Answer: The SPDIF iPurifier is a totally different design. It shared with other iPurifiers only the aluminum case and the concept, purify something very dirty, USB, DC, SPDIF or whatever it may be.
The best way to look at the SPDIF iPurifier is to see it as a modern-day take on the late 1990’s “Digital Lense” concept. Incoming SPDIF is isolated (unless optical, that is isolated any which way), then the waveform is restored using a solid-state implementation of the Valve High Definition Digital Input first seen on the AMR DP-777.
Then the restored digital signal is sent into a memory buffer. The same precision adjustable 300 femtosecond jitter clock found in the DP-777 is used to match the incoming clock average and clock out the data from the buffer – minus any jitter.
What it means is that directly plugged into the input of your DAC you get a SPDIF signal with perfect waveform and as low jitter as a high crystal clock can provide. It won’t get better than that, of course, your DAC remains the limit.
Different DAC receiver chips have different inherent jitter, from the common Cirrus Logic Chips with 200pS jitter to the AKM and TI with. To get those 50/200pS jitters you must feed them a zero jitter signal, any added jitter rides through.
Of course, the SPDIF iPurifier removes all source jitter and adds very, very little of its own.
