:30am