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How good are the ISA 428 optional A/D converters? What are the specs?

We have strived to make the ISA converters to the highest possible quality to preserve the detailed sound of the mic pres after conversion. The 428 converters are a very serious rival to any other high end
converters and will provide the smooth, detailed sound you would expect from any professional ADC. The crystal used has a very low jitter (+/-10psec) for a very stable internal clock. The converter specs are:

AES and S/PDIF - 2 x 9 pin D sub (8 channel)
ADAT lightpipe (max 96 KHz) - Optical (8 channel)
Bit depth - 16, 20 and 24
Sample frequencies - 44.1, 48, 88.2, 96, 176.4 and 192 KHz
Clock - Standard word clock or 'Superclock'
s/n ratio (dynamic range) - 120dBA
THD - 0.004% (measured 1KHz sine at +18dBu)
Dithering - adaptive
Level calibration - 0dBFS equivalent to +22dBu