More on DF output timing
Yikes, mea culpa for not posting more details along with such a seemlingly broad statement. Was typing in a hurry as the day job keeps getting in the way of fun...
The PMD100 when in standalone mode, as with many DFs from that era, divides each 8fs output frame into 32 slices. Each frame will be filled with 16, 18, 20 or 24 bit clock pulses corresponding with number of output bits selected. The bitclock and data lines are zero stuffed after the appropriate number of bits. Deglitch goes positive 2 slices prior to bitclock/data cycles, and latch_enable goes negative one slice prior. The idea is for the critical conversion event to happen after a relative period of bit silence. Less uncertainty of "when" if everything has settled down a bit [pun time]. This works for the BB61/63, Analog Devices ladder DAC chips, and Ultra Analog modules. Does not work with BB1700/1702/1704, which convert on a positive edge of the bitclock after a negative edge of the latch_enable. Regardless, the timing of bitclock is, alas, 8 x 32 or 256fs as in the diagram from ftorres, so one would need at least a 512fs clock with correct setup/hold times to register/reclock the bitclock; and feeding a continuous clock in place of bitclock would not work, unless one was extremely lucky...maybe with 16 bit output data, so that every other sample would be zero...
One could also try asynchronous reclocking, with a 1024fs or higher clock, like 45 MHz or higher. Seems a bit whacky at first, but I would take Elso's word that it can be made to work. Probably better for 1fs non-oversampling apps.
The PMD100 does have separate core and i/o power/ground pins for a reason, to provide a lower jitter feed directly to the DAC; so if one is careful, one can register/reclock at the input of the PMD100, use separate, clean, well bypassed core and i/o supplies, and feed directly to BB1700/1702/1704. The bitclock should be short and direct for fast well defined edges, but one can experiment padding/damping the latch_enable and data lines with a 100 ohm to 1kohm series resistor.
I generally prefer sonics with dither set on, and gain scaling set analog or external with no actual scaling.
I would strongly suggest trying a transformer i/v, either passive like the Sowter 8347, or cascoded with a 1:1 SE interstage xfmr like something from Lundahl, Sowter, Audio Note.
The feedback I get from private emails is that jitter reduction, passive i/v, and clean power supplies have more of a positive effect on the sonics than the particular choice of DAC chip or module. The old adage, not what, how. But, I still like the 63...
A transformer atttenuator, such as the Sowter 9335 is a waaaay kewl thing; catch is that it does not like any DC in the primary, so feeding it directly from the cascoded DAC current is not quite the best idea. It might be ok with the 1 mA or so from the BB63, but really needs either an xfmr or a cap to block the DC. Any other reasonably priced sources of such a device that will tolerate a mA or so primary DC?
Enjoy...
