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
45
M2Tech
www.m2tech.biz
8.3. Parameters meaning and choices
8.3.1. Input gain
The
JOPLIN MKII
is provided with an analog front-end which gain can be set to 0dB or
to any value between 10dB and 65dB in 1dB steps. 0dB means that an input voltage
of 2.55Vrms produces and output of 0dBFS (that is the full dynamic of the ADC).
Sources with lower output levels (such as turntable, but also many cassette tape
recorders and also reel-to-reel tape recorders and tuners) may require a higher
sensitivity to fully exploit the dynamic of the
JOPLIN MKII
. For example, a tuner with a
nominal output voltage of 500mVrms would require a gain of 5.1, that is 14dB, to
achieve the full ADC dynamic. As well, a phono cartridge with 5mV output level would
need 32dB gain, value obtained by subtracting the numeric gain of the phono
equalization to the theoretical required gain of 54dB. 65dB gain means that the full
dynamic is achieved with an input voltage as low as 1.43mVrms. This means that
even MC cartridges with output voltages as low as 100uV, considering the additional
effect of equalization’s numeric gain, can be directly connected to the
JOPLIN MKII
, at
the cost of a slight loss of dynamic.
The optimal gain is a matter of the source output level but also of the chosen
equalization curve. Rely on the VU meter and the clip indication to set the gain to the
best setting for the used source. Too high a gain, the unit will saturate and clip and
the noise floor will be higher than desired. Too low a gain and a part of the ADC
dynamic will be lost.