Apogee Mini-MP Manuale d'uso - Pagina 13

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Mini-MP – User's Guide
MS Recording and Playback -

Advanced Techniques

To better understand the behavior of signals when employing MS Techniques, the manner in which these
signals are routed and summed may be expressed as formulae. For example, the MS Decoding Matrix may be
expressed as:
Left Output
Right Output
or more generically as:
L
R
Thus, when the Left and Right Output are summed to mono, the result may be predicted using these formulae:
L + R
The stereo component has cancelled out while the mono component has added together, resulting in a perfect
mono reproduction of the stereo signal.
With a Mini-MP it's also possible to encode Left –Right stereo signals to Mid – Side by inputting the Left – Right
signal while the unit is in MS Mode. Keeping in mind that a 6 dB drop in level occurs between ST and MS modes
(thus the 0.5 multiplication), the Mini-MP's output may be expressed thusly:
L Out
R Out
By substituting the L and R values above with their MS expressions and doing the math, it is shown that a Mid
– Side signal is output when the decoding matrix is applied to the Left-Right input:
L Out
R Out
Now that the Mid and Side signals have been extracted from the Left – Right signal, it's possible to re-apply an
MS decoding matrix and re-adjust stereo width

Internal Adjustments

The polarity of the L(Left) and R(Right) OUT connections is determined by internal jumper P12:
when P12 is installed, Pin 2 is the "Hot" or positive pin;
when P12 is removed, Pin 3 is the "Hot" or positive pin.
To access jumper P12, remove the two top screws on the front and rear panels and carefully lift the top cover.
P12 may be found directly behind the L-R IN connections.
The L(Left) and R(Right) IN connections are always Pin 2 "HOT", as are virtually all microphones.
=
Mid Input + Side Input
=
Mid Input + (-Side Input)
=
M+ S
=
M - S
=
(M + S) + (M – S)
=
0.5 (L) + 0.5 (R)
=
0.5 (L) - 0.5 (R)
=
0.5 (M+S) + 0.5 (M-S)
=
0.5 (M+S) - 0.5 (M-S)
continued
= 2M
= M
= S
7
APOGEE ELECTRONICS