Otherwise properly mixed sounds often suffer from a predominant solo voice (which might, of course, be the intention). Ifsuch a voice needs to be suppressed, the present circuit will do
the job admirably. The circuit is based on the fact that solo voices are
invariably situated `at the center` of the stereo recordings that are
to be mixed. Thus, voice levels in the left- and right-hand channels are
about equal. Arithmetically, therefore, left minus right equals zero;
that is, a mono signal without voice.
Vocal Eliminator Circuit Diagram
There is, however, a problem: the
sound levels of bass instruments, more particularly the double basses,
are also just about the same in the two channels. On the one hand
low-frequency sounds are virtu--ally nondirectional and on the other
hand, the recording engineers purposely use these frequencies to give a
balance between the two channels. However, the bass instruments can be
recovered by adding those appearing in the left + right signal to the
left-right signal.
The whole procedure is easily followed in the circuit
diagram. The incoming stereo signal is buffered by A1 and A2. The
buffered signal is then fed to differential amplifier A3 and
subsequently to summing amplifier A5. The latter is followed by a
low-pass filter formed by A6. You can choose between a first-order and a
second-order filter by respectively omitting or fitting C2. Listen to
what sounds best. The low-frequency signal and the difference signal are
applied to summing amplifier A4.
The balance between the two is set by
PI and P2 to individual taste. You have noticed that the circuit does
not contain input or output capacitors. you wish, output capacitors can
be added without detriment. However, adding input capacitors is not
advisable, because the consequent phase shift would adversely affect the
circuit operation.
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