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
55
M2Tech
www.m2tech.biz
2. the roll-off, that is the value of the high frequency amplification at 10kHz during
recording and attenuation during playback (16dB for RIAA);
3. the shelving frequency, that is the frequency below which the low frequency
attenuation during recording and high frequency amplification during playback
are limited to a fixed value (50Hz for RIAA).
Before the introduction of the RIAA standard curve, each recording company used
her own “secret” curve (FFRR from Decca/London, HMV, Capitol, Columbia…), with
big troubles for music lovers, because no amplifier could be provided with all
equalization circuits to accommodate all the different curves. For this reason, all
amplifiers were provided with tone controls: not to compensate speakers response
nor room acoustics, but to adapt the one and only phono curve provided with the
amp to the different curves of the various LP’s. Not only LP’s are equalized:
equalization was used for 78rpm, too, as well with great variety of choices.
A good phono preamplifier, or an ADC suitable for direct phono acquiring as is the
JOPLIN MKII
, should allow the vinyl collector to choose the right curve for each LP
pressed before 1954 (but it’s known that many recording companies adopted the
RIAA curve years after the official introduction date. It seems that some eastern
Europe labels only adopted RIAA around 1975!).
Most collectors use the RIAA curve to listen to all their records, often resulting in a
sound which is not the one really recorded on master tape. To show the reason of
that, Figure 23 on next page shows some of the most famous playback curves
superimposed on the same graph.
Differences are not subtle!
Note the different low frequency amplification due to different turnover frequencies
and the different high frequency attenuation due to different roll-offs. Also, note that