M2TECH JOPLIN MKII, Руководство пользователя

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JOPLIN M
K
II
384
k
H
z
/32bit ANALOG-TO-DIGITAL CONVERTER
REVISION P
R
A – FEBRUARY 2015
Copyright © 2015, M2Tech Srl
53
M2Tech
www.m2tech.biz
9. Notes on equalization
9.1. Why is equalization needed for records?
When cutting a record, two problems must be faced: the dynamic of the media, which
is related to the groove width and depth, thus to the record diameter and thickness,
and the surface noise. As low frequency tones tend to cut large, deep grooves,
dynamic limits are likely to be hit due to the low frequency content of the music being
cut into the vinyl. On the other hand, high frequency tones have generally low
amplitude, thus they are likely to be covered by surface noise.
To solve the above problems, an equalization is applied to the signal before sending
it to the cutting lathe: low frequencies are attenuated to reduce their dynamic and
high frequencies are amplified to elevate them over the surface noise floor.
Of course, the reversed equalization is applied to the signal coming out of a cartridge
while reading a disc: low frequencies are amplified and high frequencies are
attenuated (together with the surface noise which becomes less apparent).
Presently, all records are cut using the RIAA curve (Figure 22), which has been
proposed as a standard back in 1954. Both low frequencies amplification and high
frequencies attenuation for playback are clearly visible.