M2TECH JOPLIN MKIII, Руководство пользователя

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JOPLIN MKIII
384
k
H
z
/32bit ANALOG-TO-DIGITAL CONVERTER
REVISION P
R
A – APRIL 2019
Copyright © 2019, M2Tech Srl
30
M2Tech
www.m2tech.biz
8.2. Navigating the menu by the IR remote
The menu is accessed by pressing the Menu button on the remote. The first parameter
(Input gain) is displayed along with its current value.
To display other parameters, use the arrow up and arrow down buttons.
When the desired parameter is displayed, its value can be changed using the arrow left
and arrow right buttons. To confirm the new value for the current parameter, press the OK
button.
To exit the menu without changing the displayed parameter value, press the Esc button.
Anyway, the system resets to the idle state after some seconds from the last operation on
the knob.
8.3. Parameters meaning and choices
8.3.1. Input gain
The
JOPLIN MKIII
is provided with an analogue 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 MKIII
. 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 MKIII
, 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.
8.3.2. Input choice
The
JOPLIN MKIII
has two inputs: one analogue (called “line”) and one coaxial digital (called
“coax”). The use of the former is straightforward, the latter has been included to allow
users to connect a digital source to a computer which is not provided with a digital input,
making a bridge between the S/PDIF and the USB. Please note that the input sampling