Signal-To-Noise; System Balancing - Intelix Psychologist User Manual

Signal-to-Noise

The Psychologist Matrix is an attenuation only device, i.e. it cannot amplify signals passing
through it. When all the level controls are fully on, there is unity gain, and when fully off, there is
attenuation of –100dB. To obtain optimum audio performance of the Matrix, provide it with input
signals of +4dB or greater. Depending on whether the input is balanced or unbalanced, the maxi-
mum input level should be no more than approximately +25dB.
To maximize the signal-to-noise ratio, and to take full advantage of the performance of the Matrix,
it is important to balance the system levels with most of the gain occurring before the signal enters
the Matrix, rather than in the power amplifier afterwards. The Matrix has an absolute noise floor of
approximately –80 dB. Proper level balancing, using the signal source capability of +26 dB, can
result in signal-to-noise ratios of more than 100 dB. Using the power amp to raise signal levels,
rather than a pre-Matrix amplifier or the Matrix itself, diminishes this high level of performance.
For best performance, feed the Psychologist with direct outputs or subgroups from the main mixing
console and raise levels to about +4dB.

System Balancing

To take full advantage of the Matrix's high signal-to-noise performance follow the following steps:
♦ Drive the Matrix inputs with a signal of +4dBm to +26dBm.
♦ Set the Mini-Mixer volume controls to approximately the 2 o'clock position.
♦ Adjust the post Matrix system i.e. power amplifiers to produce the desired listening levels
in the room or zone with this nominal setting of the Matrix.
Fig. 12. Poor Signal Balancing. The drawing below shows the signal-to noise performance
when the user attenuates a +4dB signal by 50 dB through the Matrix. This scenario commonly
occurs when the user sets the Mini-Mixer controls at or below the nominal mid-point in an effort to
have maximum adjustment range. However, since the control is attenuation only, the nominal mid-
point is actually 50dB of attenuation. This setting results in the relatively poor signal-to noise ratio
seen here.
+40 dB
0 dB
SN = 65 dB
-20 dB
-50 dB
-90dB
12
Audio
Source
Signal Curve
Noise Curve
Psychologist Mixer User Manual
Matrix
Mixer
Psychologist Mixer User Manual
Amplifier
SN = 40 dB