It is necessary because the digital stream is not deemphased when going digitally out of the DAT or CD player. So if a deemphasis is not applied with a digital filter in Nuendo, there is too much treble.
I had this problem transferring an old DAT tape. It's possible to approximate the curve using an EQ plugin, but it would be better to have a dedicated solution to precisely mimic the analog de/preemphasis filters used with those CDs and DATs.
A dedicated deemphasis plugin that we could put in the control room external input inserts or on a track would be nice.
Some informations i did find about 15/50 us pre/deemphasis :
http://forums.stevehoffman.tv/threads/c ... tly.88541/
In a nutshell: to generate the correct target 15/50µs EIAJ de-emphasis (or pre-emphasis) curve for CD/DAT use the following equation:
DE(f) = 10*log(A/B)-10.4576
PRE(f) = 10*log(B/A)-0.9684
DE(f) - de-emphasis output in dB at a frequency of f Hz
PRE(f) - pre-emphasis output in dB a frequency of f Hz
f = frequency in Hz
A = 1 + 1/(H x H)
B = 1 + 1/(L x L)
H = (2 x pi x f x t(H))
L = (2 x pi x f x t(L))
t(H) = high freq. time-const (15 µs = 0.000015)
t(L) = low freq. time-const (50 µs = 0.000050)
pi = 3.1416